chloride mass balance as a method for determining long...
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Chloride mass balance as a method for determininglong-term groundwater recharge rates and
geomorphic-surface stability in arid and semi-arid regions, Whisky Flat and Beatty, Nevada
Item Type Thesis-Reproduction (electronic); text
Authors Fouty, Suzanne C.
Publisher The University of Arizona.
Rights Copyright © is held by the author. Digital access to this materialis made possible by the University Libraries, University of Arizona.Further transmission, reproduction or presentation (such aspublic display or performance) of protected items is prohibitedexcept with permission of the author.
Download date 30/05/2018 11:09:57
Link to Item http://hdl.handle.net/10150/191343
CHLORIDE MASS BALANCE AS A METHOD FOR DETERMINING LONG-TERM GROUNDWATER
RECHARGE RATES AND GEOMORPHIC-SURFACE STABILITY IN ARID AND SEMI-ARID REGIONS
WHISKY FLAT AND BEATTY, NEVADA
by
Suzanne C. Fouty
A Prepublication Manuscript Submittedto the Faculty of the
DEPARTMENT OF GEOSCIENCES
in Partial Fulfillment of the Requirementsfor the Degree of
MASTER OF SCIENCE
in the Graduate College
THE UNIVERSITY OF ARIZONA
1989
STAm.IENT BY AUTHOR
This manuscript, prepared for publication in the Journal ofHydrology and in Quaternary Research, has been submitted in partialfulfillment of requirements of an advanced degree at the Universityof Arizona and is deposited in the Anteves -Reading Room to be madeavailable to borrowers as are copies of regular theses and disserta-
tions.
Brief quotations from this manuscript are allowable withoutspecial permission, provided that accurate acknowledgement of source
is made. Requests for permission of extended quotation from orreproduction of this manuscript in whole or in part may be grantedby the head of the department, or the graduate student coordinator,when in their judgement the proposed use of the material is in the
interests of scholarship. In all other instances, however, permission
must be obtained from the author.
S IGNED:
APPROVAL BY RESEARCH ADVISORY CO4I1TEE
This manuscript has been approved for submission on the shown below:
Graduate Student Coordinator, orHead of Department
1
31 ii.,c.u1 /1(
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At the source of the longest riverThe voice of the hidden waterfall
From T.S. Eliot's "Four Quartets"
What do they do.the singers, tale-writers, dancers, painters, shapers, makers?They go there with empty hands,into the ga between.They come back with things in their hands.They go silent and come back with words, with tunes.They go into confusion and come back with patterns.They go limping and weeping, ugly and frightened,and come back with wings of the redwing hawk,and eyes of the mountain lion.
From Ursula LeGuin "Always coming home'
11
ACKNOWLEGEMENTS
. It occurred to te that if I ever expected to beidentified as a scientist, I would have to step beyond the
beginning.At the same time the exposure involved, the
vulnerability inherent In researching and writing athesis created an intensely self-confronting experience forand in me. What I learned in the process is that when werisk new possibilities we give birth to ourselves.When we stand clear of others' expectations we
define our own dimensions.
The air is cool and clear on the edge.1
The completion of my thesis would not have been possible without the helpand support of family, friends, collegues, committee members, and variousfunding agencies. To all of them, I am deeply grateful.
Thanks goes to my committee members W.B. Bull, V.R. Baker, O.K. Davis,and W.J. Stone for their review and discussions of my research. Specialthanks to W.J. Stone who was generous beyond measure with his lab, time,
ideas, and willingness to keep an open mind regarding my conclusions in lightof his own earlier work. His enthusiasm helped maintain mine.
Thanks to the U.S. Geological Survey in Carson City, Nevada who provideddrilling support for collecting Beatty samples, to Jeff Fischer for numerousdiscussions, to Pat McKinley for his chloride data, to J. Davis for hisevaluation of Whisky Flat volcanic ashes, and to G. Wilson for his discussionof my chloride profiles. Thanks to Argonne National Laboratories and theDepartment of Energy who funded a substantial part of my research the secondand third year (Contract No. 31-109-ENG-38), to the U.S. Geological NationalEarthquake Hazards' Reduction Program for funds to pay for the volcanic ashes(Contract No. 14-08-OO1-G1205), to Mineral County and the Board of CountyCommissioners for their financial and Informational support, and to WaterwiseInc. for its financial support.
Thanks to L. Ely, K. Katzer, E. WohI, and L. Goffman for their review ofmy manuscript, to K Demsey, J. O'Connor, P. Pearthree, and S. Slaff for theirhelp in the field.
A special thanks to Karen Demsey, my trusted, patient, and wonderfulfriend and fellow field partner, who probably hated that 29th soil pit, butstill dug on. Thank you for all the sharing of campsites, gnats, beautifulsunsets, lightning storms over Walker Lake seen perched high on a Pleistocenebeach, the one-pot meals which though frequently repeated never got tiring.who would have thought beans, salsa, onions and tortilla chips could taste so
111
good? Thanks for the occasional treat of kahlua and coffee as the eveninggrew still filled with quiet talk, the coyote's song and the crackle of thefire, and the inspiration to run in the cool morning air while the sun slowlycrested the eastern range. It is hard to believe It is finally finished.
A special thanks also goes to --
-- my family, who provided love and support throughout, but especially whenlight seemed far away. To mom and dad for their additional financial supportand for instilling in me a strong love for and commitment to the environment,for their own personal integrity and willingness to let me find my own pathregardless of how long and winding it seems, and for reminding me at a verycritical, frustrated moment that "Moving is not always the fastest way ofgetting someplace". Thanks also to my sister Christine who left the cool,misty summer of Seattle to come to the hot, dry desert of Nevada to be myfield assistant for four very long, but very important days.
-- Lisa and Keith, Ellen, and Karen and Jim---close friends who provided
lots of moral support and laughter, as well as places to roost when thewandering began. Their friendship has been one of the rewarding aspects ofgraduate school.
-- Steve and Peg, for the use of their home, for the ready welcome to the
weary, dirty graduate student after days in the field, for the ever-presentwood pile that could be stacked when the going got rough--I always felt that Ihad accomplished something--to the reminders that shallow was better and theintensity was sometimes best dealt with with an ice-cold beer--To Anne whodanced with me to the music, a lovely reminder that life does exist aftergraduate school, and to Tess and Nugget who guarded the night and were alwaysup for a game of fetch. To Neil and Cami, who along with Steve and Peg,shared their home and their hearts plus countless margaritas, who let me hidethe truck in their garage without batting a lash. Well as the cup said--NoGuts, No Glory... So here I finally stand, signatures in hand--Time at last topass the cup. Thanks.
-- Anne for her support first from Africa and then from here, for therenewal of a long-time friendship and her belief that no matter how bad itgot, I was still special. Her energy after 4 years in the African bush was attimes like a spring of cool water. A spirit let loose to remind me of themagic of possibility. It could also be a pain in the neck, a reminder of howtired I had become, and how my vision had narrowed. So thanks to Lou for his
irreverent sense of humor, who understood at times better than Anne, the
desire to talk about and think about anything else but the thesis.
-- J. Walsh and N. Schmidt for their support, especially over the last year,for some good hikes and some great discussions, -- and a special toast to J.Walsh who started his thesis later than I, finished first, but agonized overit just the same. Time at last to truly celebrate.
-- Cindy who entered into this adventure called graduate school at the sametime and via phone calls and occasional visits shared much humor, lightness,and perspective on an often very difficult Journey. For sharing her home when
iv
I came to Socorro to do 10-day stretches of very long and tedious lab work andmuch later the added bonus of getting to know Tony and Leon the Redbone hound.To the two of you for Paria, Hannagan Meadows, the Triathalon, for waffleswith real buttermilk and countless other meals, conversations, moments. Cindy,could the beginning have really been so long ago?
-- K. Meldahl for some initial drafting and for helping me see that lifeexisted beyond school, work, and thesis--Perhaps learned a bit late in life,but a long-term lesson.
-- the Hydrology section of Tucson Water for the use to their equipment, for
their support and friendship, and especially for their willingness to beflexible with respect to work hours as I got close to the end.
-- and to Jesse Reyes who did the final drafting of my figures and did abeautiful job.
So it is finally over. Now the hard part. The beginning of a newjourney, but one not quite as well marked. It is scary and at times lonely.The horizon appears a little too open. The trick is to find the best path.So a toast to all of us, to Cool Running, to dancing in the moonlight on aCalifornia beach, to Spring break field trips, to unexpected moments of sheerdelight and joy, to times of pain, loss, and sadness which provided theimpetus to grow and reaffirmed being alive, to coffee breaks, to longconversations, and to all the missed sunsets, hikes, and books because I wassitting in front of a computer typing this manuscript. May I never have to do
this again.
What we call the beginning is often the endAnd to make an end is to make a beginning
1 modified from Margie Adams' "Naked Keys" album.
2 from T.S. Eliot's "Four Quartets"
V
2
INTRODUCTION
We are faced with an environmental crisis. The absence of controlled-disposal
sites and environmental-protection enforcement has resulted in indiscriminate
dumping of toxic wastes and the contamination of groundwater systems. The search
for potential disposal sites, where groundwater contamination is likely to be
minimal, has led to arid and semi-arid alluvial basins, where mean annual
precipitation is low, evaporation is high, and subsurface layers frequently impede
percolation. Under these conditions, groundwater recharge through the sediments is
presumed to be very small (Winograd, 1981; Roseboom. 1983). However, few methods
exist for determining long-term groundwater recharge rates and geomorphic-surface
stability in an area. Such stability is critical for safe toxic-waste disposal.
One approach to solving this question of long-term rates and stability is the
chloride mass-balance method (Allison and Hughes, 1978; Stone, 1984, 1986; Allison
et al., 1985). This method looks at the variations of chloride concentration with
depth in relationship to precipitation and chloride input. Chloride's affinity for
water provides a direct link between the amount of water moving through a soil
profile and the amount of residual chloride at a given depth.
Whisky Flat and Beatty, Nevada were chosen to test the method and look for a
chloride signature which would indicate subsurface flow. This is important because
subsurface flow leaches chloride concentrations at depth and results in an
overestimation of recharge rates. The assumptions of the method were also
examined. In the process of the investigation, additional information was observed
to be contained within the chloride profiles besides recharge rates. The profiles
also permit calculation of minimum geomorphic-surface ages, and determination of
surface stability, and root and percolation depths.
The results are divided into three separate chapters. Chapter 1 evaluates the
1
method. Chapter 2 examInes the paleoc]Jiiatic implications of the chloride profiles
at Whisky Flat and their relevance for long-term groundwater protection, and
Chapter 3 summarizes the Beatty data. Each chapter is self-contained and the
pertinent appendices are Included.
REFERENCES
Allison, G.B., and Hughes, M.W., 1978. The use of environmental chloride and
tritium to estimate total recharge to an unconfined aquifer. Australian
Journal of Soil Research 16: 181-95.
Allison, G.B., Stone, W.J., and Hughes, M.W., 1985. Recharge in karst and dune
elements of a semi-arid landscape as Indicated by natural isotopes and
chloride. Journal of Hydrology 76: 1-5.
Roseboon, E.H., Jr., 1983, Disposal of high-level nuclear waste above the water
table in arid regions: U.S. Geological Survey CIrcular 903. 21p.
Stone, W.J., 1984. Recharge in the Salt Lake Coal Field based on chloride in the
unsaturated zone. New Mexico Bureau of Mines and Mineral Resources Open-File
Report 214.
Stone, W.J., 1986. Natural recharge in southwestern landscapes--examples from New
Mexico In "Proceedings, National Water Well Association Conference on
Southwestern Ground Water Issues," October 20-22, pp. 595-602.
Winograd, I.J., 1981, Radioactive waste disposal in thick unsaturated zones:
Science, Vol. 212, No. 4502, pp.1457-1464.
2
CHAPTER 1
EVALUATION OF THE CHLORIDE MASS-BALANCE APPROACH TO DETERMININGLONG-TERM GROUNDWATER RECHARGE RATES AND GEOMORPHIC-SURFACE STABILITY
IN ARID AND SEMI-ARID REGIONS
To be submitted to: Journal of Hydrology
TABLE OF CONTENTS
Page
ABSTRACT 1
INTRODUCTION 2
CHLORIDE MASS BALANCE 4
DISCUSSION 6
ASSUMPTIONS 6
CONSTRAINTS 9
CHLORIDE PROFILES 10
CUMULATIVE CURVES 13
RECHARGE RATES AND GEOMORPHIC-SURFACE AGE 16
SENSITIVITY ANALYSIS 17
CONCLUSIONS 19
REFERENCES 22
APPENDICES 25
ABSTRACT
The chloride mass-balance method can be used to evaluate long-term groundwater
recharge rates, geomorphic-surface ages, modern and past root and percolation
depths, and surface stability in arid and semi-arid regions. The variation of
chloride concentration with depth in the soil forms the basis of the method. This
variation is graphically portrayed as chloride versus depth and cumulative chloride
versus depth plots. Both plots have an upper zone where chloride is concentrated
by evapotranspiration and a lower zone which represents water and solute flux below
the roots.
Previous studies using the mass-balance method have assumed constant
precipitation and chloride inputs through time, and invoked piston flow as the
mechanism of water and solute transport. These assumptions are not valid in semi-
arid and arid regions, In unsaturated, heterogeneous sediments, or over thousands
of years. Uncertainties In precipitation and chloride inputs limits the precision
of long-term recharge-rate and surface-age calculations because the calculations
are highly sensitive to the precipitation and chloride inputs, and bulk density
values selected.
The chloride method should be restricted to unconsolidated sediments to
minimize the occurrence of fracture flow and runoff that complicate surface-age and
recharge calculations for consolidated sediments. Surface-age calculations, using
this method, are only valid for stable, nonaggrad.tng surfaces. Recharge
calculations are valid only in zones where chloride concentrations at depth reflect
secondary chloride.
1
INTRODUCTION
Determining long-term groundwater recharge rates in semi-arid and arid regions
is critical for groundwater protection and management. It is also difficult.
Everett (1981) and Allison (1988) reviewed various physical and chemical methods
for determining water content and water flux in the vadose zone. Many of the
physical methods are expensive and time-consuming. They also only measure the
response of soil-water content to the current climatic conditions. Modern climatic
studies show that even In the short-term (i.e. 40 years), precipitation Inputs can
vary considerably (Namias, 1959; Sharon, 1972; Winstanley, 1973; Ropelewski and
Halpert, 1986). Therefore, these methods cannot give long-term, average recharge
rates.
The other approach for determining long-term rates has been to use isotopes.
These include chloride, tritium, oxygen-18, deuterium,and carbon-14 (Marshall and
Holmes, 1979). Chloride, as an indicator of soil-water fluxes In the vadose zone,
has several advantages over other isotopes. It is a stable isotope and not
affected by the absorptive properties of most clays. Chloride Is also transported
close to the average velocity of liquid water, is extremely water-soluble, and
comparatively inexpensive to analyze. These characteristics make soil-water
chloride content highly responsive to changes in surface and subsurface moisture
conditions.
Chloride concentration tends to vary with depth in the soil. This variation
is graphically portrayed in the chloride versus depth and cumulative chloride
versus depth plots which usually have a distinctive upper and lower zone (Figure
1). These profiles, along with eight assumptions, form the basis of the chloride
mass-balance approach to determining groundwater recharge rates (Allison and
Hughes, 1978; Stone, 1984a, 1986a; Gifford, 1985; Sharma, 1988, and others).
2
a.b
Chl
orid
e co
ncen
trat
ion
(mg/
I)C
umul
ativ
e ch
lorid
e (g
/sq.
m)
00
1000
2000
3000
II
Ii
I
10-
20-
-4-, a 0
Low
er z
oneU
pper
zon
e
010
0020
0030
000
II
Upp
er z
one
10-
30 -
40
Low
er z
one
Figure 1.
Examples of
(a)
Chloride concentration versus depth plot and (b) Cumulative
chloride versus
depth plot showing major zones of accumulation- (modified from Stone,
1984
a).
30 -
40
chloride method has previously been used primarily to determine groundwater
recharge rates. However, the upper zone also permits calculation of minimum
geomorphic-surface ages, and evaluation of surface stability, and root and
percolation depths. Besides providing information on recharge potential, the lower
zone can also be used to locate zones of subsurface leaching. Chloride
concentrations in a soil profile are determined from soil samples collected on a
one-time basis.
This paper will focus on the validity of those assumptions, the sensitivity of
the chloride equations to Input values selected, the type of information provided
by the chloride profiles, and the significance of the break in slope seen In the
cumulative curve.
CHLORIDE MASS BALANCE METHOD
The chloride mass balance method relies on the salt-balance and the salt-age
equations. The salt-balance equation is used to determine groundwater recharge
rates:
R (P x Clp)/Clsw (Allison and Hughes, 1978). where (1)
R = recharge rate (mm/year), P precipitation (mm/year), Cip chloride
concentration In precipitation (mg/l), Clsw average chloride concentration in
the soil below the root zone (mg/l).
Chloride concentration In the soil samples collected in the field are
determined by lab analysis. An average Clsw is determined for the lower zone from
plots of chloride versus depth. Clp and P values are obtained from the literature
or are measured In the study area. However, other sources of chloride, besides
precipitation, such as dust from playas, weathering products of minerals, reworked
4
sediments, may make a significant contribution (Wedepohi et a).., 1969; Allison et
a.L, 1985; Fouty, 1989), especially when the region is far from the ocean (Hutton,
1976). Therefore, the Clp term is replaced by total chloride input (Cit). Eq. 1
then becomes Eq. 2.
R (P x Clt)/Clsw (2)
The salt-age equation gives the relationship between time and the amount of
chloride concentrated in the soil by evapotranspiration (Bouwer, 1980; Stone,
1984a; Matthias et al., 1988).
A = CCs/(Clt x P), where (3)
A = age (years), CCs = cumulative chloride in the soil from the surface to a given
depth (g/sq. m), Clt = total chloride input (g/cu. m).
The amount of chloride in the evapotranspiration (ET) zone can be used to
calculated a minimum geomorphic-surface age (Allison et al., 1985; Fouty, 1989),
and the timing of certain erosional events (Fouty, 1989). The narrower the
precipitation and chloride range, the better the age estimate. Previously, the
amount of chloride accumulated above a given depth had been equated with the age of
the water at that depth (Stone, 1984 a,b; Phillips and Stone, 1985). However, this
relationship requires that the assumption of piston flow be valid, which it is not
(Starr et al., 1978, 1986; Allison and Hughes, 1983; Yeh et al., 1985; McCord and
Stephens, 1987).
Analytical procedures for Eq. 2 and 3 are described by Stone (1984a, b, McGurk
and Stone, 1985). Equations used to calculate chloride concentration and
volumetric water content for field samples are listed in Appendix 1.
5
DISCUSSION
ASSUMPTIONS
Eight assumptions have previously been made when using the chloride mass
balance method. They are: (1) water movement in the vadose zone is downward under
the influence of gravity and flow is one-dimensional (piston flow); (2)
precipitation has been constant throughout time; (3) chloride concentration in
precipitation has been constant throughout time; (4) precipitation is the sole
source of chloride entering the ground (Allison and Hughes, 1978; Stone, 1984a,b);
(5) precipitation is the sole source of recharge (Stone, 1986); and (6) land-use
patterns are stable. In addition, it has been implied that (7) all of the
precipitation infiltrates into the soil, and (8) that all chloride at depth is
secondary chloride (I.e. due solely to recharge). The validity of each chloride
mass-balance assumption is discussed.
Piston flow has been invoked as a mechanism for the transport of solutions In
the unsaturated zone. However, an Increasing number of examples indicate that it
is probably the exception rather than the rule (Starr et al., 1978, 1986; Allison
and Hughes, 1983; Yeh et al., 1985; McCord and Stephens, 1987; Sharma, 1988). The
absence of piston flow as a transport mechanism eliminates any connection between
the age of water at a given depth In the unsaturated zone, and the amount of
chloride accumulated above that point. This conclusion results in reinterpreting
the break in slope seen in the cumulative curves.
Variability In annual precipitation is well-documented in recent historical
records. Investigations into the past indicate that major, long-term climatic
changes have occurred. The last major long-term, low frequency climatic change
occurred in the Pleistocene. In the western Great Basin provenance of the United
States, this change resulted in an increase in effective precipitation
6
(precipitation - evaporation; Thompson and Mead, 1981; Spauithng et al., 1983;
Wells et al., 1987). The direction and magnitude of the absolute precipitation
change in this region is debated, but clearly the use of a single, mean value does
not adequately account for precipitation variability over the last 20-30,000 years.
Chloride concentration inputs also vary as contributing sources change. Thus
chloride inputs cannot be assumed to be constant through time. Nor can
precipitation be assumed to be the sole or even primary source of chloride,
especially when the region is far from the ocean (Hutton, 1976). In addition, the
ephemeral nature of many playas makes it questionable whether modern values
estimated from bulk precipitation samples (precipitation and dust) can accurately
represent the long-term average.
The assumption that precipitation is the sole source of recharge is not a
problem, provided the method is restricted to non-irrigated areas. However, the
assumption that all precipitation contributes to recharge can be a problem,
depending on the characteristics of the area. Mean annual precipitation values
most closely estimate potential recharge for unconsolidated sediments. Even here
Infiltration will vary depending on soil porosity and permeability, topography,
storm intensity, and antecedent-moisture conditions.
The relationship between precipitation and recharge becomes even more tenuous
for consolidated sediments. Fracture flow and runoff become increasingly
important, and in some cases flow along root zones or fractures accounts for the
bulk of infiltrating waters (Allison and Hughes, 1978; Stone, 1985; Gifford, 1985;
Sharma, 1988). In the case of increased runoff, mean annual precipitation averages
can severely overestimate the amount of precipitation that contributes to recharge.
When the complication of runoff is coupled with fracture flow, it becomes very
difficult to determine a representative recharge rate for a surface.
7
Changes in vegetation type (e.g. land-use patterns) also affect the amount of
precipitation which infiltrates and has recharge potential. Differences between
the average rooting depth of the current vegetation and the upper-zone thickness
indicates a change in environment. Changes may be man-made (Peck and Hurle, 1973,
Stone, 1984a, 1988; Allison, 1988), or climatically induced (Fouty, 1989) and must
be considered in the analysis of an area.
Chloride in the upper zone is usually secondary chloride, defined as chloride
that has been added to the deposited sediments by Infiltrating surface waters.
However, chloride below the root zone may be either predominantly primary or
secondary chloride. Primary chloride is defined as chloride that exists in the
sediments at the time of deposition. The source is important if a calculated
recharge rate is to have any validity, because primary chloride indicates the
absence of recharge.
Unfortunately, primary chloride values for different lithologies are scarce
and often have a considerable range (Wedepohl et a.L, 1969). Even those listed may
not be useful because of the uncertainty in determining what they actually
represent. Chloride values In consolidated rock may represent chloride contained
in the water at the time of deposition, may record the last water that has moved
into the rock, or represent chloride coatings on reworked deposits. The amount of
primary chloride will vary depending on the lithology of the unconsolidated
sediments and their geologic history.
Whether the water in the profile is primary or secondary depends on the
permeability of the rock. Water and chloride values in low-permeable sandstones
and shales are more likely primary values. In the case of reworked eolian
sediments, primary chloride may be a significant component in the chloride total.
This needs to be addressed when determining the geomorphic-surface age in order to
8
not overestimate the age. Chloride in unconsolidated sediments will usually
contain a significant secondary component, unless recharge is nonexistent.
CONSTRAINTS
The above discussion suggests several constraints to the chloride method.
First, the uncertainty in precipitation and chloride inputs limits the precision of
long-term recharge-rates and surface-age calculations because the calculations are
highly sensitive to precipitation and chloride inputs, and bulk density values
selected. Therefore, these parameters should be assigned a range in values rather
than a single, modern average. The results will consequently provide a maximum and
minimum recharge rate for the surface and a minimum geomorphic-surface age.
Second, the method should probably be restricted to unconsolidated sediments.
This minimizes the influence of macro-pores on the water transportation, decreases
the importance of runoff, and increases the amount of precipitation likely to
infiltrate and have recharge potential. The range assigned to mean annual
precipitation is then a more accurate description of water and chloride input, and
the Implied assumption that all precipitation infiltrates is probably valid. With
increased consolidation or decreased permeability, runoff becomes significant.
This will result in an overestimation of recharge rates and an underestimation the
geomorphic-surface age. This does not preclude its use in karst topography or
semi-consolidated materials, but caution is advised in interpreting the values and
assigning them regional significance.
Finally, the salt-balance equation (2) should only be used when chloride
concentrations In the lower soil profile are secondary inputs. Primary or leached
chloride values Indicate other processes ongoing In the subsurface besides the
downward percolation of surface water, and result in an Incorrect estimation of
9
recharge. The salt-age equation (3) should be restricted to stable, nonaggrading
geomorphic surfaces. Aggrading surfaces will add chloride slugs to the upper zone
and calculations will overestimate surface age.
Despite these constraints, recent studies comparing recharge rates calculated
using chloride mass balance with chlorine-36 (Phillips and Stone, 1985), tritium
(Allison and Hughes, 1978; Edinunds et al., 1988), tritiwn, oxygen-18, and deuterium
(Allison et al., 1985; Stone, 1986a), and soil moisture studies (Fouty, 1989) are
similar.
CHLORIDE VERSUS DEPTH PROFILES
The chloride profile usually has a distinctive upper and lower zone (Figure
la). Chloride concentrations in the upper zone are determined by evapotrans-
piration (ET) and tend to decrease gradually below the ET zone, until reaching a
semi-steady state value in the lower zone. The thickness of the upper zone is a
function of root and percolation depths since evaporation in arid and semi-arid
regions with deep water tables appears to be restricted to the upper 3 in (Enfield
et al. 1973; Bower, 1978; Hillel, 1982). Concentrations in the lower zone
represent either primary chloride (deposited with the sediments), secondary
chloride (added by downward percolation of surface water), or leached values.
Controls on profile shapes are either regional in extent or localized. Water-table
depth and fluctuations, and changes in root penetration and percolation depths due
to climatic change are regional controls. Buried stream channels, local influent
stream flow, downslope movement along impermeable zones, deposition/erosion,
sediment permeability and porosity, and groundwater recharge rates are considered
local controls.
Upper-zone chloride values are used to calculate geomorphic-surface age for
10
stable, nonaggrading surfaces. Stability is determined from the shape of the upper
zone. Aggradatlon is signalled by wildly fluctuating chloride concentrations,
while a stable profile builds to a peak value and then decreases (Figure 2).
Erosional events are more difficult to determine. They require assessment of
relative surface age, information on the thickness of the chloride zone of other,
comparatively old surfaces, and an idea of the modern evapotranspiration-zone depth
(Fouty, 1989).
Evaluation of the upper zone also delineates the long-term active zone with
respect to root and percolation depths. Differences between the current rooting
depth and the thickness of the upper zone provides insight into man-made or
climatically-induced changes which may not be recorded in the historical record.
Defining this long-term active zone is critical for groundwater protection in areas
being considered as toxic-waste disposal sites if contaminants are to be prevented
from reentering the biosphere through plant interaction. If modern root and
percolation depths cannot account for the thickness of the upper zone, then past
depths from a wetter, earlier period are being recorded in the chloride profile.
Lower zone values reflect subsurface leaching mechanisms and recharge rates.
Before calculations are done, it must be determined if the chloride at depth is
secondary rather than primary. It also requires deciding whether the lower profile
has been leached by flow other than the downward percolation of surface waters.
This is critical because primary values indicate the absence of recharge, while
leaching decreases chloride concentrations and results in overestimating recharge
rates. Separation of the various scenarios requires examination of all the
profiles in the area. Based on the subsurface stratigraphy, is recharge likely?
How deep is the modern water table and is there evidence of fluctuation? What is
the porosity, permeability, and lithology of the sediments? Does the geologic
11
030
0060
0090
000
3000
6000
9000
iI
iI i
iii
iI
it
Ii
I
A B
B
Figure 2.
Tpes of Information contained within the chloride versus depth profiles:
(A) Stable upper
zone indicating a stable geomorphic surface; (B) Stable lower zone
which can be used to
calculate recharge rates; (C) Fluctuating upper zone indicating an aggrading geomorphic
surface; (D) An abrupt decrease in chloride concentration suggesting leaching, due to
subsurface flow at depth (modified from Fouty,],989).
15-I
I15
D
20-a
20-
a.S
tabl
e P
rofil
eb.
Non
stab
le P
rofil
e
Chl
orid
e co
ncen
trat
ion
(mg/
I)C
hlor
ide
conc
entr
atio
n (m
g/I)
history of the area suggest that the sediments have been reworked and what effect
would this have on the chloride concentrations? Do the chloride concentrations
decrease gradually below the ET zone and then stabilize, or is there a point where
concentration decrease abruptly, suggesting subsurface flow (Figure 2).
Just as the upper thickness of the upper zone may be recording an earlier,
wetter period, recharge rates determined from the lower zone may also record this
wetter event. This Interpretation is important because it defines a worst-case
scenario regarding the likelihood of groundwater contamination due to percolation
of surface water through buried toxic waste should the climate again become wetter.
The rate calculated also defines the best case with respect to recharge potential.
The resolution of climatic events recorded in the chloride profiles is a
function of geomorphic-surface age. Young surfaces, such as reclaimed spoil sites,
will be recording recent short-term, high frequency events. As the surface age
increases, the ability to separate out discrete events deceases rapidly as the
profile becomes a composite of various climatic events. Thus on surfaces which are
thousands of years old, only low frequency, long-term climatic changes are
discernable In the chloride profiles. An example of such an event is the increase
in effective precipitation in the Western Great Basin during the Pleistocene,
followed by ifolocene drying.
CUMULATIVE CURVES
Cumulative chloride/cumulative water curves (Figure 3) show a break in slope.
This break was previously thought to indicate increase recharge in the past (Stone,
1984a, b; Allison et al., 1985; Phillips and Stone, 1985), but actually marks the
base of the evapotranspiration zone. This interpretation is supported by a
comparison of the cumulative water and chloride curves (Figure 4). The cumulative
13
a.Chloride concentration (mg/L)
0 500 1000 1500
b.
C.
44
440.4,
Chloride concentration (mg/L)0 1000 2000
I I
Chloride concentration (mg/L)0 3000 1000 9000
E1.00I-
I,
.2 3.00
E() 4.00
20 1.00 -
Figure 3. ThIee chloride versus depth profiles and their correspondingcumulative chloride versus cumulative water curves. (a) Drillhole NVii26 (Stone, 1986b); (b) Drill hole SLCF3 (Stone, 1984b);(c) Drill hole WP.3 (Fouty, 1989). Arrows indicate location of
same data point.14
Cumulative chloride (g/sq. m)0 50 100 ISO
0.00 I I I
0.25
0.50 -
0.15 -
1.00 -
1.25 -
1.50 -
Cumulative chloride (g/sq. m)0 1000 2000
0.00
0.25 -
0.50 -
0.75 -
Cumulative chloride (g/sq. m)0 1000 2000
0.00 ' I' I
C. Cumulative water (m)
0.0 0.5 1.0 1.3
15
Figure 4. Comparison of Whisky Flat cumulative curves (Fouty, 198).(a) Cumulative chloride versus cumulative water; (b) Cumulativechloride versus depth; Cc) Cumulative water versus depth.
C. Cumulotive chloride (g/sq. m) b. Cumulative chloride (g/q. m)
0 1000 2000
water-depth plots are essentially straight lines. In contrast, the cumulative
chloride-depth and the cumulative chloride-cumulative water plots show similar
breaks in slope.
The linear relationship between cumulative water and depth (Figure 4c)
Indicates fairly uniform water contents throughout these profiles. The break in
slope seen in the cumulative chloride-cumulative water plots is a by-product of
this linear relationship, with cumulative water substituting for depth. Because
chloride is concentrated in the upper zone by evapotranspiration, the chloride
concentration/unit depth is much greater in this zone. Chloride at depth is added
only when water moves below the root zone. The differences in the frequency of
these events, and thus concentrations, results in the break in slope. Straight-
line cumulative curves are interpreted as Indicating some erosion, land-use change,
or low permeability.
Curved and straight-line chloride plots were noted by Stone (1984a) for cores
in the relatively Impermeable Cretaceous coal (Fruitland Formation), in
northwestern New Mexico. Only one hole showed a break in slope in the cumulative
curve plots. Stone suggested that the narrow chloride peak was a recent addition
due to increased chloride input from a nearby coal-fired power plant, and may have
been missed in the other drill holes because of the sampling interval. Another
explanation is that the surface material was fractured at this hole. This would
permit greater infiltration of water and chloride than at non-fractured sites.
Considering the impermeable nature of the formation, this is an equally possible
explanation of the differences in the plots from this area.
RECHARGE RATES AND GEOMORPHIC-SURFACE AGE
Once the probable source of chloride has been determined, recharge rates can
16
be calculated using Eq. 2. The recharge value represents the maximum rate achieved
during the wettest period experienced by the geomorphic surface. A long-term trend
toward aridity in a basin preserves in the chloride signature of this earlier,
higher rate. A trend towards wetter conditions will, over time, replace the old
signature with a new one. The time required to reach a new equilibrium
distribution of chloride, which reflects the new recharge conditions, varies
depending on the type and magnitude of land-use (Peck and Hurle, 1973; Stone,
1984a, b) and/or climatic change.
As mentioned earlier, geomorphic-surface ages can be calculated only for
stable, nonaggrading surfaces. If chloride and precipitation inputs cannot be
tightly constrained, then the calculated ages are restricted to defining only a
minimum time span represented by the recharge rate.
SENSITIVITY ANALYSIS
Recharge rate and geomorphic-surface age estimates are dependent on the
precipitation and chloride input, and bulk density values selected. Because these
parameters vary in time and space, they should be assigned ranges rather thai a
single value. The sensitivity of the calculated products to changes In the
variables is demonstrated in Figure 5. The ranges selected are taken from a study
done in Whisky Flat, Nevada (Fouty, 1989).
The recharge equation (2) is a chloride input/storage ratio. The storage
value Is the average chloride concentration below the upper, high chloride zone
(Figure 1). Recharge rates are proportional to chloride and precipitation inputs
and remain low, even when using large ranges, because the ratio is small in arid
regions. Long-term groundwater recharge rates at Whisky Flat range from 0.04 to
0.8 mm/year.
17
I ' I ' I ' I I
250 320 310 400 440 450
Chloride concentration in soil water (mg/L)
(b) -
E
0.4 -
10.2:P = 100 mmlyr, Clt 0.55
-- P lOC) mm/yr. Cit 0.19 mgIL
0.0I I I I
210 320 350 400 440 410
Chloride concentration in soil water (mg/L)(c)
100000 -
P = 350 mnu/yr, Cit = 0.55 mg/L
P = 0.1 m/yr, Cit = 0.55 gun3
P= 0.35 m/yr, Cit = 0.55 gun30 l II Ill I
500 1000 1200 1400 1 $00 1100 2000
Cumulative chloride (g/sq. rn)
Figure 5. Results of the sensitivity analysis. (a) Chloride concentrationin the soil water as a function of bulk density; (b) Rechargerates as a function of precipitation and totai chloride input;(c) Salt ages as a function of precipitation and total chlorideinput. Data listed in Appendix 2.
18
3P = 0.1 rn/yr. Cit = 0.19 g/n$0000-
40000-
20000-
The age equation (3) is an accumulated storage/input ratio with age inversely
proportional to input. The storage value is the amount of chloride which has
accumulated in the entire upper zone. Concentrations in this zone are high in arid
regions because of high evapotranspiration demand. Ages calculated represent a
minimum range. Estimates for one Whisky Flat surface were 5,413 to 98,105 years.
The wide range in age highlights the importance of the precipitation and chloride
inputs. In this example, the calculation provides little insight into the age of
the surface. However, it does define a minimum time span represented by the
previously calculated recharge rate, in this case approximately 5,000 years.
CONCLUSIONS
Chloride mass balance is a method for evaluating groundwater recharge rates,
geomorphic-surface ages, surface stability, root and percolation depths, and the
occurrence of subsurface flow in semi-arid and arid regions. The method has
previously incorporated six stated and two implied assumptions. Evaluation of the
assumptions concluded that piston flow is the exception rather than the rule in
arid and semi-arid regions and in heterogeneous sediments. As a result, the salt-
age equation cannot be used to calculate the age of water at a given depth.
Constant precipitation and chloride inputs through time, are also invalid, but can
be accommodated for by assigning a range to input values.
The validity of the assumption that all precipitation infiltrates into the
sediments varies considerably with permeability and porosity, topography, and
antecedent-moisture conditions. Runoff is common on consolidated and low-
permeability sediments, and infiltration is low or confined to root zones or
fractures. Recharge determined from consolidated or low permeability sediments,
19
will overestimate recharge potential and underestimate the surface age.
Besides runoff and low infiltration, it must be determined whether the
chloride represents primary, secondary, or leached values. Primary chloride at
depth Indicates the absence of recharge while leached concentrations Indicate
subsurface flow. If the distinction is not made, recharge will again be
incorrectly estimated. Secondary chloride at depth usually makes up the bulk of
the concentration for unconsolidated, permeable sediments. For these reasons, the
chloride method has a more regional significance when used for unconsolidated,
permeable sediments versus the more localized significance for consolidated or low
permeable sediments. The recharge and age calculations will vary significantly
with bulk density, precipitation, and chloride input values chosen. These
parameters, In turn, vary in time and space and should be assigned ranges rather
than single values. Recharge rates thus represent a maximum and minimum range, and
surface ages, an upper and lower minimum. Age ranges tend to be large because of
the inability to tightly constrain precipitation and chloride inputs over 20,000-
30,000 years, and thus the method cannot be used as an absolute surface-age dating
technique. However, it does define a minimum time span represented by the
calculated recharge rate provided that the calculations are restricted to stable,
nonaggrading, unconsolidated geomorphic surfaces.
Finally, the break in slope seen En many cumulative chloride/cumulative water
plots defines the base of the evapotranspiration zone, not changes in past recharge
rates as previously thought. The cumulative chloride-cumulative water relationship
is really one between cumulative chloride and depth. The absence of a break In
slope Indicates land-use changes, erosion, or low permeability sediments.
While limitations to the method exist, recharge rates can be assumed to
represents caswiahIe long-term averages provided that surfaces have been stable
20
for thousands of years, inputs are adjusted for past conditions, and chloride at
depth is secondary. Careful drill-site selection and profile analysis also permit
a reconstruction of the are&s geomorphic history and a record of changes in root
and percolation depths due to climatic change. The method is thus an important
tool for determining the worst case scenario with respect to groundwater and
biosphere contamination by buried toxic wastes, and a best case with respect to
recharge potential.
21
REFERENCES
Allison, G.B., 1988. A review of some of the physical chemical and isotopic
techniques available for estimating groundwater recharge, In Simmers, I. (Ed.),
NATO ASI, Estimation of Natural Groundwater Recharge, Series C: Mathematical and
Physical Sciences Vol. 222: 49-72.
Allison, G.B., and Hughes, M.W., 1978. The use of environmental chloride and
tritium to estimate total recharge to an unconfined aquifer. Aust. J. Soil Res.,
16: 181-95.
Allison, G.B. and Hughes, M.W., 1983. The use of natural tracers as indicators of
soil-water movement in a temperate semi-arid region. J. Hydrol. 60: 157-173.
Allison, G.B., Stone, W.J., Hughes, M.W., 1985. Recharge in karst and dune elements
of a semi-arid landscape as indicated by natural isotopes and chloride. J.
Hydrol. 76: 1-25.
Bouwer, H., 1978. Groundwater Hydrology: McGraw-Hill Book Co.
Bouwer, H., 1980. Deep percolation and groundwater management. Proc. of the Deep
Percolation Symposium, Scottsdale, Arizona. Arizona Department of Water
Resources: 13-19.
Edinunds, WJ'L, Darling, W.G., Kinniburgh, D.G., 1988, Solute profile techniques for
recharge estimation in semi-arid and arid terrain, In Simmers, I. (Ed.), NATO
ASI, Estimation of Natural Groundwater Recharge, Series C: Mathematical and
Physical Sciences Vol. 222: 139-157.
Enfield, C.G., Hsieh, J.J.C., and Warrick, A.W., 1973. Evaluation of water flux
above a deep water table using thermocouple psychrometers. Soil Sd. Soc.
America Proc. 37: 968-970.
Everett, G.L., 1981. Monitoring in the Vadose Zone: Ground Water Monitoring Review
Vol. 1, No. 2: 44-51.
Fouty, S.C., 1989. Paleoclimatic implications of chloride profile shapes:
Applications for long-term groundwater protection, Whisky Flat, Nevada (Chapter
2), In Chloride Mass Balance as a method for determining long-term groundwater
recharge rates and geomorphic-surface stability, Whisky Flat and Beatty, Nevada.
M.S. thesis, University of Arizona, Tucson.
Gifford, S.K., III, 1985. Use of chloride and chlorine isotopes in the unsaturated
zone to characterize recharge at the Nevada Test Site. M.S. thesis, University
of Arizona, Tucson.
Hillel, D., 1982. Introduction to Soil Physics. Academic Press Inc.
Hutton, J.T., 1976. Chloride in rainwater in relation to distance from ocean.
Search, Vol 7, No. 5: 207-208.
22
Marshall, T.J., and Holmes, J.W., 1979. Soil Physics: Cainbrldge CambridgeUniversity Press.
Matthias, A.D., Hassan, H.M., Yu-Qi flu, Watson, J.E., and Warrick, A.W., 1986.Evapotranspiration estimates derived from subsoil salinity data. J. Hydrol. 85:209-223.
McCord, J.T. and Stephens, D.B., 1987. Lateral moisture flow beneath a sandyhilislope without an apparent impeding layer. Hydrological Processes, Vol. 1:225-238.
McGurk, B.E. and Stone, W.J., 1985. Evaluation of laboratory procedures fordetermining soil-water chloride. New Mexico Bureau of Mines and MineralResources Open-File Report 215.
Namias, J., 1959. Recent seasonal Interactions between North Pacific waters and theoverlying atmospheric circulation. J. of Geophysical Research, Vol. 4, No. 6:631-646.
Peck A.J. and Hurle, D.H., 1973. Chloride balance of some farmed and forestedcatchments in southwestern Australia. Water Resources Research, Vol 9, No. 3:648-657.
Phillips, F.M. and Stone, W.J., 1985. Chemical considerations in ground-waterrecharge. Proceedings, Symposium on Water and Science, New Mexico WaterResources Research Institute, Report 182: 109-126.
Ropelewski, C.F. and Halpert, M.S., 1986. North American precipitation andtemperature patterns associated with the El Nino/Southern Oscillation (ENSO).Monthly Weather Review 114: 2352-2362.
Sharma, M.L., 1988. Recharge estimation from the depth-distribution ofenvironmental chloride in the unsaturated zone - western Australian examples. InSimmers, I. (Ed.), NATO ASI, Estimation of Natural Groundwater Recharge, SeriesC: Mathematical and Physical Sciences Vol. 222: 159-173.
Sharon, B., 1972. The spottiness of rainfall In a desert area. J. Hydrol. 17: 161-175.
Spaulding, W.G., Leopold, E.B., and Van Devender, T.R., 1983. Late Wisconsinpaleoecology of the American Southwest. In Late Quaternary Environments of theUnited States, Vol. 1 -- The Late Pleistocene (H.E. Wright and S.C. Porter,Eds.), 259-293.
Starr, J.L., DeRoo, H.C., Fink, C.R., and Parlange, J.-Y., 1978. Leachingcharacteristics of a layered field soil. Soil Sd. Soc. of America J., Vol. 42,No. 3: 386-391.
Starr, J.L., Parlange, J.-Y., and Frink, C.R., 1986. Water and chloride movementthrough a layered field soil: Soil Sci. Soc. of America J. 50: 1384-1390.
23
Stone, W.J., 1984a. Preliminary estimates of recharge at the Navajo Mine based on
chloride in the unsaturated zone. New Mexico Bureau of Mines and MineralResources Open-File Report 213.
Stone, W.J., 1984b. Recharge in the Salt Lake Coal Field based on chloride in the
unsaturated zone. New Mexico Bureau of Mines and Mineral Resources Open-FileReport 214.
Stone, W.J., 1985. Recharge through caicrete. International Assoc. of
Hydrogeologists Memoirs, Vol. xviii, Part 1, Proceedings: 395-404.
Stone, W.J., 1986a. Natural recharge in southwestern landscapes -- examples fromNew Mexico In "Proceedings, National Water Well Association Conference on
Southwestern Ground Water Issues," October 20-22, 595-602.
Stone, W.J., 1986b. Phase-Il recharge study at the Navajo Mine based on chloride,stable isotopes, and tritium in the unsaturated zone. New Mexico Bureau of Minesand Mineral Resources Open-File Report 216.
Stone, W.J., 1988. Recovery of moisture/solute profiles in reclaimed coal-mine
spoil, northwest New Mexico. Proceedings, National Water Well Association Focus
Conference on Southwest Ground Water Issues, Albuquerque: 523-545.
Thompson, R.S. and Mead, J.I., 1982. Late Quaternary environments and biogeography
in the Great Basin. Quaternary Research 17, 39-55.
Wedepohi, K., Correns, C., Shaw, D., Turekian, K., and Zemann, J., 1969. Handbookof Geochemistry: Chapter 17--Chlorine. Apringer-Verlag Berlin-Heidelberg (Pubs.).
Wells, S.G., McFadden, L.D., and Dohrenwend, J.C., 1987. Influence of LateQuaternary climatic changes on geomorphic and pedogenic processes on a desertpiedmont, eastern Mojave Desert, California. Quaternary Research 27: 130-146.
Winstanley, D. 1973. Rainfall patterns and general atmospheric circulation. Nature
245: 190-194.
Yeh, T.-C. Jim, Gelhar, L.W., Gutjahr, A.L., 1985. Stochastic analysis of
unsaturated flow in heterogeneous soils 3. Observations and Applications. Water
Resources Research, Vol. 21, No. 4: 465-471.
24
1Stone, 1986; written communication
APPENDIX 1
EQUATIONS USED IN THE COMPUTER PROGRAMS1
CHLORIDE IN THE SOIL WATER (CLsw)
Clsw = [Cle X (Wtr added/Dry Wt)}I {[(Wet Wt - Dry Wt) X pb]/DrY Wt)
Clsw = Chloride in soil water (mg/i)
Cle = Chloride in the extract (ppm)
Wtr added = Amount of dionized water added to sample (g)
Dry Wt = Weight of oven dried sample (g)
Wet Wt = Weight of sample and water (g)
= Bulk density (glcu. cm)
CUMULATIVE CHLORIDE (CC) AT A GIVEN DEPTH
CC = (Clsw X L)
CC = Cumulative chloride (g/sq. m.)L = Sample interval length (in)Clsw = Chloride in soil water (g/cu. in.)
VOLUMETRIC WATER CONTENT (Vwc)
Vwc = [(Wet Wt. - Dry Wt.) X b] / Dry Wt.
25
APPENDIX 2
VALUES USED IN SENSITIVITY ANALYSIS
Bulk Density Cisw(g/cu. cm) (mg/i)
Cip Precipitation Clew(mg/i) (mm/year) (mg/i)
.19 100 475.6 .0399
.19 100 402.4 .0470
.19 100 348.8 .0530
.19 100 327.0 .0580
.55 100 475.6 .1158
.55 100 402.4 .1367
.55 100 348.8 .1577
.55 100 327.0 .1682
.55 350 475.6 .4048
.55 350 402.4 .4784
.55 350 348.8 .5519
.55 350 327.0 .5887
Cip Precipitation Cumulative chloride Age(g/cu. m) (rn/year) (g/sq. rn.) (years)
.19 0.10 1864 98105
.19 0.10 1300 68421
.19 0.10 1042 54842
.55 0.10 1864 33891
.55 0.10 1300 23636
.55 0.10 1042 18945
.55 0.35 1864 9683
.55 0.35 1300 6753
.55 0.35 1042 5413
26
Recharge rates(mm/year)
1.1 475. 6 Chloride values calculated1.3 402 .4 using chloride in extract1.5 348.8 = 20 ppm.1.6 327.0
CHAPTER 2
PALEOCLIMATIC IMPLICATIONS OF CHLORIDE PROFILE SHAPES:APPLICATIONS FOR LONG-TERM GROUNDWATER PROTECTION
WHISKY FLAT, NEVADA
To be submitted to: Quaternary Research
TABLE OF CONTENTS
Page
ABSTRACT 1
INTRODUCTION 2
REGIONAL SETTING 3
METHODS 7
GEOMORPHIC SURFACES 7
WATER-TABLE ELEVATIONS 8
DRILL-SITE SELECTION 11
DRILLING AND LAB PROCEDURES 12
CHLORIDE MASS BALANCE METHOD 12
RESULTS 13
DISCUSSION 17
REGIONAL CONTROLS ON CHLORIDE PROFILE SHAPES 17
Modern Root and Percolation Depths 18
Past Root and Percolation Depths 21
Modern and Paleo Water Tables 25
LOCAL CONTROLS ON CHLORIDE PROFILE SHAPES 29
Influent Stream Flow 29
Aggradation and Erosion 29
GROUNDWATER RECHARGE RATES AND GEOMORPHIC-SURFACE AGES 31
CONCLUSIONS 32
REFERENCES 36
APPENDICES 41
ABSTRACT
A chloride mass-balance approach was used to determine the long-term
groundwater recharge rates and geomorphic-surface stability at Whisky Flat, Nevada.
The recharge estimates were based on data from the WF 5 profile because the other
profiles showed evidence of subsurface leaching. Rates ranged from 0.04-0.8 mm/yr.
0.8 mm/yr is interpreted as the maximum recharge rate that occurred during the
Pleistocene when effective precipitation was greater. Under the more arid modern
climate, recharge is probably much less. WF 7's profile indicates that deep
percolation depths may currently be limited to the upper 5 m.
The upper zone of WF 1 has fluctuating chloride values which represent
aggradational pulses, while the upper zone of WF 5 records a local erosional event
that took place 130-1780 years BP. The upper zones of profiles WF 2, 3, and 4
correspond to stable geomorphic surfaces, and are estimated to be 5500-125,000
years old. The age range is great because long-term precipitation and chloride
input averages cannot be tightly constrained given the available paleoclimatic
information. The estimates do, however, suggest that the calculated recharge rates
are representative of at least the last 5,000 years.
Modern evapotranspiratlon depths appear to be confined to the upper 3 m. The
high chloride concentration in the upper 7.7 ni of profile WF 2 is therefore
interpreted as recording the maximum root depth during the Pleistocene, while the
intermediate concentrations from 7.7 to 9.6 m record the maximum percolation depth.
The difference between these two depths probably reflects the lag between the
increase In effective precipitation and the subsequent change in vegetation type
and rooting depths which would capture the water and concentrate the chloride at
shallower depths. The upper 9.6 m thus defines the long-term, hydrologically
active zone.
1
INTRODUCTION
Evidence for climatic change is well-documented in the paleoclimatic record
for the Southwest. However, the impact of long-term climatic change on recharge
rates and percolation depths has been addressed only in a qualitative way. This is
no longer enough if the quality of groundwater Is to be maintained. Improper
disposal of toxic wastes and an incomplete understanding of the long and short-term
hydrologic characteristics and geomorphic stability of disposal sites has resulted
In serious contamination of numerous groundwater systems. Clean-up Is expensive,
time-consuming, and often delayed for political and economic reasons.
The search for disposal sites, where groundwater contamination is likely to be
minimal, has led to arid and semi-arid alluvial basins where mean annual
precipitation is low, evaporation high, and subsurface layers frequently impede
percolation. Under these conditions, groundwater recharge through the sediments is
presumed to be very small (WInograd, 1981; Roseboom, 1983). However, long-term,
cost-effective groundwater protection requires tools that indicate the hydrologic
and geomorphic response of a potential disposal site to climatic change. Chloride
mass balance appears to be one way to address this issue quantitatively.
The mass-balance approach is based on the extreme solubility of chloride.
Chloride's affinity for water provides a direct link between the amount of water
ioving through a soil profile and the amount of residual chloride at a given depth,
and provides an important clue to the interaction between surface conditions and
subsurface vadose-zone flow over thousands of years. While the theoretical
assumptions used in the recharge (salt-balance) and surface age (salt-age)
equations are not valid under semi-arid and arid conditions, or over the long time
spans involved, the assignment of ranges in chloride and precipitation input values
accounts for climatic variability (Fouty, 1989).
2
Variation in chloride concentration with depth is the basis for the mass-
balance approach. The chloride profile generally has an upper and lower zone
(Figure 1). The lower portion provides information on recharge and leaching
mechanisms, while the upper portion reveals information on percolation and rooting
depths, and geomorphic-surface age and stability.
This paper evaluates the types of long-term geomorphic and hydrologic
information provided by the profiles from Whisky Flat, a small basin in western
Nevada (Figure 2). This area was chosen because the availability of paleodlimatic
Information permitted reconstruction of qualitative changes in effective precipita-
tion. These changes could then be compared with recharge rates and infiltration
depths determined from the chloride method. The predominantly granitic alluvial
provenance also minimized the amount of soluble chloride contributed from the
surrounding country rock, while the small basin width (6.5 km) would hopefully
decrease the importance of a climatic gradient across it. The final and most
critical factor was the varying depth to water at Whisky Flat which permitted
testing the hypothesis that fluctuations In the modern or paleo water table could
significantly impact chloride concentration at depth and lead to an overestimation
of recharge rates through the sediments.
REGIONAL SETTING
Whisky Flat, a typical basin and range depression, is located approximately 20
km south of Hawthorne and Walker Lake. The basin (Figure 3) is bordered on the
west by the Cretaceous granodiorite of the Wassuk Range and the Tertiary volcanics
of the Anchorite Hills. It is bordered on the east by the Cretaceous-Jurassic
blotite granite, and Cretaceous granodiorite of the Excelsior Mountains and the
3
5
20-
25
Figure 1. Generalized chloride profile showing major zones of accumulation.
Chloride concentration (mg/I)
4
Upper zone
Lower zone
0 3000 6000 9000
0-
32
I22 120I I I
CALIFORNIA
SIERRANEVEDA
£ STUDY SITES
IT11IGREAI BASIN DESERT
5
n
112
MOJAVE DESERT
Figure 2. Location of study area (modified from Spaulding et al., 1983).
-300KM
I I
TRTIARY-QlJATERNARY TRIASSC-JURASSlCVOLCANICS SEDIMENTS,SOME VOLCANIC
Figure 3. Generalized geology of area surrounding Whisky Flat (modifiedfrom Ross, 1961; Stewart et al., 1981).
6
Tertiary volcanics of the Garfield Hills. Minor amounts of Triassic and Jurassic
sediments and volcanics occur in both the Excelsior Mountains and Garfield Hills
(Ross, 1961; Stewart et al., 1981). BasIn fill consists of poorly stratified,
gravelly, silty sands, with some clayey sands and sandy clays. Four small playas
occur, two along the eastern side of the basin, and two within the Wassuk Range
(Stewart et. aL, 1981).
The elevation of the basin floor averages 1798 m and is about 500 in higher
than the weather station at Hawthorne, where mean annual precipitation is 120
mm/year. Eighty-five percent of the precipitation at Hawthorne occurs from
November to April. A lapse rate of 50 mm increase in precipitation/100 m rise In
elevation (Barry, 1973) resulted In an estimated average precipitation of 350
mm/year for Whisky Flat. This is probably too high a modern rate (Walters
Engineering., Nevada, writ. comm., 1988), and is taken as an upper maximum only.
Mean annual runoff averages 25 mm at Whisky Flat (Nevada State Engineer. 1972).
Mean monthly temperatures at Hawthorne range from 1.6°C in January to 25°C in July.
Prevailing winds are northwest-southeast (National Oceanic and Atmospheric
Administration, 1971). The water table surfaces at Whisky Springs at the northern
end of the basin, but Increases to more than 85 in deep at Its southern end. The
spring discharges about 0.1 Cu. rn/day (25 gpd) (Nevada Water Resources
InvestIgation, 1976). Sagebrush is the dominant vegetation in the basin,
while pinyon-juniper forests dominate the mountain slopes.
METHODS
GEOMORPHIC SURFACES
Extensive geomorphic mapping during the summer of 1986 established relative
7
surface ages and provided the basis for later drill-site selection. Geomorphic
surfaces were initially separated out based on degree and type of dissection,
color, stratigraphic position and aerial extent as evident from 1:24,000 color
aerial photos. Classifications were field checked by digging soil pits and
evaluating soil characteristics using the Harden Index (Harden, 1982; Appendix 1)
and degree of hard-pan development (Appendix 2). This additional factor was added
in to the Index value using a semi-quantitative test designed to measure aggregate
strength. Relative surface age estimates compare with those of Stewart et al.
(1981).
Pleistocene surfaces cover the largest area and extend down to the basin
center. Holocene deposits are concentrated along the mountain fronts, while active
surfaces are confined primarily to stream channels and to small sheet-like deposits
(Figure 4). Volcanic ash was found in several drill cores and provided some age
control.
WATER-TABLE ELEVATIONS
Nine water-level readings from 1958 exist for Whisky Flat. The water wells
were approximately located based on their legal descriptions (Nevada Department of
Water Resources), and a topographic profile constructed through the well points to
determine the relationship between land-surface and water-table elevations (Figure
5). Defining this relationship was necessary because the water wells were
clustered in the basin center while the drill sites would be located up on the
alluvial fans. The profile revealed two slopes, both nearly flat. A-A' averages
1.5 rn/km and B-B' average 6 rn/km.
8
auun4iE
Vd814AWTHORNE -I 20 KM.
V
Sc
ACTIVE-RECENTLY ACTIVE
LATE NOLOCEME
Mm-EARLY HOLOCENE
PLEISTOCENE
RECENTLY STRIPPED
UNkNOWN (SOIL INOEN VALUES ANDTOP SUGGEST DIPPERENT AGES)
Figure 4. Surficial geology of Whisky Flat and location of soil pits anddrill sites.
9
SANITE NO 5011.3 DATA
VOLCANIC S
'4 SOIL PIT
URIED SEDROCK RIDGE
DRILL HOL1
EPHEMERAL STREAM
1780-
1740-
1700-ILl -
1660-
1620
1)
io
eRAsd ITE
VOLCANIC
0 DRILL SITEI5BWAT5p WELL WITH
DEPTH TO WAER Cm) ANDC YEARN -
TAKEN.
, IURIED IDROCK RIDGE/ JE!ICD WHERE UNCER-TA IN.
dsr'coNTouR LINE INMETERS
= Estimated water surface
111111 111111Whisky Springs
2 4 6 8 10 12 14 16
Distance (km)
Figure 5. Land-surface and water-surface elevation relationship.(a) Location of wells used in water-surface analysis, and cross-section locations. (b) Topographic profile showing land-surfaceand water-surface elevations.
1860-
/ LINE OF TRANSECT.
A - N1820 -
B - B'
DRILL-SITE SELECTION
Once the geomorphic surfaces and a tentative relationship between land-
surface and water-table elevations were defined, seven drill sites were selected to
look for signatures in the chloride profile that might indicated subsurface flow.
Hole WF 6 was not used because it was a Pleistocene surface covered by a thin
veneer of Holocene sediments. Data for the six holes used are given in Table 1.
Four drill sites were situated on Pleistocene surfaces at varying elevations
above the estimated water table. As chloride concentration and profile shape
change through time, this selection limited the complications inherent in
interpreting profiles from different aged surfaces. The fifth site was located on
a recently active surface, and the seventh in an ephemeral stream in the center of
the basin (Figure 4). Sediment lithologies in all cores were similar, though the
percentage of gravel, sand, silt and clay varied with distance from the mountain
front and depositional environment. Differences In grain size were noted during
drilling and verified through sieve analysis (Appendix 3).
11
Table 1. Summary of drill hole characteristics.
Total depth
Interval
Sample
Surf ace
levaticn
8otto.
elevation
Drill hole Setting Location Geology Alluvial provenance (a) (a) (a) (a)
I Recently active
alluvial surface
Western side Alluvium Cretaceous granite 15.09 0.09-15.09 1713 1697.9
WE2 Pleistocene
alluvial fan
Western side Alluvium Cretacecus granite 20.10 0.0-20.1 1728 1707.3
WF3 Pleistocene
alluvial fan
Western side Alluvium Cr.taceous granite 11.30 0.0-11.3 1707 1695.7
WF4 Pleistocene
alluvial fan
Western side Alluvium Cretaceous granite 5.80 0.0-5.8 1823 1817.2
WP5 Pleistocene (?)
alluvial far
Eastern side Alluvium Crutacecus granit. 18.80 0.0-18.8 1823 l80i.2
WP7 Ephem.r,l strea. Baafn center Alluvium Cretacecus granite/ 5.80 0.0-5.8 1780 1774.2
Tetlary volcanici
DRILLING AND LAB PROCEDURES
Whisky Flat cores were drilled dry, using a continuous-sampling, hollow-
stemmed auger. Samples were collected at varying intervals with frequent sampling
in the upper 4.5 in to insure proper definition of the chloride peak. Core recovery
averaged 80 % for the 0.75 in cores and 53 % for the 1.5 m cores. Each day's
samples were temporarily stored in the field and then weighed at night.
Lab procedures for extracting and measuring the chloride content of the soil
samples were as described by Stone (1984a, b; McGurk and Stone, 1985). No
volumetric samples were collected at Whisky Flat, so a bulk density of 1.5 g/cc was
assumed. Equations used to calculate chloride concentration and volumetric water
content are listed in Appendix 4.
CHLORIDE MASS-BALANCE METHOD
Groundwater recharge rates and minimum geomorphic-surface ages were calculated
using the chloride mass-balance method. This method relies on the salt-balance and
the salt-age equations. Prior work used as many as eight assumptions (Allison and
Hughes, 1978; Stone, 1984a, 1986, Gifford, 1985; Allison et al., 1985), but a close
examination revealed that very few were valid in arid and semi-arid regions, in
unsaturated sediments, or over thousands of years (Fouty, 1989). Therefore, this
paper used only the assumption that precipitation is the sole source of recharge
through the alluvial sediments.
The salt-balance equation is used to determine groundwater-recharge rates
R = (P x Clp)/Clsw (Allison and Hughes, 1978), where (1)
R = recharge rate (mm/year), P = precipitation (mm/year), Cit = total annual
chloride Input (mg/L), Clsw = average chloride concentration in the soil below the
root zone (ing/L).
12
Chloride concentration in the soil samples collected in the field were
determined by lab analysis. An average Clsw was determined for the lower zone from
plots of chloride versus depth. The variation in chloride and precipitation inputs
through time were accounted for by assigning a range In values that appeared
appropriate for the study site. Modern values obtained from the literature were
considered the minimum range for each parameter.
The salt-age equation gives the relationship between time and the amount of
chloride accumulated in the soil by evapotranspiratiOn (Bouwer, 1980; Stone, 1984a;
Matthias et a]., 1986).
A CCs/(Clt x P), where (2)
A = age (years), CCs = cumulative chloride in the soil from the surface to a given
depth (g/sq. m), Clt = total chloride input (g/cu. m), P = precipitation (rn/year).
The amount of chloride in the evapotranspiratlon zone can be used to calculate
the timing of certain erosional events (this paper), and minimum geomorphic-
surface ages (Allison et aL, 1985). However, the age calculation can only be done
for stable, nonaggrading surfaces (Fouty, 1989). The narrower the precipitation
and chloride range, the better the age estimate. Previously, the amount of
chloride accumulated above a given depth had been equated with the age of the water
at that depth (Stone, 1984 a,b; Phillip and Stone, 1985). However, this
relationship requires that the assumption of piston flow be valid, which It is not
(Starr et al., 1918, 1986; Allison and Hughes, 1983; Yeh et al., 1985; Stone, 1985;
McCord and Stephens, 1987).
RESULTS
Moisture and chloride values obtained are listed in Appendix 5, cumulative
13
chloride/cumulative water data are given In Appendix 6, and moisture and chloride
profiles for each core are found in Appendix 7. The chloride profiles were
compared for similarities and differences which would indicate the types of
geomorphic and hydrologic influences acting on them.
All chloride profiles, except that for WF 7, show a zone of high chloride
concentration near the surface, which decreases with depth (Figure 6). Beyond
shape similarity, the location, thickness and concentrations of the chloride peaks
vary significantly. In WF 7, peak values are displaced downward, while In WF 5,
the evapotranspiration (ET) chloride peak occurs at 1.7 in, Is narrow and
characterized by low concentrations. In contrast, ET chloride concentrations in WF
1, 2, 3, and 4 exceed 4000 mg/L and have respective zones 7.5, 7.7, 3.9, and 5.7 in
thick. 5.7 in represents only a minimum ET zone thickness for driU hole WF 4
because boulders prevented deeper drilling. Values in the upper portion of WF I
fluctuate considerably, but hold steady In WF 2, 3, and 4. ChlorIde concentrations
In WF 1, 2, and 3 decreases rapidly to < 100 mg/L, but at different subsurface
elevations. Values remain above 200 mg/L for WF 5. Moisture content (FIgure 7)
averages 4-8% for WF 1, 2, 3, 4, and 5, and 11% for WF 7 (ephemeral stream).
Volcanic ashes found In WF 1 (3.5 in), WF 2 (7.3 in), and in WF 3 (7.7 m) were
sent to J. 0. Davis at the Desert Research Institute in Reno, Nevada for
identification. The ash in WF 1 fits well within the petrographic and chemical
range of post-1800 year BP Mono Crater ashes. WF 2 is similar to several ashes
seen by Davis (writ. comm., 1987), but In the absence of associated radiocarbon-
dateable material, the best upper age limit for these ashes appears to be 75,000
yrs BP. Using the apparent tendency of Mono Crater ash to become richer In Fe and
poorer In Ca through time, Davis narrowed the likely age range for the WF 2 ash to
47,000 + 7,000 years BR The value assigned should be viewed with caution because
14
WF
4P
leis
toce
ne S
urfa
ceC
hlor
ide
conc
entr
atio
n (m
g/I)
050
0010
000
E -a -c 4., a- U a
WF
5P
leis
toce
ne S
urfo
ceC
hlor
ide
conc
entr
atio
n (m
g/I)
Figure 6.
Chloride versus depth profiles for Whisky Flat drill sites.
E 5.-
-c a, a. 0 a
WF
7E
phem
eral
Str
eam
Chl
orid
e co
ncen
trat
ion
(mg/
I)0
5000
1000
00
5000
1000
0
I0-
0 5-
10-
10-
-c-C
-J a. 0 a15
-
20-
20-
25-
25-
WF
1W
F2
WF
3R
ecen
tly A
ctiv
e S
urfa
ceP
leis
toce
ne S
urfa
ceP
leis
toce
ne S
urfa
ceC
hlor
ide
conc
entr
atio
n (m
g/I)
Chl
orid
e co
ncen
trat
ion
(mg/
I)C
hlor
ide
conc
entr
atio
n (m
g/I)
050
0010
000
050
0010
000
050
0010
000
-c +1 a-
WF
1R
ecen
tly A
ctiv
e S
urfa
ceM
oist
ure
cont
ent (
cu. r
n/cu
. m)
0.00
0.10
0.20
WF
4P
leis
toce
ne S
urfa
ceM
oist
ure
cont
ent (
cu. r
n/cu
. m)
0.00
0.10
0.20
0
0 E -C a- Q) 0
WF
2P
leis
toce
ne S
urfa
ceM
oist
ure
cont
ent (
cu. r
n/cu
. m)
0.00
0.10
0.20
0I
I
5.E
*1
-c15
-
20-
25
WF
5P
leis
toce
ne S
urfa
ceM
oist
ure
cont
ent (
cu. r
n/cu
. m)
0.00
0.10
0.20
WF
3P
leis
toce
ne S
urfa
ceM
oist
ure
cont
ent (
cu. r
n/cu
. m)
0.00
0.10
0.20
0 10
-c'5 20
Figure 7.
Moisture content versus depth profiles
or Whisky Flat drill
sites.
25
WF
7E
phem
erol
Str
eam
Moi
stur
e co
nten
t (cu
. rn/
cu. m
)0.
000.
100.
20
0
4,
5.
E10
-C a.'5
-0
20-
25
E10
-c a-15 20 25
of the large uncertainty In assuming a constant rate of change in Fe and Ca with
time (Davis, writ. comm., 1987). The ash in WF 3 was not analyzed, but is believed
to be the same as the WF 2 ash, based on its similar depth below land surface.
Selected core samples were sieved to determine if grain size might affect
chloride and water distribution within the profile. Two sieve analyses were done
to determine the relationship between moisture content and grain size, and soil
texture and grain size. One analysis included gravel, the other did not. An
Increase in silt and clay correlated roughly with an increase in moisture content
and accounted for some of the variability seen In the moisture profiles. Sand and
gravel percentages were high in all samples but varied as a function of distance
from the mountain front and depositional environment (AppendIx 3).
DISCUSSION
Controlling influences on chloride profile shapes fall into two categories:
those that are regional in extent, and those that are local. Water-table
fluctuations, and changes in root-penetration depths and percolation depths due to
climatic changes are regional controls. Buried stream channels, local influent-
stream flow, downslope movement along impermeable zones, aggradation/ erosion, and
groundwater recharge rates are local controls. The upper portion of a chloride
profile records changes In percolation and rooting depths and the lower portion
reflects subsurface leaching mechanisms and recharge rates.
REGIONAL CONTROLS ON CHLORIDE PROFILE ShAPES
Beatty, Whisky Flat, sites studied in New Mexico (Stone, 1984a, 1986), and at
the Nevada Test Site (Glfford, 1985) show zones of high chloride concentrations 4-
17
7+ m thick in the upper portions of their profiles. Modern infiltration and root
penetration depths were evaluated at Whisky Flat to determine if the thick upper
zone was indicative of modern conditions or recorded an earlier, wetter time. This
is a complex task, as a profile's evapotranspiration (ET) zone is a composite of
modern and paleoclimatic and vegetative conditions. Separation of the components
relied heavily on a paleoclimatic reconstruction, a summary of referenced root-
penetration depths in the western United States (Foxx et al., 1984), 36C1 depths
(Trotman, 1983; Gifford, 1985), and an ET-peak depth of an old, but recently
stripped surface at Whisky Flat.
Modern Root and Percolation Depths
Transpiration and evaporation control recharge rates and percolation depths.
The influence of evaporation in semi-arid and arid areas, where water tables are
deep, appears to be confined to the upper 3 m (Enfield et al., 1973; Bouwer, 1978;
Hillel, 1982), while the influence of transpiration on the depth of percolation
varies significantly as a function of climate, vegetation type, root density and
depth, and availability of water.
The rooting depth of the current vegetation at Whisky Flat was estimated using
the summary by Foxx et al. (1984) of environmental and biological factors
controlling root depth. This summary used a data base compiled in 1981-82 of
rooting depths of native plants in the United States and contained 1034 citations
and approximately 12,000 data elements. Foxx et al. (1984) looked at seven
controlling factors, but this study only used soil type, regional evaporation
potential, and plant type to determine if the roots of the current vegetation at
Whisky Flat were likely to penetrate depths > 3.7 m. Soil type (cf. Table 2) was
felt to be an independent variable, and therefore fairly constant over the last
18
30,000 years. Evaporative region provided an indirect link between modern climate
and vegetation.
Table 2 lists cumulative root-depth frequencies for five soil types. The soil
types at Whisky Flat are mainly sand and sandy barns (Appendix 3). This suggests
that most p1ants in the area should root between 2.7 and 3.7 m. The shrub data has
an average rooting depth of 3.5 in, with a median depth of 1.95 in. Big sagebrush
accounted for 9 of the 87 shrub references, and rooted to approximately 2 in in
alluvial soils (Foxx and Tierney, 1986). Regional evaporation potential indicates
that about 90% of all specimens in Region 2 (Whisky Flat area) should root to 3.7 in
or less (Foxx et al., 1984). The 10 % found at depths > 4.6 in were usually trees
and shrubs rooting through cracks In clay soils and fractured rock In mine tunnels,
or herbaceous perennials, trees, and shrubs tapping water at depth.
Table 2. Cumulative root depth frequencies (%) for fivesoil types at selected depths (Foxx et aL, 1984).
Root depth
Soil type 91 cm 183 cm 274 cm 336 cm 457 cm
Adobe clay 66 89 99 99 9
Loam 54 95 99 100
Clay loam 48 83 94 99 99
Sand 44 76 90 98 99
Silt 31 64 80 83 93
A second line of evidence for the modern ET depth was provided by chlorine-36
(36Cl) data from the Nevada Test Site and Socorro, New Mexico, and a shallow
chloride peak at Whisky Flat. The 36C1 pulse was generated during the 1950's and
19
1960's thermonuclear bomb testing and has since been used as an environmental
tracer and a tool in dating groundwater (Trotman, 1983; Phillips and Stone, 1985;
Gifford, 1985; Bentley et al., 1986). Climate over the last 40 years has varied,
but the variations tend to be short-term, high-frequency events. This is in
contrast to the long-term, low-frequency wetting and drying event which occurred in
the western Great Basin during the last 30,000 years. Therefore, climate over the
last 40 years is assumed to have been relatively constant, as compared to the last
30,000 years, and the depth of the 36C1 pulse is taken to indicate present ET
depths.
Trotman saw a distinctive 36C1 pulse at 1.13 m with chloride rates constant
below 2 m near Socorro, New Mexico. Mean annual precipitation at Socorro is 220
am/year and mean monthly temperatures range from 2-26 °C. Gifford (1985) found the
maximum concentration of 36C1 at 0.5 m at the Nevada Test Site, 90 km south of
Beatty, where mean annual precipitation is less than 113 mm/year, or approximately
half that at Socorro. Mean monthly temperatures at Beatty range from 5°C to 27°C.
Shallow percolation depths in arid regions is supported by neutron log readings
taken at the Beatty site from January through April 1987 (Fischer, writ. comm.,
1987) and an earlier study by Nichols (1986). The neutron logs showed no change in
the soil-water contents despite the occurrence of three closely spaced storm
events: February 23-25 (6.1 mm), March 5-7 (9.1 mm), and March 15 (23 mm).
There are no 36C1 data for Whisky Flat, but characteristics of the WF 5
profile provide an important clue to modern ET depth. The WF 5 surface was mapped
as Pleistocene, yet the depth and thickness of its high chloride peak differs
significantly from WF 2, also on a Pleistocene surface. WF 5's peak is narrow (0.6
a thick versus 7-9 m thick) and confined to the upper 1.7 m of the profile (Figure
6). It appears that this surface has been locally stripped, probably during the
20
Incision of the adjacent deep wash. This 1.1-1.7 in zone is interpreted as
representing the current ET depth in this basin. This depth fits within the modern
depth/climatic pattern suggested by the 36C1 data. Clearly neither the root
analyses nor the suggested ET depth estimates can account for the 7-9 in chloride
zone seen in WF 2. If modern conditions cannot account for a thick, high chloride
concentration zone, then perhaps past percolation and root-penetration depths are
being recorded in the chloride profile.
Past Root and Percolation Depths
Reconstruction of Southwest and Great Basin Pleistocene climate indicates
changes in effective precipitation (precipitation - evaporation) over the past
18,000-21,000 years. This change was accompanied by changes in basin vegetation
types (Spaulding et aL, 1983). The absolute magnitudes of the temperature and
precipitation change is still debated. However, what is important for this study
Is the net effect of those changes on recharge rates, and rooting and percolation
depths.
Available climatic data for south-central Nevada is plotted qualitatively in
Figure 8a and the location of references' sites shown in Figure 8b. Data for the
region around Whisky Flat are scarce so information from southern Nevada was
Included. Mifflin and Wheat (1979) data are not included on the diagram because it
was impossible to equate their relative ages to an absolute time scale.
Figure 8a shows unanimous agreement regarding an increase In effective
precipitation in the Southwest from 21,000-15,000 years 81'. Changes, however.
appear to be due to lower temperatures throughout the western Great Basin province,
rather than increased precipitation falling directly on the basin floor (Mifflin
21
0
4-0
z0
4-a_I-. 0->uLtO
'az
4-
ur -
3O-E
SOUfl4-CENTRAL NEVADA
20
YEARS BEFORE PRESENT Q)
Figure 8a. Qualitative summary of relative changes in Precipitation -Evaporation (P-E) estimated from 30,000 years ago to present.(+) indicates values greater than present; (-) indicates valuesless than present; and (0) indicates present values. Source is
noted in right corner, data set in the upper left corner.
22
EMORPI,IC .RCESSOIL AR4CTERISIICS, 8LAKE LEVEL----- WELLS,.t,L987
SEDIMENIOLDOICAL0F4ARAcIERISTICS aMOLLLSCS
t
O.JADE,P985
PACK RAT MIDOENS
SPAULON..foL 1984
PACK RAT MIODENS
SPAULPINA 8 AUMLIC4 1986
D0NRENWENO984
PACK RAT MIDOENS
VAN OEVENOER 1977
CX RAT MIDOENS I
THOMPSON B MEAD 982
PACK RAT MIDOENSPOLLEN
SPAULDING,I$SI., 1983
GLO. LIMATICM0DELS(3O-$O'N II-.,LAKE LEVELS
DAVIES . 1982
LAKE LEVELS
SENSON 8 TI1OMPS0NI987
PACK RAT MIOCENS
DAVIS & SELLERS IN PRESS
GLQ8AL CLIMAI1CMOPELS (3O-6ON)
XUTZSACH a 3IJCTTER. 986
PACK RAT MIOOENS
T 44 OM PS ON 1984
-36°N
-37°N
SIERRANEVADA
o ioo 200 300KILOMETERS
MONOLAKE
OWENSLAKE
SEARLESLAKE
WIN NEMIJ CCALAKE
LAKELANON TAN
WALKER GATECLIFFLAKE £SI.4ELTER
£WHISKY FLAT
ELEANA)CRANGE
\BE A TTY
MANLYLAKE
.
rLAKE
[LAS VEGAS'-'(TULE SPRINGS)\\
\\LAKEUMOHAV
QD .
070 N-j-
-t-
360M4
12-8 KYR AREAS OF£ STUDY SITE 0 DESERT SCRUB
12-B KYR AREAS OFN000LAND
Figure 8b. Location of areas for which paleoclimatic information isavailable (modified from Smith and Street-Perrott, 1983).
23
and Wheat, 1979; Dohrenwend, 1984; Benson and Thompson, 1987). Mifflin and Wheat
(1979) concluded that the full-glacial climate in south-central and southern
Nevadan basins was actually more arid than present. This is supported by recent
sedimentological work by Quade (1986) in the Las Vegas Valley. The paleoecology of
the Southwest suggests, at most, only a small Increase in average annual
precipitation (Spaulding et al., 1983).
15,000-8,000 yrs BP appears to be a period of transition. Effective
precipitation continues to be greater than present until about 8,000 yrs BP, but
the trend is towards drier conditions (Figure 8a). The only exception to this is
Kutzbach and Guetters (1986) climatic analysis for the northern- middle latitudes
(30-60°N). This difference is attributed to their use of a global scale compared
to the other, more local analyses (Spattlthng and Graumlich, 1986). Information for
the last 10,000 years is scarce and somewhat conflicting. Modern conditions,
however, appear to have been achieved about 8,000 BP.
The modern percolation and rootIng-depth estimate of 1.7 in is too shallow to
explain the thick chloride zones seen in several of the profiles. Instead, these
zones appear to record the wetter Pleistocene conditions, and were preserved in the
chloride profile because of a climatic trend towards aridity. The thickest high
chloride zone is 9.6 m and occurs in WF 2. Here chloride concentrations are
greater than 3000 mg/L in the upper 7.7 m, decreasing quickly to less than 2000
mg/L between 7.7 m and 8.7 in. This relatively abrupt decrease is perhaps recording
the lag between the increase in available moisture and the subsequent change in
vegetation type and density. The base of this second, lower zone of high chloride
at 9.6 m, is interpreted as defining the long-term, active percolation zone at
Whisky Flat.
24
Modern and Paleo Water Tables
Pleistocene water-table rises have been documented for closed basins in the
Southwest (Mifflin and Wheat, 1979; Smith and Street-Perrott, 1983; Quade, 1986).
However, only rises which intersected the surface left surficial evidence of the
event. One method for documenting areas where subsurface rises occurred may be the
chloride mass-balance method. Evidence for a subsurface rise would be an abrupt
decrease in chloride concentrations at depth in a chloride profile, with the depth
to the low chloride zone varying as a function of land-surface elevation. This
variation with land surface indicates that concentrations are not simply decreasing
to background levels.
This type of a chloride pattern was sought in profiles WF 1, 2, and 3. These
profiles are closest to the basin center and had shallow water tables prior to
pumping by Sweetwater Ranch. The 1958 water levels for wells near WF 1 and 3 are
similar (Figure 5), and the water table is assumed to have been relatively flat
between these two points. Groundwater chemistry reports list chloride concentra-
tions in the basin at 18 mg/L (Nevada Division of Health, 1983). An evaluation of
all the chloride profiles in the basin suggests that concentrations at depth, less
than 100 mg/L, may record subsurface leaching.
Whisky Flat is a closed basin and is separated from the Walker Lake aquifer to
the north by a buried bedrock ridge (Nevada Water Resources Institute, 1976). A
spring occurs in the vicinity of the ridge, and a surficial channel connects the
two areas. The channel is bounded by bedrock on the east and a Pleistocene
alluvial surface on the west where it exits the basin (Figure 4). Three scenarios
are possible for leaching chloride at depth: (1) a steepened groundwater gradient
between the mountain and basin, (2) blockage of the channel at the northern end
resulting in a basin-wide, water-table rise, or (3) both.
25
The present channel prevents the formation of a lake should the modern water
table rise. However, if the Pleistocene surface were to extend across the narrow
channel (channel floor at 1658 m), it would create a dam 12-24 m high or a land
surface at 1670-1682 in (Figure 9). A basin-wide, water-table rise to 1670-1682 m
would not affect any of the profiles, unless it was accompanied by a steepened
groundwater gradient between the mountain front and basin. Shorelines are absent,
but the topographic contours at 1670m (5480 ft) and 1682 m (5520 ft) would close if
the surface extended across the constriction. This suggests the possible existence
of a small temporary lake which may have overtopped the dam and been responsible
for the incision of the Pleistocene surface.
The other possibility is that the groundwater gradient between the mountain
front and the basin center was higher and/or steeper in the past when recharge
along the mountain front was greater. Water-surface-elevation maps often show the
water table following land-surface topography, but at a gentler gradient (Davidson,
1973). Figure 10 shows such a relationship, with depth to the low chloride zone
varying as a function of land-surface elevation. None of the drill holes
intersected the modern water table, but this may be an artifact of water-table
decline due to pumping by. Sweetwater Ranch. Therefore, the slope In Figure 10
could represent either the modern, prepumping water table or an older water table.
A change in the gradient would affect all three drill holes even If the channel was
not blocked.
It is assumed that the lower portion of WF 1 is Pleistocene. However, the
post-1600 year old Mono Crater ash found at 3.5 in, and the fluctuations in chloride
values in the upper 7.4 in indicate that at least the upper 3.5 m is late Holocene.
Whether the lower profile is Pleistocene Is unclear, and the slope in Figure 10 may
be coincidental.
26
PLEISTOCENE SURFACES
GRANITE
VOLCANICS
Li.I
1800-
1750 -
(23)c
27
*
DRILL SITES
EPHEMERAL STREAM
WELL W/ DEPTH(2) LISTED IN METERS
1682 m1670 m
1650I I I I
0.0 0.5 1.0 1.5 2.0
D Distance (km) D'
Figure 9. (a) Location of cross-section C_C! (Figure 10) and D_D!.
(b) Topographic profile across the channel with continuationof the Pleistocene surface noted (D-D')
1780-
1760 - less than 100 mg/iE
1740-o WF2
..
a1720 WF1iii WF3
1700 -
16800 1 2 3 4
Distance (km)
Figure 10. Relationship between elevations of land surface and the top ofthe low chloride zone. The profile is taken through WF 2, 3, andone water well (Figure 9a, C-C'). WF 1 is projected onto theprofile based on its elevation.
28
A Chloride concentration
LOCAL CONTROLS ON CHLORIDE PROFILES
Influent-Stream Flow
Influent-stream flow can have a significant impact on subsurface water
contents (Wilson and DeCook,1968; Wilson, 1971). Because surface and subsurface
sediment characteristics determine direction and velocity of water movement in the
vadose zone (Wilson and DeCook, 1968; Hill and Parlange, 1972; Bouwer, 1980;
Hillel, 1982; Yeh et aL, 1985), drillers logs, moisture-depth profiles, field
descriptions of samples, and grain-size analyses were examined for information on
subsurface stratigraphy. Whisky Flat alluvium is primarily sand and gravel, with
some thin Interbedded clayey sands and sandy clays. Strong vertical gradients
would be expected on the alluvial fans if saturated flow conditions existed. The
basin-center sediments, however, are fine-grained (Stewart et al., 1981; this
study) and probably impede downward percolation during the spring floods.
WF 3 is the only hole where basin-flood flow might be leaching the lower part
of the profile, provided that the basin sediments permit infiltration, or that
flood waters rise high enough to infiltrate through the fan sediments. The absence
of water-level readings during flooding precludes determining rates and magnitudes
of infiltration, but this may explain why the ET zone for WF 3 is only 39 m thick
versus the 7.7 m seen in WF 2. The elevations of WF 1 and 2 above the basin center
and the inclination of their beds towards the center decreases the likelihood of
chloride leaching at depth due to subsurface-lateral flow of basin-flood waters.
If influent-stream flow is leaching chloride from WF 1 at depth, flow is from the
adjacent, 12 m deep side channel.
Aggradation and Erosion
A steady-state profile is absent in WF 1 with chloride values fluctuating
29
considerably in the upper 7.4 in (Figure 6). The Harden Index value of this surface
is 21.9, but the presence of a post-1800 year old Mono Crater ash (J.0. Davis,
writ. comm., 1987) at 3.5 in Indicates that this is a recently active surface. The
index value is probably due to the high percentage of fine sand and silt deposited
as a result of the hole's proximity to the basin center, and the low carrying
capacity of modern surface flows. The drill site is about 12 in above a modern
stream channel, but is In an environment where lateral stream shifts would have
been common (Bull, 1977). While influent-stream flow is still a possible mechanism
to explain the low chloride values at depth, they may also be Indicating a buried
stream channel. The chloride fluctuations suggest pulses of aggradation.
Wi? 5, on the other hand, appears to have recorded a recent erosional event.
WF 5's surface was mapped as Pleistocene, but Its ET peak Is very small in
comparison to WF 2, 3 and 4. The low ET values at WF 5 may be the result of: (1)
the occurrence of a west to east climatic gradient across the basin which would
decrease the amount of chloride input on the eastern side, (2) coarser grain sizes
which result in higher water fluxes through Wi? 5s ET zone, or (3) a recent
erosional event which stripped this zone.
The possibility of a strong, long-term climatic gradient across the basin
seems unlikely for several reasons. The basin is only 6.5 km wide and WF 2, 3, and
5 are approximately the same distance from the drainage divide, though elevation
and aspect vary. Wi? 5 is about 100 in higher than Wi? 2 and 3 (Table 1) and faces
northwest compared to the eastern exposure of WF 2, 3, and 4. However, the
vegetation Is similar on all surfaces.
The grain-size analyses of samples from cores Wi? 4 and 5 showed similar
values, yet Wi? 4 had significantly higher chloride concentrations. Therefore,
erosion of the Wi? 5's ET zone during the incision of the adjacent wash seems the
30
most likely explanation. The small peak at 1.1-1.7 m thus represents chloride
accumulation since stripping and the modern infiltration depth. This value is
within the range listed by Foxx et aL (1984) for vegetation types in Region 2, and
for sand and sandy loam soils. Salt-age calculations indicate that the erosional
event occurred 130-1780 years ago. The other incised channels In the basin are
probably contemporaneous.
GROUNDWATER RECHARGE RATES AND GEOMORPHIC-SURFACE AGES
Groundwater recharge calculations use the average chloride concentration below
the root zone provided it has reached a steady state. The concentrations in this
steady-state zone may represent primary chloride (deposited with the sediments),
secondary chloride (added after deposition by infiltrating waters), or leached
chloride values due to subsurface flow. Only secondary chloride values represent
recharge. However, determining if the concentrations are primary or secondary may
difficult, and requires evaluating all profiles in the area and some knowledge of
the basins geomorphic and hydrologic history. Information on soluble chloride
concentrations for different lithologies is minimal, what exists has a considerable
range, and the source of the chloride In the unweathered rock is unclear (Fouty,
1989). Cited chloride concentrations for felsic intrusives range from 1.2-193 mg/L
with a mean of 37.5 mg/L (Wedepohi et al., 1969).
An estimated range of 100-350 mm/yr of precipitation and 0.19-0.55 mg/L of
chloride input was assigned to Whisky Flat for the recharge and age calculations.
The 0.19 mg/L is the average of the Spooner Summit and Eagle Valley precipitation
values, two areas located within the Sierra. The maximum values allow for
variations through time.
Analyses indicates that WF 1, 3, and perhaps 2 have been leached at depth by
31
subsurface flow. As a result, recharge rates at Whisky Flat are calculated using
only WF 5 data. Rates obtained are 0.04-0.8 mm/yr. Values for the other Whisky
Flat sites are assumed to be equally low, especially since a hardpan exists about 1
m below the Pleistocene surfaces. Just as percolation and rooting depths probably
increased during the Pleistocene, recharge rates may have also, at least for a
while before the vegetation type and density changed. The 0.8 mm/yr is therefore
interpreted as a Pleistocene maximum rate with recharge under the more arid, modern
climate much less.
A final note regarding the depth of modern percolation is provided by WF 7's
profile (Figure 6). This drill hole [s in an ephemeral stream, yet its profile
shows an increase in chloride concentration at 5 m suggesting that deep
percolation, and thus recharge is limited under the best of modern conditions.
The age calculations require a stable, nonagradding geomorphic surface (Fouty,
1989), such as the WF 2, 3, and 4 surfaces (Figure 6). The calculated estimates
show a wide range in values, with the lower end much younger than ages suggested by
the soils and volcanic ash data (Table 3). This indicates that the precipitation
and chloride-input ranges are too broad, but in this case could not be narrowed
given the amount of available paleoclimatic information. The chloride-surfaces
ages at Whisky Flat thus contribute little in the way of specific surface dates.
However, the ages do suggest that the calculated recharge rates are representative
of at least the last 5,000 years.
CONCLUSIONS
Long-term groundwater protection requires being able to estimate recharge
rates, surface stability, and root and percolation depths under wetter conditions.
32
Table 3. Comparison of surface age estimates
Harden Modified
Soil Profile Profile Relative Drill Age Age Ash Age
Ho. Index No. Index No. Surface Age Hole Estimate Estimate2 EstImate
21 29.04 76.46
19 33.78 68.00
12 31.02 59.29
31 33.55 50.78 Pleistocene HF 4 8,500 -125,000 11,900 - 83,000
20 28.00 48.00 HF 3 8,000 -108,000 10,200- 71,800 Posslblysameash at 7.7 m
11 25.83 41.13 HF 2 5,500 - 80,000 1,600 - 53,600 Ash at 7.3 ii estimated at 47,000
9 23.55 41.64 7000 Years.
Upper limit 15.000 years
15 28.91 34.82
27 25.46 32.06
13 26.90 29.60
29 24.16 26.86
23 24.57 26.72
17 25.42 25.44
mid-early Holocene
26 23.00 23.00
18 20.25 22.70
24 18.48 21.93
5 17.56 20.41 Salt Age Equation
22 16.40 19.10 late 1olocen. (used to cilculate Age Estimates I and 2)
30 11.00 11.00
4 17.00 17.00
14 13.11 15.92
Ag. Cumulative Chloride (CC)
25 12.16 12.76
7.77 9.22
7 8.45 8.45
8 6.97 6.87
16 5.55 5.55 Active
1 5.23 5.23
6 3.03 3.03
10 3.00 3.00
1Age Estimate: PrecIpitation 0.10-0.35 rn/year. Clt 0.19-0.55 g/cu. I
2Aqe Estimate: Precipitation 15-25 rn/year, Clt 0.19-0.55 g/cu. rn
utl.ats from Oivis, writ. co., 1981
Ppt x Chloride
Age(max) CC/.15 .19
Age(mln) CC/.25 x .55
33
The wettest period experienced by Whisky Flat occurred during the Pleistocene.
This time represents a worst-case scenario with respect to the potential for
groundwater contamination due to the downward percolation of contaminated water.
Calculated recharge rates ranged from 0.04-0.8 mm/year. Rates relied on WF
5's data because the abrupt decrease in chloride concentration at depth in WF 1, 2,
and 3 Indicated leaching due to subsurface flow. The depth of this decrease varies
as a function of surface elevation and could be due to local, site-specific events
or a more regional event. A regional influence on the profiles would be a
steepened mountain front-basin center, water-table gradient and/or a basin-wide.
water-table rise due to blockage of the northern channel. This appearance of a
regional cause may be coincidental because the decrease at WF 1 may represent a
buried channel while WF 3's decrease may be the result of modern influent-stream
flow during the basin flooding events.
The 0.8 mm/year rate is assumed to be a maximum value and record recharge
conditions during the Pleistocene. The increase in chloride concentration at S m
in WF 7 suggests that deep percolation is limited, and that modern rates through
the fan sediments are very low, even under the best of modern conditions. Water
levels have steadily declined over the years In the basin due to pumping by
Sweetwater Ranch and will continue to do so under current groundwater withdrawal
rates.
The upper zones of cores WF 1-5 record different geomorphic events. WF 5 is
on a Pleistocene surface, but its upper profile records an erosional event that
occurred 130-1780 years ago. At that time Its ET peak was stripped and the 1.7 m
deep chloride peak reflects current ET depths. The wide fluctuations in chloride
concentrations In the upper 7.4 in of WF 1 and the post-1600 Mono Crater ash at 3.5
m indicates a recently aggrad.ing surface.
34
WF 2, 3 and 4 surfaces have thick upper zones with high chloride concentration
throughout and appear to be stable. Surface age estimates for WF 2, 3, and 4 range
from 5,000 to 125,000 years. This wide range is due to the inability to tightly
constrain precipitation and chloride inputs. While these estimates contribute
little in the way of specific surface dates, they do suggest that the calculated
recharge rates are representative of at least the last 5.000 years.
Comparison of the thickness of the WF 2, 3, and 4 upper zones with the
estimate of modern ET depth, indicates that root and percolation depths were
greater in the past. The long-term active root and percolation zone was defined
using WF 2's upper profile. The long-term active root zone appears to be
restricted to the upper 7.7 m. This is the zone of highest chloride
concentrations. The long-term active percolation zone extends down to 9.6 m, which
is the base of a middle zone of moderately high chloride concentrations. The
difference between these two zones may be related to the lag time between the
increase in effective precipitation during the Pleistocene and the subsequent
change in vegetation type and density which would capture the water at a shallower
depth and concentrate chloride higher in the profile.
35
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40
APPENDIX 1
FIELD PROPERTIES OF WHISKY FLAT SOILS 1
Soil Depth Texture Color Structure pH Consistence ciasts matrix (HC1No. (cm) Dry Wet (%,stage) reaction
0-8 si 1OYR 6/2 ma/m-csbk 8 la-so so, sp eo7-17 is 1OYR 7/2 ma 8 lo so, vsp mc17-38 is 1OYR 5/2 ma/.sbk S 10-so so, pa ---- ma38-58 gs 1OYR 5/3 ma 8 lo so, po 5, disc. ec
0-6 gs 1OYR 5/2 ma ---- lo so. pa ma6-IS is 1OYR 6/2 if-msbk ---- so so, vsp so19-28 is 1OYRS-5/3 lf-csbk S sh vss,sp en28-41 gs-ls 1OYR 6-5/3 ma-lfcsbk ---- b-so so, vsp ---- me47-16 gs 1OYR 5/3 ma ---- lo so. pa 70, v. disc. so
0-7 s 1OYR 5/2 ma ---- lo so, pa so7-28 is 1OYR 6/3 1m-csbk 8 so so, vsp mc28-43 vgs 1OYR 6/3 ma ---- ic so, pa ea43-13 vfs 1OYR 5/3 lm-fsbk ---- so so, vsp so73-78 gs 1OYR 5/2-3 ma ---- lo so, pa eo
0-7.5 gfs OYR 6/2 2m-clp 8 so-sb so, pa ma7.5-33 gs IOYR 5/4 2f-csbb 8 sb-h so, vsp ma33-60 gls/si 1OYR 5/3-4 2f-csbk 8 sh ss, sp ---- en60-81 egs IOYR 5/3 ma 8 10 so, pa 80, disc, ma81-94 gis 1OYR 5/3 ma/lf-msbk 8 la-so so, vsp ---- eo
0-5 gs IOYR 6(1 ma 8 la so, pa ma5-IS Is 1OYR 8/2 Icpl 8 sh so, sp me15-24 s 1OYR 6/2 1f-csbk 8 so-sb so, po eo24-48 is 1OYR 6/3 lis-csbk 8 so-sb so, sp ma48-71 gis 1OYR 6/3 lf-scbk 8 sb-h so. so 8071-79 s 1OYR 5/2 ma/lf-csbk 8 so-h so, pa ma
0-8 vgs 1OYR 6/1 ma S io so, pa ma8-15 gs 1OYR 6/2 ma/lfmsbk 8 so-sb so. pa so15-36 gs 1OYR 5/2 ma 8 10 so, vsp ---- so36-64 vgs 1OYR 6/2 ma 8 lo so, sp 5, cant.; 15, disc. es64-102 vgs IOYR 5/2 ma 8.2 10 so, vsp 33 cant.; 67, disc. ev
0-3 vgs IOYR 7/2 ma ---- lo so, pa so3-6 vgs 1OYR 1/1 ma/lm-csbh ---- so-sb so, pa ---- ma6-27 vgs 1OYR 1/2 ma/-lfmsbk 8 sh so, pa 60, v. disc. so27-44 gis 1OYR 7/2 me/lfmsbk 8 sh so, sp 30, disc. so44-56 vgs 1OYR 6/3 ma ---- lo so, pa 40, disc, ma66-95 vgs 1OYR 7/3 ma 8 lo so, pa £0, cant.; 60, disc, ma
1'Abbreviations explained at end of APPENDIX 1.
41
2
3
4
5
5
7
CaCO accumulation
Soil Depth Texture Color Structure pH Consistence clasts matrix (Nd
No. (cm) Dry Wet (%,staqe) reaction
8
0-8 s 1OYR 6/1 ma ---- 10 vii, vsp eo
8-19.5 gs IQYR 6/2 ma/lfmsbk 8 so-sh so, vip ---- cc
19.5-38 gis 1OYR 6/2 ma/lfmsbk 8 so-sh is, vip 5, disc. em
38-49 vgs 1OYR 6/3 ma 8 lo p0 ---- e
49-53 vgs IOYR 5/3 ma 8 Ic vms, po mc
53-83 vqs 1OYR 6/3 ma 8 10 50, p0 cc
9
0-9 gs 1OYR 5/2 ma 8 lo vms, vip
9021 gil 7.5YR 6/3 1-2fcsbk 8 sh-h is, sp cc21-29 vgcl 7.SYRS/3 lfcsbk 8 so-sh s,p mc
29-42 vgcl 7.5YR 6/4 1-2fcsbk 0 sh-h s. p e
42-63 vgs 1OYR 6/4 ma/2cpl 8 vh so, po cv
0-8 fs ma/lmcsbk go-sh vii, vip cc
8-22 vgs ma lo so, po cc
22-43 vgs ---- ma 10 SO. o 80
43-SI vgs 1OYR 5/2 maflfcsbk so-sh vvss, vip cc61-68 vgs ---- ii 10 50, 0 80
58-84 vgs ma )o so, po cc
87-96 vgs ma lo so, 0 90
96-106 vqs ---- ma lo so, po cc
106-125 vgs 1OYR 6/2 ma lo so, pa cc
0-5 gs 1OYR 6/2 ma 8 lo so, p0 90
5-14 gil 1OYR 6/2 clp/f-vcsbk B sh si-s. p cc14-22 gsl IOYR 7/2-3 2f-csbk 8 sh s, p eo
22-36 gil IOYR 6/2 2f-csbk 8 sh s, p cc
36-43 si 1OYR 7/2 ma/lf-csbk-abk 8 h ss, p ---- cc
43-70 eqs IOYR 6/3 3.-csbk-abk 8 h so, Pc 5, disc. cc
0-9 s 1OYR 6/2 ma 8 lo so, p0 eo
9-22 $ IOYR 6/2 lf-csbk 8 sh so, ip cc
22-36 s IQYR 6/2 ma/lf-csbk 8.2 sh so, sp cc36-47 fsl IOYR 6/2 2f-csbk 8.4 h-vh 5, p cc
47-64 ii 1OYR 5/4 2f-csbk 8.8 sh-vh 5, p i064-80 gil IOYR 6-5/4 2f-csbk 8.6 sh-vh s, sp cc
80-94 gil 1OYR 5/4 2f-vcsbk 8 h-vh vms, vsp ---- cc
94-106 gs 1OYR 5/4 ma/lf-csbk 8 lo-h-vh so, vip 5, v. disc. cc
0-5 s 1OYR 5/2 ma 8 lo so, po Co
5-13 is IOYR 6/2 2f-csbk 8 sh-h is, sp cc13-39 ii 1OYR 6/3 2f-cpl-sbk B sh-h s, p co-c39-55 Is 1OYR 5/3 2fcsbk 8 sh-h vms-is, vs co-a
55-59 is 1OYRS/3 lfcpl-sbk 8 sh-h vms-sm, vsp 40,v.disc. co-c
69-17 s 1OYR 6/2 1-2fcsbk 8 so-ih so, vsp 60, v. disc. as
77-94 s IOYR 6/2 ma 8 lo so, vip 50, v. disc. ci
0-9 s 1OYR 7-6/2 mm 8 lo so, po cc
9-44 s 1OYR 7-6/2 m-cpl-mcsbk 8 sh so, p0 cc44-50 gs 1OYR 6/2 ima/lf-csbk 8 sh so, po cc
50-53 1 1OYR 7/2 3f-csbk 8 sh s, p cc
53-78 gls IOYR 5/3 lf-csbk 8 sh-h is, ip e
78-82 is 1OYR 6/2 ma/lf-csbk 8.4 sh-h is, sp ci82-92 sI 7.5YR 7/2 2f-csbk 8.6 sh-h s, p em
42
10
11
12
13
14
CaCO accumulation
SOil Depth Texture Color Structure pH Consistence clasts matrIx (HC1
No. (cm) Dry Wet (%.stage) reaction
92-100 is 1OYR 6/2 isa 8 lo ss, sp so
15
0-4 $ 1OYR 6/2 ma 8 lo so, po so
407 s 1OYR 1/2 m-vcpi 8 sh so, vsp so
7-30 1 7.SYR 5/3 2f-csbk 8 sh-h s, p so
30-44 s 1OYR5.3 lf-csbk 8.4 so-sI, vss,vsp so
44-59 is 1OYRS/4 2f-csbk 8.8 sI, ss,sp so
59-79 is 1OYR 5/3 iwa/lf-csbk 8.6 sh vss, sp S0
79-87 s 1OYR 5/2 ma/lf-csbk 8.6 sh vss, yap so
16
0-7 gs IOYR 6/1-2 ma 8 lo so, vsp so
7.-28 gs IQYR 6/1 ma/lf-csbk 8 so-sI, so, pm so
28-39 vgs IOYR 6/2 mm 8 10 50, p0 so
39-60 gs 1QYR 6/2 isa/lf-msbk 8 sI, vss, vsp so
60-68 gs 1OYR 7/2 ma 8 lo 50, Pc so
17
0-7 gs 1OYR 6/2 ma 8 io so. po so
7-li si IOYR 6/2 f-cpi 8 sh ss, p so
14-27 1 7.5YR 6/3 m-cpl/fcsbk 8 sh s, p cc
27-34 si 1OYR 6/3 2-3f-csbk 8 sh s, p so
34-41 gis 1OYR5/3 mallf-csbk 8 sI, $S,sp eo
41-72 gs 1OYR 6/3 3f-vcsbk-abk 8 vh so, po so
72-87 gs 1OYR 6/3 ma 8 io so, po so
18
0-10 s 1OYR 5/2 ma io so, p0 ---- so
10-20 fs IOYR 6/2 m-vcpi SI, so, vsp <5, disc, so
23-25 is 1OYR 5/2 2f-csbk sh vu, sp 5, disc, so
25-39 gifs IOYR 6/3 2f-csbk sh vss, sp <5, disc, so
39-59 gis 10YR6/3 3f-csbk-abk ---- h ss,sp 5, disc. cc
59-74 gfs IOYR 5/2 2f-csbk-abk 8 sI, So, p0 30, disc. e
14-89 gs 1OYR 63 mm 8 io so, p0 10, disc. so
19
0-9 gs 1DYR 5/2 ma 8 lo so, po cc
9-IS $ 1OYR 1/1-2 2vcpl 8 SI, SO, VSp 50
15-21 IOYR 7/2 lf-csbk 8 sh SO, p0 cc
21-34 s 1OYR 7-6/2 lf-msbk 8 so. so, P0 ---- so
34-47 i 7.5YR 7/2 3f-msbk 8 h-vh a, p 10, disc, so
47-57 is 1OYR 6/2-3 3f-msbk B h ss, sp <10, v.disc. so
57-72 s 1OYR 6/3 3c-vcabk 8 eh so, po 20, disc. e
72-90 a 1OYR 6/4 3f-vcsbk-abk 8 vh so, Pc 10, disc. e
90-97 gs IDYR 5/2 na 8 10 50, po ---- cv
20
0-9 5 IOYR 5/2-6/2 ma 8 lo so, po so
9-17 is 1OYR 7/2 2vcpl 8 so-sI, so, sp ci
17-28 5 IQYR 7/1 mm/lf-csbk 8 so-sI, so, po so
28-44 si 1OYR 6/2 3f-csbk 8.6 vh s, p so
44-57 1 1OYR 5/3 3f-csbk 8.8 vh s, p ---- cv
57-70 1 1OYR 8/1 3f-cbk 8.8-9 sh-i, s, p 80, dIsc. cv70-76 s IOYR 7/2 ma 8.8 10 50, sp ---- cv
43
CaCO accumulationSoil Depth Texture Color Structure pH Consistence clasts matrix (HCINo. (cm) Dry Wet (%,stage) reaction
0-8 gs IDYR 6/2 ma 8 la so, pa8-14 gs IOYR 6/2 ivcpl a so so, vsp14-36 1 IOYR 6/2 3f-msbk 8 sh-h s, p36-51 s IOYR 6/3 3f-cabk-sbk 8 vh so, yap disc.51-74 s 1OYR 8/1 3f-csabk 8.4-8.5 vh so, pa 80, dics14-89 gs 1OYR 6/2 ma 8 lo so, pa 5, disc.46-56 ci ---- 3f-csbk ---- vh Vs. V
0-7 vgs IOYR 6/1 ma 8 lo so, pa 807-18 $ IOYR 5/2 lvcpl 8 so sp ---- 8018-50 gs 1OYR 6/2 ma/tf-mabk 8 sh so, vsp <5, disc. eo50-16 vgls 1OYR 6/2 lf-csbk 8 sh vms, ap 20, disc, em76-104 vqs 1OYR 1/2 ma/lf-msbk 8 mo-sh so, pa 20, disc. cv104-121 gs 1OYR 7/2 ma 8 lo so, VSP 15, dIsc. cv
0-8 s IOYR 7/4 ma B Ia so, pa8-18 s 1QYR 7/4 3m-vcpl 8 sa-sh so, vso18-34 gs 1OYR 1/3 3f-vcsbk 8 h-vh so, pa34-43 vgsl 1OYR 7-6/3 3f-sbk B vh ss, p 10, V. disc.43-61 vgls I0YR 6/3 3f-csbk 8 vh mm, sp61-74 vgls 1OYR 6/4 3t-csbk-abk 8 h 55. pa 10, disc.74-84 vgs IOYR 7/3 2m-csbk 8 so, pa 40, disc.84-92 gs IOYR 6/3 ma 8 lo so, pa <5, disc.
0-4 5 1OYR 6/1-2 ma lo so, pa4-7 si 1OYR 7/1 vcpl ---- sh s, p7-17 1 1OYR 6/2 if-msbk 8 sh s, vp17-44 si IOYR 6/2 2f-csb-abk 8 sh-h s, p44-76 s 1OYR 6/2 mi 8.2 lo so, vsp74-93 s IQYR 6/2 ma 8.4 lo so, Ymp
0-3 $ IOYR 6/2 ma 8 10 50, yap 803-28 is IOYR 7/2 ma 8 10 ss, sp ---- as28-43 ml 1OYR 7/3 ma/if sbk B so-sh ss, p 5, V. disc. ev43-53 ls IOYR 1/2 ma/1f-asbk 8 so-sh mm, sp 5, v. disc. ev53-74 vsl IQYR 7/2 ma/tf-imsbk 8 lo s, p 100. cont. es
0-5 gi 1OYR 5/2 ifvf 7.2 so ss, pa6-14 gi IOYR 5/2 ifvf-sbk 7.4 so mm, pm14-30 gi 1OYR 5/3 lfsbk 7.4 sh s,p30-43 gi 1OYR 5/3 Iinabk-sbk 1.4 sh s,p43-60 gi 1OYR 5/3 lmf-sbk 7.4 h s,ps60-84 g1 1OYR 6/4 if-sbk 7.6 h ss,ps84-106 gl 1OYR 6/4 lf-sbk 7.8 sh ss,ps105-127 gsl 1OYR 6/4 ma 8.2 sh ss,ps127-140 gsl 1OYR 6/4 ma 8 sh ma. pm
0-7 gs 1OYR 6/3 ma B 1 so, pa7-15 is 1OYR 7/2 2vcpl 8 so-sh vms, pa15-29 gsl 1OYR 6/3 31-csbk 8 sh mm, sp29-40 mc 1OYR 5/4 3f-vcsbh ---- sh-h40-57 gsl 1OYR 5/4 3f-mabk-sbk sh57-59 gs IQYR 6/6 ma/lf-esbk sh-h69-82 gs 10YR 6/6 ma 10
44
90
so
80
<5, disc. 80
a
80
80
80
80
80
50
90
20, disc. eSO. disc. e
eo
80
eo5, Vp 80ss, sp 80vsp, so 50so, pa eo
21
22
23
24
25
26
27
CaCO accu.ulatlonSoil Depth Texture Color Structure p$ Consistence clasts matrix (HC1No. (cm) Dry Wet (%,stage) reaction
28
0-9 vgs 1OYR 6/2 isa 8 lo so, pc so
9-16 vqls IOYR 1-6/2 f-spl 8 so ss, sp so
18-25 1 IOYR 6/3 3-msbk-abk 8 h-vh 5, p so
25-40 gd IOYR 5/4 3f-vcsbk-abk 8 h-vh vs. vp ---- so40-64 vgs IOYR 5-6/3 2f-mabk 8 Wi so, p0 60, disc. so
84-79 eqs IQYR 5/3 ma 8 lo so, po 50, disc. e
79-85 eqs IOYR 5/3 ma 8 10 so, p0 50, v. disc. so
29
0-4 gs IOYR 8/2 ma lo so, p0 so
8-8 fs 1OYR 1/2 c-vcpl sh so, vsp so
8-23 c 1OYR 6/3 2f-esbk sh-h VS, VP 50
23-39 gc 1OYR 5/3 2f-msbk sh-h vs, vp so
39-52 gsc 1OYR 5/4 3t-sabk-sbk s-vs, vp eo
0-6 gs 1OYR 4-3/4 ma 8 lo SO, p0 90
6-14 s IOYR 4/4 p, f-s 8 sh vu, vsp so
14-23 gsl 7.SYR 4/3 Zf-csbk 8 sh p. u so
23-31 ci 1.4YR 5/4 2f-msbk 8 sh vp, s so
31-50 gs 1.5YR 4/6 2f-csbk 8 eh vsp, vss ---- mc
50-89 vqs 1OYR 4/3 ma 8 lo so, p0 <5, dIsc, so
12-81 eqs IOYR 4/4 3-vcsk-abk 8 eh so, P0 <5, disc.
0-9 s 1OYR 4/3 ma 10 80, po so
9-21 s IOYR 4/3 plf-c sh so, po so
21-41 is IOYR 4/3 2-31-csbk sh so, vsp so41-58 is 1OYR 4/3 1f-msbk s-sh so, vsp so58-71 si 1OYR 4/4 3f-vcsbk h ss-s, sp-p so
71-85 sd I0YR 4/4 2f-csbk sh s, p ---- so
85-94 s 1OYR 4/4 2f-vcsbk h so. 0 10, V. disc, so
94-110 gs IOYR 4/4 lp-csbk-abk h so, p0 ---- so
110-119 gs 1OYR 4/4 ma lo so, po 5-10, disc. so
45
30
31
Soil property
EXPLANATION OF SOIL-PROPERTY ABBREVIATIONS
texture(gravel) gr gravelly
vgr very gravellyegr extremely gravelly
(fines) s sandfs fine sandls loam sandsl sandy loam
sd sandy clay loamcl clay loam!
structure vf very fine(size) f fine
m mediumc coarse
ye very coarse(form) ma massive
sg single grainsbk subangular blockyabk angular blocky
consistence(dry) lo loose
so softsh slightly hardh hard
vh very hard(wet) so non-sticky
vss very slightly stickyss slightly stickys sticky
vs very stickypo non-plastic
vsp very slighty plasticPS slightly plasticp plastic
Carbonate accumulation(clasts)
(matrix;UCI reaction)
Notation Explanation
0-100 percentage of clasts inhorizon WI CO3 accumulation
eo non-effervescente effervescent
es strongly effervescentev extremely effervescent
46
APPENDIX 2.
HARDEN INDEX VALUES AND MODIFIED INDEX VALUE
HardenProfileIndex No.
ModifiedProfileIndex No.
1 5.23 5.232 7.77 9.223 8.7 8.74 17.0 17.05 17.56 20.416 3.03 3.037 8.45 8.458 6.87 6.879 23.55 41.6410 3.0 3.011 25.83 47.1312 37.02 59.2913 26.9 29.614 13.17 15.9215 28.97 34.8216 5.55 5.5517 25.42 25.4418 20.25 22.719 33.78 68.020 28.0 48.021 28.04 76.4622 16.4 19.123 24.57 26.7224 18.48 21.9325 12.78 12.7626 23.0 23.027 25.46 32.0628 24.16 26.8629 33.5230 17.0 17.031 33.56 50.78
A diagnostic feature of relative geomorphic-surface age atWhisky Flat was the degree of hard-pan development. Some of thesoils had similar Harden values, but significantly different degreesof pan development. This characteristic is not included in theHarden Index, but was factored in later using a semi-quantitativetest to determine aggregate strength. Aggregate strength wasdefined as the time it took an aggregate to dissolve in water(disaggregation time). Values assigned to the different timeintervals were arbitrary because the intent was to weight thehard-pan development. A disaggregation time of less than 1 minute= 5 points; 1 minute = 10 points; 3 minutes 20 minutes; > 3minutes = 30 points; and > 25 minutes = 50 points.
47
SoilNo.
APPENDIX 3
DRILL CORE SIEVE ANALYSES
48
Dril
l Cor
e S
ieve
Ana
lysi
s ex
clud
ing
grav
elpe
rcen
t
Sam
ple
No.
-D
rill H
ole
Sam
ple
Dep
th(m
)P
erce
nt
%S
and
base
d on
wei
ght
%S
ilt
afte
r si
evin
g
%C
lay
Soi
l Tex
ture
53C
13.
591
72
San
d
61 C
14.
785
114
Loam
y sa
nd
69C
15.
986
140
Loam
y sa
nd
83C
114
.384
1 6
0Lo
amy
sand
89C
-2
0.3
7619
6S
and
97C
23.
196
40
San
d
1168
27.
894
60
San
dy lo
am
147C
218
.766
1815
San
d
1578
31.
1'
937
0C
lay
167
32.
90
1585
San
d
171B
33.
599
10
San
d
1818
35.
490
91
San
dy lo
am
193B
38.
469
238
San
dy lo
am
2238
40.
572
1513
Loam
y sa
nd
231B
42.
385
123
San
d
235B
43.
289
82
San
dy lo
am
241B
44.
372
1414
Loam
y sa
nd
245B
45.
885
131
San
d
263B
51.
610
00
0S
andy
cla
y lo
am
283
54.
469
1120
San
d
293
58.
195
22
San
d
306
512
.210
00
0S
and
319
515
.889
92
San
d
333
70.
210
00
0S
and
339
70.
825
2153
Cla
y
345
71.
666
1321
San
dy c
lay
loam
Dril
l Cor
e S
ieve
Ana
lysi
s in
clud
ing
grav
el p
erce
nt
Sam
ple
No.
Dril
l Hol
eD
epth
(m)
% G
rave
lPer
cent
bas
ed o
n
% S
and
wei
ght a
fter
siev
ing
% S
ilt%
Cla
yS
oil T
extu
re
53C
13.
518
847
2S
and
61C
14.
724
8211
4Lo
amy
sand
69C
15.
940
8614
0Lo
amy
sand
83C
114
.33
083
160
Loam
ysan
d89
C2
0.27
869
1 7
5Lo
amy
sand
97C
23.
086
914
0S
and
116B
27.
772
925
0S
and
147C
218
.75
4536
108
V.
grav
elly
san
dy lo
am15
7B3
1.07
1183
60
Gra
velly
san
d16
73
2.90
680
527
Gra
velly
cla
y17
183
3.50
099
10
San
d18
183
5.40
090
91
San
d19
3B3
8.38
368
227
San
dy lo
am22
3B4
0.46
767
1412
San
dy lo
am23
1B4
1.40
779
113
Loam
y sa
nd23
584
1,80
684
82
San
d24
184
3.35
1462
1212
Gra
velly
san
d24
584
5.47
1 3
741
21
Gra
velly
san
d26
3B5
1.65
4555
00
Gra
velly
san
d28
35
4.42
3457
92
Gra
velly
san
dy c
lay
loam
293
58.
0841
561
1V
.gr
avel
ly s
and
306
512
.19
3862
00
V.
grav
elly
san
d31
95
15.8
534
586
2V
.gr
avel
ly s
and
333
70.
2449
500
0V
.gr
avel
ly s
and
339
70.
8884
43
8V
.gr
avel
ly c
lay
345
71.
5964
245
8V
.qr
avel
ly s
andy
cla
y lo
am
1
APPENDIX 4
EQUATIONS USED IN THE COMPUTER PROGRAMS
CHLORIDE IN THE SOIL WATER (CLsw)
Clsw = [Cle X (Wtr added/Dry Wt)]/ ([(Wet Wt - Dry Wt) X pb]/Dry Wt}
Clsw = Chloride in soil water (mg/I)Cle = Chloride in the extract (ppm)Wtr added Amount of dionized water added to sample (g)Dry Wt Weight of oven dried sample (g)Wet Wt Weight of sample and water (g)
Bulk density (g/cu. cm)
pb = 1.5 g/cu. cm for Whisky Flat
CUMULATIVE CHLORIDE (CC) AT A GIVEN DEPTH
CC = (Clsw X L)
CC = Cumulative chloride (g/sq. ni.)
L = Sample interval length (in)Clsw = Chloride in soil water (g/cu. in..)
VOLUMETRIC WATER CONTENT (Vwc)
Vwc = [(Wet Wt. - DryWt.) X b] / Dry Wt.
Stone, 1986; written communication
51
1
APPENDIX 5
CHLORIDE CONCENTRATION VALUES FOR WHISKY PLAT NEVADA
Note:
WF 1 = Whisky Flat drill hole # 1
Dry Wt. Soil = Weight of soil used in salt extraction
Wt. Wtr Added = Weight of deionized water in salt extraction
Volumetric moisture contents are rounded to the nearest hundredth inthe table, but Clsw calculations are based on true value.
52
wF1
Samp4e No. Sample Depth Moisture Dry Wt. Wt. Wtr CI in Cl in(m) Content Soil Added x1ract Soil Wtr.
(Cu. rn/cu. m) (gm) (gm) (ppm) (mg/I)
53
25 0.09 0.09 21.84 87.23 0.50 21.5226 0.18 0.08 28.26 81.72 0.50 18.5327 0.27 0.05 30.74 81.74 2.90 142.5128 0.37 0.03 42.95 84.24 4.30 300.1229 0.46 0.03 40.58 82.84 9.50 583.2031 0.55 0.03 32.40 80.50 11.00 986.2832 1.20 0.05 28.00 83.52 86.00 4894.5133 1.30 0.03 34.79 81.03 94.00 6413.1434 1.40 0.03 46.51 80.26 127.00 8045.9835 1.46 0.04 35.13 80.00 112.00 7283.1736 1.52 0.07 33.40 81.43 149.00 5542.2537 1.83 0.04 27.48 81.73 85.00 5814.4938 1.92 0.05 36.52 79.30 150.00 6557.6739 2.01 0.04 36.97 82.35 145.00 7653.0340 2.10 0.05 35.15 80.75 139.00 6197.4541 2.19 0.04 38.10 82.39 115.00 6743.8242 2.30 0.04 37.59 85.89 135.00 7295.5943 2.35 0.05 22.52 86.77 70.00 4993.9444 2.59 0.03 30.30 85.47 72.00 6756.8045 2.68 0.02 36.21 80.24 88.00 7847.0846 2.80 0.03 47.89 82.58 86.00 5418.6247 2.90 0.03 42.55 78.88 59.00 3638.3048 3.00 0.03 39.72 81.63 68.00 4444.5749 3.11 0.02 35.10 80.37 86.00 7939.0250 3.17 0.04 30.71 75.04 97.00 6551.3152 3.35 0.05 31.82 82.87 94.00 5362.9253 3.51 0.05 35.28 90.75 90.00 4930.6554 3.86 0.07 32.21 83.45 145.00 5079.3855 3.81 0.06 31.42 80.26 115.00 5279.5656 3.96 0.05 32.52 81.09 98.00 5160.9157 4.11 0.04 30.75 78.90 74.00 4221.1858 4.27 0.06 36.44 78.59 125.00 4195.4159 4.42 0.10 21.77 85.93 102.00 4132.7760 4.57 0.05 37.03 109.40 122.00 6988.3861 4.72 0.06 22.49 79.45 90.00 5393.4863 4.88 0.05 31.88 93.91 68.00 4436.4964 5.03 0.03 45.36 82.14 66.00 4013.2965 5.18 0.04 33.63 84.48 63.00 3549.3066 5.33 0.10 28.82 83.08 114.00 3298.0667 5.49 0.04 29.81 99.74 55.00 4231.8268 5.64 0.10 24.73 80.55 100.00 3252.2769 5.94 0.11 26.23 81.27 139.00 4015.3470 6.25 0.12 24.49 81.77 152.00 4400.1271 6.40 0.15 24.97 82.45 180.00 4007.1872 6.55 0.08 29.87 88.46 100.00 3466.8773 6.71 0.10 24.82 81.79 101.00 3298.5374 7.16 0.11 2521 92.78 160.00 5419.4075 7.47 0.05 23.41 80.98 40.00 3049.1677 10.21 0.01 64.82 81.52 4.00 776.38
wri
54
Samp'e No. Sample Depth Moisture(m) Content
(Cu. rn/cu. m)
Dry Wt.Soil(gm)
Wt. WtrMded
(gm)
CI InExtract(ppm)
Cl inSoil Wtr.
(mg/i)
79 13.26 0.12 60.17 82.19 11.00 129.6781 13.72 0.08 33.10 79.87 1.60 48.6182 14.02 0.11 32.25 81.76 1.80 40.0883 14.33 0.11 27.06 80.87 1.60 42.4084 14.57 0.10 26.51 85.68 1.40 45.8085 14.78 0.09 29.80 83.01 1.50 44.3086 15.09 0.11 29.41 82.77 1.80 45.11
WF 2
55
Sample No. Sample Depth(m)
MoistureContent
(cu. rn/cu. m)
Dry Wt.Soil
(gm)
Wt. Wtr.kkd
Cl inExtract(ppm)
Ci InSoil Wtr.
(mg/I)(gm)
87 0.00 0.05 31.78 82.00 1.90 99.8488 0.15 0.09 20.40 48.79 2.10 88.5789 0.27 0.04 25.56 81.48 1.90 154.0491 0.49 0.04 39.77 82.79 3.30 161.1092 0.58 0.05 37.22 80.34 4.50 215.1493 2.59 0.03 42.16 82.69 38.00 2719.8994 2.74 0.03 47.53 82.10 47.00 2826.8995 2.90 0.03 40.07 84.29 35.00 2694.8797 3.08 0.04 32.03 81.94 82.00 4765.3198 3.35 0.07 31.93 80.70 60.00 2322.3099 3.51 0.08 41.05 79.39 160.00 5259.79100 3.66 0.12 27.08 84.29 180.00 4682.78101 3.81 0.05 36.18 81.03 123.00 5356.96102 3.96 0.05 29.36 83.05 140.00 7849.02104 4.11 0.09 34.61 81.04 172.00 4727.71106 4.42 0.03 33.57 80.87 70.00 5469.47107 4.57 0.02 47.07 81.27 72.00 5418.00109 4.88 0.04 31.09 86.37 76.00 5270.69110 5.49 0.02 51.19 80.09 60.00 5523.45111 5.94 0.04 40.33 80.97 98.00 5185.03113 6.55 0.04 35.32 83.52 100.00 5512.87114 7.16 0.02 45.83 85.59 36.00 3603.79116 7.77 0.04 37.69 81.72 58.00 3221.76118 8.69 0.03 91.65 85.15 58.00 1903.16120 9.30 0.03 96.99 83.54 41.00 1268.57123 9.60 0.08 91.05 81.65 105.00 1147.69126 10.18 0.11 105.08 83.68 123.00 904.05127 10.70 0.07 64.39 83.20 46.00 807.43130 11.74 0.09 51.55 83.82 24.00 435.43133 12.65 0.06 80.40 80.83 20.00 353.36136 13.44 0.18 49.99 82.28 13.10 121.38139 14.02 0.01 133.17 79.42 3.50 203.64140 16.31 0.03 40.45 81.83 5.60 386.61145 17.37 0.04 33.03 82.18 1.70 101.97147 18.75 0.11 29.40 87.31 1.65 45.92149 19.36 0.06 28.77 80.65 1.55 77.81151 19.51 0.07 31.20 82.60 1.60 82.91153 20.12 0.07 28.58 83.26 1.60 66.82
WP 3
56
Sample No. Sample Depth(m)
MoistureContent
(Cu. rn/Cu. m)
Dry Wt.Soil
(gm)
Wt. Wtr. CI inExtract(ppm)
Cl inSoil Wtr.
(mg/I)(gm)
154 0.00 0.01 49.21 82.39 3.00 588.50155 0.15 0.10 27.63 81.90 3.20 96.67156 0.24 0.10 30.08 83.84 12.80 361.57157 1.07 0.06 39.74 82.12 195.00 6352.92158 1.19 0.05 48.86 84.25 180.00 5895.54159 1.28 0.05 35.76 81.34 150.00 6256.92160 1.83 0.03 48.81 80.41 119.00 5745.85162 2.01 0.04 39.79 83.23 100.00 5837.76164 2.20 0.04 38.98 88.47 100.00 6211.61165 2.59 0.06 43.59 88.59 170.00 6239.00166 2.74 0.10 32.65 83.50 245.00 6343.41167 2.90 0.18 20.72 83.82 250.00 5658.60169 3.11 0.27 21.09 82.37 401.00 5792.05170 3.35 0.04 47.85 88.19 110.00 5091.27172 3.66 0.07 37.67 83.60 120.00 3673.75174 3.96 0.16 24.70 85.35 130.00 2762.31178 4.57 0.21 35.58 86.49 155.00 1764.83179 4.88 0.08 36.55 92.00 58.00 1891.68180 5.18 0.07 33.74 89.49 36.00 1413.00181 5.40 0.07 26.80 80.32 29.00 1194.50182 5.64 0.07 32.62 93.82 29.00 1012.51183 5.94 0.13 19.96 81.60 22.50 715.43184 6.40 0.04 39.60 80.02 12.50 611.77185 6.71 0.02 49.23 81.66 14.00 1190.87188 7.16 0.04 41.98 81.30 9.80 530.91189 7.47 0.03 40.34 81.44 1.70 130.00190 7.71 0.03 38.90 80.84 1.50 113.86191 7.93 0.17 28.79 89.00 2.20 41.03193 8.38 0.17 35.84 82.53 2.70 36.95196 9.14 0.09 31.22 82.33 1.80 55.50198 9.60 0.11 32.40 82.15 2.00 46.61199 9.91 0.05 29.66 84.18 1.60 96.03201 10.36 0.10 29.62 81.80 2.20 61.40203 10.97 0.05 37.73 83.02 1.80 80.02204 11.28 0.06 31.91 86.81 1.70 80.39
wF 4
57
Sample No. Sample Depth(m)
MoistureContent
(Cu. rn/cu. m)
Dry Wt.Soil(gm)
Wt. Wtr. CI inExtract(ppm)
CI InSoil Wtr.
(mg/I)(gm)
218 0.00 0.01 37.95 84.73 4.40 689.30219 0.09 0.04 29.72 84.25 3.30 219.91222 0.37 0.15 25.90 80.15 33.00 675.05223 0.46 0.13 29.29 83.55 69.50 1574.13224 0.55 0.08 29.01 88.49 94.00 3688.00225 0.64 0.10 19.27 84.50 125.00 5244.07227 0.73 0.18 19.49 85.94 110.00 2685.41228 0.91 0.03 36.09 85.62 37.50 2663.76229 1.22 0.05 46.16 87.71 99.00 3784.39230 1.31 0.04 48.99 90.76 85.00 4145.94231 1.40 0.03 51.96 63.13 69.00 3224.78232 1.49 0.03 40.66 82.23 84.00 5680.84233 1.58 0.02 46.10 84.51 90.00 6946.01234 1.71 0.02 43.06 85.99 96.00 8460.80235 1.80 0.05 42.75 84.55 260.00 9381.26236 2.23 0.06 37.18 86.92 200.00 8491.77237 2.41 0.05 33.71 82.19 175.00 8378.82238 2.90 0.03 45.84 80.76 145.00 8575.16239 3.05 0.04 41.51 84.87 153.00 8822.79240 3.20 0.04 45.49 93.79 155.00 8955.98241 3.35 0.03 40.91 80.92 130.00 8230.50242 3.90 0.03 51.02 81.58 125.00 6990.73243 4.27 0.09 35.23 84.35 330.00 8677.58244 4.88 0.04 38.46 97.46 132.00 8482.73245 5.47 0.04 39.48 80.83 104.00 5712.79246 5.79 0.04 47.24 83.50 135.00 5907.30
WP 5
58
Sample No. Sample Depth(m)
MoistureContent
(cu. rn/cu. m)
Dry Wt.Soil
(gm)
Wt. Wtr.ktiød
Cl inExtract(ppm)
Cl inSoil Wtr.
(mg/I)(gm)
246 0.00 0.01 37.43 81.23 2.20 475.53247 0.09 0.03 34.93 89.12 2.20 213.79248 0.18 0.03 39.86 83.44 2.40 149.52249 0.27 0.04 37.20 83.06 2.30 115.38250 0.37 0.03 31.37 80.45 1.90 145.11252 0.55 0.03 31.63 85.81 2.00 211.21253 0.64 0.02 35.16 84.83 1.80 230.83254 0.73 0.03 40.12 81.28 1.80 141.00255 0.82 0.03 39.60 83.39 2,50 179.95256 0.91 0.02 42.52 90.69 3.30 315.80258 1.10 0.02 25.37 82.83 8.20 1736.75260 1.37 0.02 43.83 82.97 9.60 882.13262 1.55 0.03 48.91 85.50 15.00 907.34264 1.74 0.04 43.66 85.45 13.00 724.38266 1.92 0.03 39.95 87.57 8.00 582.48267 2.13 0.02 36.20 87.52 5.00 502.15268 2.29 0.02 48.36 80.19 4.90 443.62270 2.47 0.03 45.08 83.27 5.60 403.02273 2.74 0.05 33.68 86.17 5.80 313.21275 3.05 0.03 36.21 91.66 4.80 472.17277 3.35 0.03 33.46 83.26 4.40 420.08278 3.51 0.03 39.61 87.86 6.60 464.47280 3.81 0.03 37.15 81.77 8.20 512.04282 4.27 0.04 39.63 88.08 9.90 552.11283 4.42 0.08 32.86 85.71 19.00 590.09285 4.88 0.10 30.18 85.62 25.20 701.60286 5.18 0.08 27.53 99.63 19.50 853.07287 5.79 0.05 35.59 80.56 14.50 663.54289 6.40 0.08 26.44 82.91 13.50 538.26290 6.71 0.04 29.95 87.02 8.60 645.78292 7.22 0.04 41.01 82.58 10.90 511.76293 8.08 0.04 37.28 84.17 10.00 565.28295 8.84 0.04 42.24 94.57 13.50 764.79297 9.45 0.05 36.61 82.01 10.00 491.21298 9.75 0.10 36.13 82.37 22.00 492.38300 10.36 0.04 42.87 91.83 13.00 741.36302 10.97 0.11 32.17 81.39 21.00 492.18303 11.13 0.12 33.36 83.52 21.50 465.94305 11.89 0.04 35.17 83.08 7.40 480.82306 12.19 0.03 34.38 82.15 4.60 330.33308 12.65 0.03 41.23 88.97 5.20 380.04310 13.26 0.03 36.42 88.17 5.20 476.67312 13.87 0.05 29.12 112.99 6.00 489.74314 14.33 0.04 34.61 82.56 5.50 367.89315 14.83 0.06 32.19 82.13 7.40 328.18317 15.24 0.06 30.39 87.99 6.80 351.60319 15.85 0.06 33.14 89.22 7.20 315.70322 17.07 0.05 30.45 84.22 4.80 241.84323 17.98 0.07 28.25 87.70 6.40 284.32325 18.59 0.06 39.85 85.64 7.40 247.65326 18.81 0.04 37.62 89.79 4.40 288.59
WF 7
59
Sample No. Sample Depth(m)
MoistureContent
(Cu. rn/cu. m)
Dry Wt.Soil
(gm)
Wt. Wtr. Cl inExtract
(gm)
Cl inSoil Wtr.
(mg/i)(gm)
331 0.00 0.06 33.89 82.82 2.30 92.67332 0.15 0.04 35.10 103.00 1.70 131.12333 0.24 0.05 33.18 86.16 1.70 83.41335 0,46 0.09 30.80 95.90 1.90 65.27336 0.55 0.12 27.66 81.77 2.50 62.49337 0.64 0.13 22.54 83.01 2.30 64.85338 0.73 0.12 25.43 82.83 2.00 54.90339 0.88 0.13 30.55 84.26 2.70 58.75340 0.91 0.17 35.85 87.40 3.30 48.10341 1.07 0.19 44.27 83.80 6.40 64.13342 1.16 0.14 21.97 86.83 4.90 134.37343 1.37 0.10 32.63 81.42 4.30 102.34344 1.46 0.06 35.31 84.66 3.90 144.77345 1.59 0.12 32.95 82.15 5.20 107.00347 2.13 0.11 37.20 89.59 4.60 104.38351 2.59 0.11 33.10 84.60 20.00 475.81355 3.08 0.03 29.09 81.52 15.00 1405.03356 3.35 0.13 27.22 87.42 8.80 211.93361 4.12 0.12 32.66 93.13 24.00 551.37362 5.33 0.10 40.71 83.13 220.00 4447.59384 5.64 0.03 53.20 89.09 92.00 4552.63365 5.79 0.04 50.30 92.05 88.00 4424.69
Note:
APPENDIX 6
CUMULATIVE CHLORIDE VALUES FOR WHISKY FLAT, NEVADA
WF 1 = Whisky Flat drill hole # 1
Gum. Cl in Soil Water Cumulative chloride in soil water
Vol. Water Content = Volumetric water content
Gum. Vol. Water Content Cumulative volumetric water content
60
Sam
ple
No.
Sam
ple
Dep
thS
ampl
e In
terv
alM
oIst
ure
(m)
Leng
thC
onte
nt(m
)(C
u. r
n/cu
. m)W
F1
din
Clin
Soi
l Wat
erS
oil W
ater
(g/c
u. m
)(g
/sq
. m)
Cum
. Cl
In S
oil W
ater
(g/s
q.rn
)
Vol
. Wat
erC
um. V
ol.
Con
tent
Wat
er C
onte
nt(m
)(m
)
250.
090.
090.
091.
940.
170.
170.
008
0.00
826
0.18
0.09
0.08
1.48
0.13
0.30
0.00
70.
015
270.
270.
090.
057.
130.
640.
940.
005
0.02
280.
370.
100.
039.
000.
901.
840.
003
0.02
3
290.
460.
090.
0317
.50
1.57
3.41
0.00
30.
026
310.
550.
090.
0329
.59
2.66
6.07
0.00
30.
029
321.
200.
650.
0524
4.73
159.
0716
5.14
0.03
30.
062
331.
300.
100.
0319
2.39
19.2
418
4.38
0.00
30.
065
341.
400.
100.
0324
1.38
24.1
420
8.52
0.00
30.
068
351.
460.
060.
0429
1.33
17.4
822
6.00
0.00
20.
0736
1.52
0.06
0.07
387.
9623
.28
249.
280.
004
0.07
4
371.
830.
310.
0423
2.58
72.1
032
1.38
0.01
20.
086
381.
920.
090.
0532
7.88
29.5
135
0.89
0.00
50.
091
392.
010.
090.
0430
6.12
27.5
537
8.44
0.00
40.
095
402.
100.
090.
0531
9.87
27.8
940
6.33
0.00
50.
1
412.
190.
090.
0426
9.75
24.2
843
0.61
0.00
40.
104
422.
300.
090.
0429
1.82
26.2
645
6.87
0.00
40.
108
432.
350.
050.
0524
9.70
12.4
846
9.35
0.00
30.
111
442.
590.
240.
0320
2.70
48.6
551
8.00
0.00
70.
118
452.
680.
090.
0215
6.94
14.1
253
2.12
0.00
20.
12
462.
800.
120.
0316
2.56
19.5
155
1.63
0.00
40.
124
472.
900.
100.
0310
9.15
10.9
156
2.54
0.00
30.
127
483.
000.
100.
0313
3.34
13.3
357
5.87
0.00
30.
13
493.
110.
110.
0215
8.78
17.4
759
3.31
0.00
20.
132
503.
170.
060.
0426
2.05
15.7
260
9.03
0.00
20.
134
523.
350.
180.
0526
8.15
48.2
765
7.30
0.00
90.
143
533.
510.
160.
0524
6.53
39.4
569
6.75
0.00
80.
151
543.
660.
150.
0735
5.56
53.3
375
0.08
0.01
10.
162
553.
810.
150.
0631
6.77
47.5
279
7.60
0.00
90.
171
563.
960.
150.
0525
8.05
38.7
183
6.31
0.00
80.
179
574.
110.
150.
0416
8.85
25.3
386
1.64
0.00
60.
185
584.
270.
160.
0625
1.72
40.2
890
1.92
0.01
00.
195
594.
420.
150.
1041
3.28
61.9
996
3.91
0.01
50.
21
604.
570.
150.
0534
9.42
52.4
110
16.3
20.
008
0.21
861
4.72
0.15
0.06
323.
6148
.54
1064
.86
0.00
90.
227
634.
880.
160.
0522
1.82
35.4
911
00.3
50.
008
0.23
5
645.
030.
150.
0312
0.40
18.0
611
18.4
10.
005
0.24
655.
180.
150.
0414
1.97
21.3
011
39.7
10.
006
0.24
6
WF
1
Sam
ple
No.
Sam
ple
Dep
th(m
)S
ampl
e In
terv
alLe
ngth
(m)
Moi
stur
eC
onte
nt(C
u. r
n/cu
. m)
Cl i
nS
oil W
ater
(g/c
u. m
)
Cl I
nS
oil W
ater
(9/s
q . m
)
Cum
. CI
in S
oil W
ater
(g/s
q. m
)
Vol
. Wat
erC
onte
nt(m
)
Cum
. Vol
.W
ater
Con
tent
(m)
66 67 68 69 70 71 72 73 74 75 77 79 81 82 83 84 85 86
5.33
5.49
5.64
5.94
6.25
8.40
6.55
6.71
7.16
7.47
10.2
113
.26
13.7
214
.02
14.3
314
.57
14.7
815
.09
0.15
0.16
0.15
0.30
0.31
0.15
0.15
0.16
0.45
0.31
2.74
3.05
0.46
0.30
0.31
0.24
0.21
0.31
0.10
0.04
0.10
0.11
0.12
0.15
0.08
0.10
0.11
0.05
0.01
0.12
0.08
0.11
0.11
0.10
0.09
0.11
329.
8116
9.27
325.
2344
1.69
528.
0160
1.08
277.
3532
9.85
696.
1315
2.46
7.76
15.5
63.
894.
414.
464.
583.
994.
96
49.4
727
.08
48.7
813
2.51
163.
6890
.16
41.6
052
.78
268.
2647
.26
21.2
747
.46
1.79
1.32
1.45
1.10
0.84
1.54
1189
.18
1216
.26
1265
.04
1397
.55
1561
.23
1651
.39
1692
.99
1745
.77
2014
.03
2061
.29
2082
.56
2130
.02
2131
.81
2133
.30
2134
.58
2135
.68
2136
.52
2138
.06
0.01
50.
006
0.01
50.
033
0.03
70.
023
0.01
20.
016
0.05
00.
016
0.02
70.
366
0.03
70.
033
0.03
40.
024
..019
0.03
4
0.26
10.
267
0.28
20.
315
0.35
20.
375
0.38
70.
403
0.45
30.
479
0.50
60.
872
0.90
90.
942
0.97
61.
001.
019
1.05
3
WF
2
Sam
ple
No.
Sam
ple
Dep
th S
ampl
e In
terv
alM
oist
ure
Cl I
nC
l in
Cum
. CI
Vol
Wat
erC
um. V
ol.
(m)
Leng
thC
onte
ntS
oil W
ater
Soi
l Wat
erIn
Soi
l Wat
erC
onte
ntW
ater
Con
tent
(m)
(Cu.
rn/
cu. m
)(9
/cu.
m)
(9/s
q. m
)(9
/sq.
m)
(m)
(m)
870.
000.
000.
054.
99o.
000.
000
0
880.
150.
150.
097.
971.
201.
200.
014
0.01
489
0.27
0.12
0.04
6.16
0.74
1.94
0.00
50.
019
910.
490.
220.
046.
441.
423.
360.
009
0.02
892
0.58
0.09
0.05
10.7
60.
974.
330.
005
0.03
393
2.59
2.01
0.03
81.6
016
4.01
168.
340.
060.
093
942.
740.
150.
0384
.81
12.7
218
1.06
0.00
50.
098
952.
900.
160.
0380
.85
12.9
419
4.00
0.00
50.
103
973.
080.
180.
0419
0.61
34.3
122
8.31
0.00
70.
11
983.
350.
270.
0716
2.56
43.8
927
2.20
0.01
90.
129
993.
510.
160.
0631
5.59
50.4
932
2.69
0.01
0.13
910
03.
660.
150.
1256
1.93
84.2
940
6.98
0.01
80.
157
101
3.81
0.15
0.05
267.
8540
.18
417.
160.
008
0.16
510
23.
960.
150.
0539
2.45
58.8
750
6.03
0.00
80.
173
104
4.11
0.15
0.09
425.
4963
.82
569.
850.
014
0.18
710
64.
420.
310.
0316
4.08
50.8
762
0.72
0.00
90.
196
107
4.57
0.15
0.02
108.
3616
.25
636.
970.
003
0.19
910
94.
880.
310.
0421
0.83
65.3
670
2.33
0.01
20.
211
110
5.49
0.61
0.02
110.
4767
.39
769.
720.
012
0.22
311
15.
940.
450.
0420
7.40
93.3
386
3.05
0.01
80.
241
113
6.55
0.61
0.04
220.
5113
4.51
997.
560.
024
0.26
511
47.
160.
610.
0272
.04
43.9
710
41.5
30.
012
0.27
711
67.
770.
610.
0412
8.87
78.6
111
20.1
40.
024
0.30
1
118
8.69
0.92
0.03
57.0
952
.53
1172
.67
0.02
80.
329
120
9.30
0.61
0.03
38.0
623
.21
1195
.88
0.01
80.
347
123
9.60
0.30
0.08
91.8
227
.54
1223
.42
0.02
40.
371
126
10.1
80.
580.
1199
.45
57.6
812
81.1
00.
064
0.43
512
710
.70
0.52
0.07
56.5
229
.39
1310
.49
0.03
60.
471
130
11.7
41.
040.
0939
.19
40.7
613
51.2
50.
094
0.56
513
312
.65
0.91
0.06
21.2
019
.29
1370
.54
0.05
50.
6213
613
.44
0.79
0.18
21.8
517
.26
1387
.80
0.14
20.
762
139
14.0
20.
580.
012.
041.
1813
88.9
80.
006
0.76
814
016
.31
2.29
0.03
11.6
026
.56
1415
.54
0.06
90.
837
145
17.3
71.
060.
044.
084.
3214
19.8
60.
042
0.87
914
718
.75
1.38
0.11
5.05
6.97
1426
.83
0.15
21.
031
149
19.3
60.
610.
064.
672.
8514
29.6
80.
037
1.06
815
119
.51
0.15
0.07
4.40
0.66
1430
.34
0.01
11.
079
153
20.1
20.
610.
074.
682.
8514
33.1
90.
043
1.12
2
WF
3
Sam
ple
No.
Sam
ple
Dep
th(m
)S
ampl
e In
terv
alLe
ngth
(m)
Moi
stur
eC
onte
nt(C
u. r
n/cu
. m)
Cl I
nS
oil W
ater
(g/c
u. m
)
Cl I
nS
oil W
ater
(g/s
q. r
n)
Cum
. Cl
in S
oil W
ater
(g/s
q. m
)
Vol
. Wat
erC
onte
nt(m
)
Cum
. Vol
.W
ater
Con
tent
(m)
154
0.00
0.00
0.01
5.88
0.00
0.00
0.00
0.00
155
0.15
0.15
0.10
9.67
1.45
1.45
0.01
50.
015
156
0.24
0.09
0.10
36.1
63.
524.
700.
009
0.02
4
157
1.07
0.83
0.06
381.
1831
6.38
321.
080.
050.
074
158
1.19
0.12
0.05
294.
7835
.37
356.
450.
006
0.08
159
1.28
0.09
0.05
312.
8528
.16
384.
610.
005
0.08
516
01.
830.
180.
0317
2.38
31.0
341
5.64
0.00
50.
0916
22.
010.
180.
0423
3.51
42.0
345
7.67
0.00
70.
097
164
2.20
0.19
0.04
248.
4647
.21
504.
880.
008
0.10
5
165
2.59
0.39
0.06
374.
3414
5.99
650.
870.
023
0.12
8
166
2.74
0.15
0.10
634.
3495
.15
746.
020.
015
0.14
3
167
2.90
0.16
0.18
1018
.55
162.
9790
8.99
0.02
90.
162
169
3.11
0.21
0.27
1563
.85
328.
4112
37.4
00.
057
0.21
917
03.
360.
240.
0420
3.65
48.8
812
86.2
80.
010.
229
172
3.66
0.31
0.07
257.
1679
.72
1366
.00
0.02
20.
251
174
3.96
0.30
0.16
441.
9713
2.59
1498
.59
0.04
80.
299
178
4.57
0.61
0.21
370.
6122
6.07
1724
.66
0.12
80.
427
179
4.88
0.31
0.08
151.
3346
.91
1771
.57
0.02
50.
452
180
5.18
0.30
0.07
98.9
129
.67
1801
.24
0.02
10.
473
181
6.40
0.22
0.07
83.6
118
.40
1819
.64
0.01
50.
488
182
5.64
0.24
0.07
70.8
817
.01
1836
.65
0.01
70.
505
183
5.94
0.30
0.13
93.0
127
.90
1864
.55
0.03
90.
544
184
6.40
0.46
0.04
24.4
711
.26
1875
.81
0.01
80.
562
185
6.71
0.31
0.02
23.8
27.
3818
83.1
90.
006
0.56
818
87.
160.
450.
0421
.24
9.56
1892
.75
0.01
80.
586
189
7.47
0.31
0.03
3.90
1.21
1893
.96
0.00
90.
595
190
7.71
0.24
0.03
3.42
0.82
1894
.78
0.00
70.
602
191
7.93
0.22
0.17
6.98
1.53
1896
.31
0.03
70.
639
193
8.38
0.45
0.17
6.28
2.83
1899
.14
0.07
70.
716
196
9.14
0.76
0.09
4.99
3.80
1902
.94
0.06
80.
784
198
9.60
0.46
0.11
5.13
2.36
1905
.30
0.05
10.
835
199
9.91
0.31
0.05
4.80
1.49
1906
.79
0.01
60.
851
201
10.3
60.
450.
106.
142.
7619
09.5
50.
045
0.89
620
310
.97
0.61
0.05
4.00
2.44
1911
.99
0.03
10.
927
204
11.2
80.
310.
064.
821.
5019
13.4
90.
019
0.94
6
Sam
ple
No.
Sam
ple
Dep
th(m
)S
ampl
e In
terv
alLe
ngth
(m)
WF
4
Moi
stur
eC
l in
Con
lent
Soi
l Wat
er(C
u. r
n/cu
. m)
(9/c
u. m
)
Cl i
nS
oil W
ater
(g/s
q. m
)
Cum
. CI
in S
oil W
ater
(gis
q. m
)
Vol
. Wat
erC
onte
nt(m
)
Cum
. Vol
.W
ater
Con
tent
(m)
218
0.00
0.00
0.01
8.89
0.00
0.00
0.00
0.00
219
0.09
0.09
0.04
8.80
0.79
0.79
0.00
40.
004
222
0.37
0.28
0.15
101.
2828
.35
29.1
40.
042
0.04
6
223
0.46
0.09
0.13
204.
6418
.42
47.5
60.
012
0.05
8
224
0.55
0.09
0.08
295.
0426
.55
74.1
10.
007
0.06
5
225
0.64
0.09
0.10
524.
4147
.20
121.
310.
009
0.07
4
227
0.73
0.09
0.18
483.
3743
.50
164.
810.
016
0.09
228
0.91
0.18
0.03
79.9
114
.38
179.
190.
005
0.09
5
229
1.22
0.31
0.05
189.
2258
.66
237.
850.
016
0.11
1
230
1.31
0.09
0.04
165.
8414
.93
252.
780.
004
0.11
5
231
1.40
0.09
0.03
96.7
48.
7126
1.49
0.00
30.
118
232
1.49
0.09
0.03
170.
4315
.34
276.
830.
003
0.12
1
233
1.58
0.09
0.02
138.
8612
.50
289.
330.
002
0.12
3
234
1.71
0.13
0.02
169.
2222
.00
311.
330.
003
0.12
6
235
1.80
0.09
0.05
469.
0642
.22
353.
550.
005
0.13
1
236
2.23
0.43
0.06
509.
5121
9.09
572.
640.
026
0.15
7
237
2.41
0.18
0.05
418.
9475
.41
648.
050.
009
0.16
6
238
2.90
0.49
0.03
257.
2512
6.05
774.
100.
015
0.18
1
239
3.05
0.15
0.04
352.
9152
.94
827.
040.
006
0.18
7
240
3.20
0.15
0.04
358.
2453
.74
880.
780.
006
0.19
3
241
3.35
0.15
0.03
246.
9137
.04
917.
820.
005
0.19
8
242
3.90
0.55
0.03
209.
7211
5.35
1033
.17
0.01
70.
215
243
4.27
0.37
0.09
780.
9828
8.96
1322
.13
0.03
30.
248
244
4.88
0.61
0.04
339.
3120
6.98
1529
.11
0.02
40.
272
245
5.47
0.59
0.04
228.
5113
4.82
1663
.93
0.02
40.
296
246
5.79
0.32
0.04
236.
2975
.61
1739
.54
0.01
30.
309
WF
5
sam
ple
No.
Sam
ple
Dep
th(m
)S
ampl
e In
terv
alLe
ngth
(m)
Moi
stur
eC
onte
nt(C
u. r
n/cu
. m)
Ci I
nS
oil W
ater
(9/c
u. m
)
Cl I
nS
oil W
ater
(g/s
q. m
)
Gum
. CI
In S
oil W
ater
(g/s
q. m
)
Vol
. Wat
erC
onte
nt(m
)
Cum
. Vol
.W
ater
Con
tent
(m)
305
11.8
90.
760.
0419
.23
14.6
233
6.79
0.03
0.58
306
12.1
90.
300.
039.
912.
9733
9.76
0.00
90.
589
308
12.6
50.
460.
0311
.40
5.24
345.
000.
014
0.60
331
013
.26
0.61
0.03
14.3
08.
7235
3.72
0.01
80.
62 1
312
13.8
70.
610.
0524
.49
14.9
436
8.66
0.03
10.
652
314
14.3
30.
460.
0414
.72
6.77
375.
430.
018
0.67
315
14.6
30.
300.
0619
.69
5.91
381.
340.
018
0.68
831
715
.24
0.61
0.06
21.1
012
.87
394.
210.
037
0.72
531
915
.85
0.61
0.06
18.9
411
.55
405.
760.
037
0.76
232
217
.07
1.22
0.05
12.0
914
.75
420.
510.
061
0.82
332
317
.98
0.91
0.07
19.9
018
.11
438.
620.
064
0.88
732
518
.59
0.61
0.06
14.8
69.
0644
7.68
0.03
70.
914
326
18.8
10.
220.
0411
.54
2.54
450.
220.
009
0.92
3
WF
5
Sam
ple
No.
Sam
ple
Dep
thS
ampl
e In
terv
alM
oist
ure
Ci i
nC
l In
Cum
. Ci
Vol
. Wat
erC
um. V
ol.
(m)
Leng
thC
onte
ntS
oil W
ater
Soi
l Wat
erin
Soi
l Wat
erC
onte
ntW
ater
Con
tent
(m)
(Cu.
rn/
cu. m
)(9
/cu.
m)
(g/s
q. m
)(g
/sq.
m)
(m)
(m)
246
0.00
0.00
0.01
4.76
0.00
0.00
0.00
0.00
247
0.09
0.09
0.03
6.41
0.58
0.58
0.00
30.
006
248
0.18
0.09
0.03
4.49
0.40
0.98
0.00
30.
006
249
0.27
0.09
0.04
4.62
0.42
1.40
0.00
40.
0125
00.
370.
100.
034.
350.
441.
840.
003
0.01
325
20.
550.
180.
036.
341.
142.
980.
005
0.01
825
30.
640.
090.
024.
620.
423.
400.
002
0.02
254
0.73
0.09
0.03
4.23
0.38
3.78
0.00
30.
023
255
0.82
0.09
0.03
5.40
0.49
4.27
0.00
30.
026
256
0.91
0.09
0.02
6.32
0.57
4.84
0.00
20.
028
258
1.10
0.19
0.02
34.7
46.
6011
.44
0.00
40.
032
260
1.37
0.27
0.02
17.6
44.
7616
.20
0.00
50.
037
262
1.55
0.18
0.03
27.2
24.
9021
.10
0.00
50.
042
264
1.74
0.19
0.04
28.9
85.
5126
.61
0.00
80.
0526
61.
920.
180.
0317
.47
3.15
29.7
60.
005
0.05
526
72.
130.
210.
0210
.04
2.11
31.8
70.
004
0.05
926
82.
290.
160.
028.
871.
4233
.29
0.00
30.
062
270
2.47
0.18
0.03
12.0
92.
1835
.47
0.00
50.
067
273
2.74
0.27
0.05
15.6
64.
2339
.70
0.01
40.
081
275
3.05
0.31
0.03
14.1
74.
3944
.09
0.00
90.
0927
73.
350.
300.
0312
.60
3.78
47.8
70.
009
0.09
927
83.
510.
160.
0313
.93
2.23
50.1
00.
005
0.10
428
03.
810.
300.
0315
.36
4.61
54.7
10.
009
0.11
328
24.
270.
460.
0422
.08
10.1
664
.87
0.01
80.
131
283
4.42
0.15
0.08
47.2
17.
0871
.95
0.01
20.
143
285
4.88
0.46
0.10
70.1
632
.27
104.
220.
046
0.18
928
65.
180.
300.
0868
.25
20.4
712
4.69
0.02
40.
213
287
5.79
0.61
0.05
33.1
820
.24
144.
930.
031
0.24
428
96.
400.
610.
0843
.06
26.2
717
1.20
0.04
90.
293
290
6.71
0.31
0.04
25.8
38.
0117
9.21
0.01
20.
305
292
7.22
0.51
0.04
20.4
710
.44
189.
650.
020.
325
293
8.08
0.86
0.04
22.6
119
.45
209.
100.
034
0.35
929
58.
840.
760.
0430
.59
23.2
523
2.35
0.03
0.38
929
79.
450.
610.
0524
.56
14.9
824
7.33
0.03
10.
4229
89.
750.
300.
1049
.24
14.7
726
2.10
0.03
0.45
300
10.3
60.
610.
0429
.65
18.0
928
0.19
0.02
40.
474
302
10.9
70.
610.
1154
.14
33.0
331
3.22
0.06
70.
541
303
11.1
30.
160.
1255
.91
8.95
322.
170.
019
0.56
WF
7
Sam
ple
No.
Sam
ple
Dep
th(m
)S
ampl
e In
terv
alLe
ngth
(m)
Moi
stur
eC
onte
nt(C
u. r
n/cu
. m)
CI I
nS
oil W
ater
(g/c
u. m
)
Cl i
nS
oil W
ater
(g/s
q. m
)
Gum
. CI
in S
oIl W
ater
(g/s
q. m
)
Vol
. Wat
erC
onte
nt(m
)
Gum
. Vol
.W
ater
Con
tent
(m)
331
0.00
0.00
0.06
5.56
0.00
0.00
0.00
0.00
332
0.15
0.15
0.04
5.24
0.79
0.79
0.00
60.
006
333
0.24
0.09
0.05
4.17
0.38
1.17
0.00
50.
011
335
0.46
0.22
0.09
5.87
1.29
2.46
0.02
0.03
1
336
0.55
0.09
0.12
7.50
0.67
3.13
0.01
10.
042
337
0.64
0.09
0.13
8.43
0.76
3.89
0.01
20.
054
338
0.73
0.09
0.12
6.59
0.59
4.48
0.01
10.
065
339
0.88
0.15
0.13
7.64
1.15
5.63
0.02
0.08
5
340
0.91
0.03
0.17
8.18
0.25
5.88
0.00
50.
09
341
1.07
0.16
0.19
12.1
81.
957.
830.
030.
12
342
1.16
0.09
0.14
18.8
11.
699.
520.
013
0.13
3
343
1.37
0.21
0.10
10.2
32.
1511
.67
0.02
10.
154
344
1.46
0.09
0.06
8.69
0.78
12.4
50.
005
0.15
9
345
1.59
0.13
0.12
12.8
41.
6714
.12
0.01
60.
175
347
2.13
0.54
0.11
11.4
86.
2020
.32
0.05
90.
234
351
2.59
0.46
0.11
52.3
48.
9029
.22
0.05
10.
285
355
3.08
0.49
0.03
42.1
520
.65
49.8
70.
015
0.30
356
3.35
0.27
0.13
27.5
57.
4457
.31
0.03
50.
335
361
4.12
0.77
0.12
66.1
650
.95
108.
260.
092
0.42
736
25.
331.
210.
1044
4.76
538.
1664
6.42
0.12
10.
548
364
5.64
0.31
0.03
136.
5842
.34
688.
760.
009
0.55
7
365
5.79
0.15
0.04
176.
9926
.55
715.
310.
006
0.56
3
APPENDIX 7
CHLORIDE VS. DEPTH AND MOISTURE VS. DEPTH PROFILESWHISKY FLAT, NEVADA
69
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CHAPTER 3
COMPARISON OP RECHARGE RATES CALCULATED USING CHLORIDE MASSBALANCE VERSUS DETAILED SOIL-MOISTURE AND CLIMATIC DATA
BEATTY, NEVADA
TABLE OF CONTENTS
Page
ABSTRACT 1
INTRODUCTION 2
REGIONAL SETTING 2
METHODS 5
DRILLING AND LAB PROCEDURES 5
CHLORIDE MASS BALANCE METHOD 6
RESULTS 6
DISCUSSION 6
MODERN ROOT AND PERCOLATION DEPTHS 6
PAST ROOT AND PERCOLATION DEPTHS 8
SUBSURFACE FLOW ALONG A LESS PERMEABLE BOUNDARY 11
GROUNDWATER RECHARGE RATES AND GEOMORPHIC-SURFACE AGE 12
CONCLUSIONS 14
REFERENCES 16
APPENDICES 20
ABSTRACT
The chloride mass-balance approach for determining long-term groundwater
recharge rates was applied at a study site near Beatty, Nevada, and results
compared with an earlier study using detailed soil-moisture and climatic data.
Recharge rates calculated using the chloride method are 0.06-0.4 mm/year. This
range is based on the average of chloride concentrations at 9.14 and 9.37 m because
values never reached a steady state. Concentrations decrease to less than 150 mg/L
below this zone and are interpreted as reflecting chloride incorporated in the
sediments during deposition, and indicate the absence of recharge below 9-10 m.
The rate calculated from the earlier study was 0.04 mm/yr below 10 m. Though
the rates estimated are similar, the interpretations differ due to the method used.
The earlier study used a simplified, transient unsaturated-flow analysis while the
chloride conclusions are based on a physical record of the system's response to.
climatic and vegetative change. The high chloride concentration zone from 1.75-4.5
m is interpreted as reflecting the maximum root depth during the Pleistocene. The
intermediate chloride zone from 4.5-7.7 in is interpreted as recording the maximum
percolation depth during this time. The difference between these two depths may
reflect the lag between the increase In effective precipitation and the subsequent
change rooting depths and transpiration demands which would capture the water and
concentrate the chloride at shallower depths.
1
INTRODUCTION
Recent studies comparing recharge rates calculated using chloride mass balance
with Chlorine-36 (Phillips and Stone, 1985), tritium (Allison and Hughes, 1978;
Edmunds et aL, 1988), and tritium, oxygen-18, and deuteriun (Allison et al., 1985;
Stone, 1986) show similar results. This study compares recharge rates calculated
using chloride mass balance with estimates determined by the U.S. Geological Survey
using detailed climatic and soil-moisture data for a site near Beatty, Nevada
(Figure 1).
REGIONAL SETTING
The Beatty drill site was selected by the U. S. Geological Survey as part of
their ongoing study to determine recharge potential in arid environments (Nichols,
1986). The site is located 17 km southeast of Beatty and 30 km northwest of
Lathrop Wells, in the extreme northern edge of the Amargosa Desert. The elevation
is 847 m above mean sea level, and 158 m lower than the Beatty weather station, and
190 in higher than the Lathrop Wells station. Mean annual precipitation averages 74
mm at Lathrop Wells (Nichols, 1986) and 114 mm at Beatty, but with considerable
annual variation (National Oceanic and Atmospheric Administration, 1971). Seventy-
three percent of the precipitation occurs from November to April. Surface runoff
is rare (Nichols, 1986) though occasionally the Amargosa River has been flooded
(National Oceanic and Atmospheric Administration, 1971). Mean monthly temperatures
range from 5.2° C in January to 27.3° C in July. Prevailing winds are probably
similar to those in Las Vegas which are west to southwest (Houghton et al., 1975).
The study site (Figure 2) is bordered on the north by Tertiary volcanics, and
on the east by Precambrian-Cambrian quartzites and Paleozoic carbonates (Cornwall,
2
32
122 120
410
CALIFO
0
300KM
I I I
£ STUDY SITES
fl9GREAT BASIN DESERT
3
116
RNIA
NEVADA
ISIERRANEVEDA
112
ARIZONA
MOJAVE DESERT
Figure 1. Location of study .area (modified from Spaulding et al., 1983).
A 44 44 4 p4p L
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TERTIARY- QUATERNARYVOLCANICS
0
CAMBRIAN-DEVON I ANCARBONATES
CAMBRIAN- PALEOZO ICQUARTZ ITES
Q DRILL SITE
Figure 2. Generalized geology surrounding the Beatty drill site (modified
from Cornwall, 1972).
4
1972). The basin fill in the Amargosa Desert consists of unconsolidated to weakly
indurated, poorly stratified gravelly or silty sand, sandy graveL and thick beds
of clayey deposits of Tertiary and Quaternary age (Nichols, 1986). Some
Pleistocene and Holocene deposits occur locally. Desert pavement surrounding the
drill site is well-developed and extensive. Two large playas occur in the
vicinity, one 50 km to the southeast along the same orientation as the Amargosa
Desert, and the other about 40 km to the northwest. Nichols (1986) reports a
water table 86 m deep (Walker and Eakin, 1963) near the site. A water-level
sounding taken in the summer of 1986 measured 96 m. Vegetation Is creosote.
METHODS
DRILLING AND LAB PROCEDURES
Beatty core was drilled dry with an Odex drilling system, and samples were
weighed In the field Immediately. Comparison of field moisture contents with
psychrometer data of Fischer (writ. comm., 1987) indicates very little water loss
during sample recovery. Sampling was infrequent, but was enough to define the
chloride peak.
An average bulk density of 2.04 g/cc was calculated from eleven samples
collected at Beatty (Fischer, writ. comm. 1987), and was used to calculate chloride
concentrations and volumetric water contents (Appendix 1). Fischer suggests that
compaction during sampling or the high percentage of limestone and rhyolite may be
responsible for the high bulk density. More recent data suggests a value closer to
1.8 g/cc (Fischer, oral comm., 1988).
5
CHLORIDE MASS-BALANCE METHOD
Groundwater recharge rates and minimum .geomorphic-surface ages were calculated
using the chloride mass-balance method. For discussion of the method see Chapter
2.
RESULTS
The Beatty profile (Figure 3) shows a 4.4 m thick zone of high chloride, with
values greater than 2500 mg/L. Concentrations decrease with depth below this zone,
but remain greater than 1000 mg/L until 7.7 m. Values decrease again, but remain
above IOU mg/L as deep as 10.7 in. Moisture content averages 11% from 2.5 to 7.7 m
and 6% above and below this interval. Moisture contents and chloride
concentrations for each point are listed in Appendix 2. Cumulative chloride and
cumulative water values are listed in Appendix 3.
DISCUSSION
MODERN ROOT AND PERCOLATION DEPTHS
Coarse gravels make up most of the core below the top 0.6 in silt horizon
(Nichols, 1986). Creosote (Larrea tridentata) is the sole vegetation around the
site. Its roots are generally shallow, less than 1.7 in even in the absence of a
calcareous layer (Barbour et aL, 1977a), and the majority of roots appear to be
confined to the upper 0.1-0.45 in (Barbour et al., 1977b). According to a summary
study by Foxx et al. (1984) which looked at environmental and biological factors
controlling 1034 referenced root depths, 75% of the specimens recorded in
evaporative region 1 (Beatty) should root to 0.9 m or less.
6
0.00
0 5 20
0.10
0.20
BT
2a
0
2525
Figure 3.
Moisture piofi1e and chloride profile for the Beatty drill site.
3000
6000
II
II
I
Moi
stur
e co
nten
t (cu
. rn/
cu. m
)C
hlor
ide
conc
entr
atio
n (r
ng/L
)
Shallow evapotranspiration (ET) depths are supported by a chlorine-36 pulse
which occurs 0.5 m deep at the Nevada Test Site (Glfford, 1985), 90 km south of
Beatty, and neutron log readings taken at the Beatty site from January through
April 1987 (Fischer, writ. comm., 1987). The logs showed no change in the soil-
water contents despite the occurrence of three closely spaced storm events:
February 23-25 (6.1 mm), March 5-7 (9.1 mm), and March 15 (23 mm). The modern ET
zone appears to be confined to the upper 1 m.
PAST ROOT AND PERCOLATION DEPTHS
Reconstruction of Southwest Pleistocene climate indicates changes in effective
precipitation (precipitation - evaporation) over the past 18,000-21,000 years. This
change was accompanied by changes in basin vegetation types (Spaulding et al.,
1983). The absolute magnitudes of the temperature and precipitation change is
still debated. However, what is important for this study Is the net effect of
those changes on recharge rates, and rooting and percolation depths.
Available climatic data for southern Nevada is plotted qualitatively in Figure 4a
and the location of references' sites shown In Figure 4b. Data from south-central
Nevada is included to provide a more regional perspective. Mifflin and Wheat
(1979) data was not included on the diagram because it was impossible to equate
their relative ages to an absolute time scale.
Figure 4a shows unanimous agreement regarding an increase In effective
precipitation in the Southwest from 21,000-15,000 BP. The changes, however, appear
to be due to lower temperatures throughout the western Great Basin province, rather
than increased precipitation falling directly on the basin floor (Mifflin and
Wheat, 1979; Dohrenwend, 1984; Benson and Thompson, 1987). MifflIn and Wheat
(1979) concluded that the full-glacial climate in south-central and southern
8
0
0
4-0
SO-4ERN AC0
SOLITH-CENTRAL NEVADA
9
GEMCPI,lC SURFACESSOIL APACTERISTICS, 8 _____.r-----LAKE LEVEL--- WELLS..I,L 987
SE DIME N 0 LOGIC ALCHARACTERISTICS AMOLLUSCS
PACK RAT MIDOENS
SPAULOING.r *1., 984
PACK PAT MIDOENS
SPAULOINQ A AUMUCH, 1981
MIVATION
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THOMPSON S ME 40.982
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I SPAULDING,.t5I.. 1983
GL3.I. CLIMATICMODELS (3O-6ON)
I
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LAKE LEVELS
DAVIES J. 982
LAKE LEVELS
I 8ENSON A THOMPSON 987
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KUTZAACII S GIJETTER. 1981
PACK PAT MID0NS
THOMPSON 984
0 5 20 5
yEARS EF0RE PRESENT xI0')
Figure 4a. Qualitative summary of relative changes in Precipitation -Evaporation (P-E) estimated from 30,000 years ago to present.(+) Indicates values greater than present; (-) indicates valuesless than present; and (0) indicates present values. Source isnoted in right corner, data set in upper left corner.
-37°N
36°N
SIERRANEVADA
MONOLAKE
O 00 200 3001(1 LOME It RS
OWENSLAKE
SEARLESLAKE
LAKELAHON TAN
WALKER GATECLIFFLAKE £SHELTER
£WHISKY FLAT
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MANLYLAKE
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cBLAKE
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' \OMOHAVI
I
.
360tT
a STUDY SITE2-8 KYR AREAS OFDESERT SCRUB
12-8 KYR AREAS OFNOODLAND
Figure 4b. Location of areas for which paleoclimatic information isavailable (modified from Smith and Street-Perrott, 1983).
10
Nevadan basins was actually more arid than present. This is supported by recent
sedimentological work by Quade (1986) in the Las Vegas Valley. The paleoecology of
the Southwest suggests, at most, only a small increase in average annual
precipitation (Spaulding et al., 1983).
15,000-8,000 yrs liP appears to be a period of transition. Effective
precipitation continues to be greater than present until about 8,000 yrs lip, but
the trend is towards drier conditions. The only exception to this trend noted in
Figure 4a is in Kutzbach and Guetter (1986) climatic analysis for the northern-
middle latitudes (30-60 N). This is attributed to their use of a global scale
compared to the other, more local analyses (Spaulding and Graumlich, 1986).
Information, for the last 10,000 years, is scarce and somewhat conflicting. Modern
conditions, however, appear to have been achieved about 8,000 BP.
Chloride concentrations are greater than 3000 mg/L from 1.75-4.4 m below land
surface and between 1000 to 2000 mg/L from 4.5-7.7 in. The modern ET zone estimate
of 1.0 a cannot account for this thickness. I suggest that the lower, moderately
high zone represents the maximum percolation depth during the Pleistocene and the
upper, higher chloride zone represents the maximum root depth during this time.
The difference between these two depths may be due to the lag between the increase
in effective precipitation and thus deep percolation, and the subsequent change in
vegetation type and transpiration demands which could now capture the water and
concentrate the chloride at shallower depths.
SUBSURFACE FLOW ALONG A LESS PERMEABLE BOUNDARY
The moisture content for the interval from 2.5-7.5 m is 11 % versus 6% for the
zones above and below it (Figure 3). Work done by Gifford (1985) at the Nevada
Test Site shows that downslope, subsurface flow of water along an impermeable layer
11
can leach chloride from the lower portion of the soil profile. No distinctive
impermeable zones were encountered at Beatty during drilling, but the stratified
nature of alluvial fans creates local, less permeable horizons. The higher
moisture content may also be due to grain-size variation. No sieve analyses were
done on the Beatty samples.
GROUNDWATER RECHARGE RATES AND GEOMORPHIC-SURFACE AGES
Groundwater recharge calculations use the average chloride concentration below
the root zone provided it has reached a steady-state. The concentrations in this
steady state zone may represent primary chloride (deposited with the sediments),
secondary chloride (added after deposition by infiltrating waters), or leached
chloride values due to subsurface flow. Only secondary chloride values represent
recharge. However, determining if the concentrations are primary or secondary can
be difficult. Information on soluble chloride concentrations for different
lithologies is minimal, what exists has a considerable range, and the source of the
chloride in the unweathered rock is unclear. Recorded water-soluble chloride
values for limestone range from 10-110 mg/L, and 86-3970 mg/L (mean value of 907
mg/L) for dolomites (Wedepohi et al., 1969). No analysis was made of the amount of
soluble chloride present in the carbonates that make up the Beatty alluvium, but
chloride values decrease to 124 mg/L at 10.59 m.
A long-term precipitation range of 50-175 mm/year and a chloride input range
of 0.5-1.0 mg/L were used in the recharge and age calculations. The chloride range
incorporated data from East Stewart and Kawich Creeks, two very narrow mountain
valleys (McKinley, writ. comm., 1986), and the Nevada Test Site (Gifford, 1985).
The range would be too high if oceanic chloride was the sole source of chloride at
Beatty. However two large playas occur in the vicinity and make it reasonable to
12
assume higher concentrations.
The drill hole is 10.7 in deep. If the last two values collected at 10.59 and
10.74 m deep, are taken as representing the beginning of the steady-state zone, and
the 134 mg/L average is assumed to represent secondary chloride, then long-term
recharge is 0.19-1.3 mm/yr. This range, however, Is higher than the 0.04-0.8 mm/yr
range calculated for the less arid Whisky Flat (Fouty, 1989b). If the chloride
concentration in the soil water is determined from samples collected at 9.14 and
9.37 in then the average is 427.5 ing/L. Recharge rates calculated using this value
range from 0.06 to 0.4 mm/yr, and are similar to the 0.04 mm/yr estimated by
Nichols (1986) using climatic and soil-moisture data and a simplified analysis of
transient-unsaturated flow. Nichols, however, suggests that this 0.04 mm/yr occurs
below 10 in. Considering the lithologles of the alluvial sediments, limestone and
dolomite, I suggest that the 134 mg/L average chloride concentration for 10.59 and
10.7 m represents primary chloride, and that recharge is not occurring below 10 in.
Though the rates estimated are Similar, the Interpretation of the results
differs due to the method used. The earlier study used a simplified, transient-
unsaturated flow analysis while the chloride conclusions are based on actual data
which reflects the heterogeneities In the sediments and the physical record of the
system's response to climatic and vegetative change. The thick zone of high
chloride concentrations is interpreted as recording increased effective
precipitation during the Pleistocene. Neutron log readings taken in 1987 indicate
that modern percolation depths are confined to the near surface.
Age calculations are valid only for stable, non-aggrading geomorphic surface
(Fouty, 1989a). The Beatty surface appears stable based on the extensive desert
pavement and the configuration of the upper chloride zone. Age estimates range
from 9,148 to 64,040 years based on the amount of chloride accumulated in the upper
13
4.4 in. The wide range in years indicates that the precipitation and chloride input
ranges are too broad, and need to be narrowed. However, this is not currently
possible given the amount of paleoclimatic information available. The calculated
surface age thus contributes little in the way of a specific surface date, but the
estimate does suggest that recharge below 10 in has been minimal or nonexistent for
at least 6000 years.
CONCLUSIONS
Estimates of modern percolation and' root depths at Beatty indicate that the 4-
7 in thick high-chloride zone is not recording modern ET conditions. The
paleoclimatic reconstruction indicates an increase in effective precipitation and
changes in vegetation during the Pleistocene. Chloride concentrations are greater
than 3000 mg/L from 1.75 to 4.4 in below land surface and between 1000 to 2000 mg/L
from 4.5 to 7.7 in. As the modern ET zone estimate of 1.0 in cannot account for
these zones, the lower, moderately high zone represents the maximum percolation
depth during the Pleistocene and the upper, higher chloride zone represents the
maximum root depth during this time. The difference between these two depths may
be due to the lag between the increase in effective precipitation and thus deep
percolation, and the subsequent change in vegetation type and transpiration demands
which could now capture the water and concentrate the chloride at shallower depths.
Seven meters thus represents the long-term, deep percolation active zone.
Chloride concentrations decrease to 124 mg/L at 10.59 in but never reach a
steady state. This value is interpreted original chloride incorporated In with the
sediments during deposition. Recharge rates calculated from concentrations at 9.14
and 9.37 a are 0.06-0.4 mm/year and compare favorably with Nichols' (1986) estimate
14
of 0.04 mm/year below 10 in using detailed climatic and soil-moisture data and a
simplified analysis of transient-unsaturated flow. The difference In the
interpretation regarding recharge potential below 10 m is due to the method used.
If the thick zones of high chloride are interpreted as recording Pleistocene
conditions, then it is unlikely that recharge is occurring under the more arid
modern conditions.
15
REFERENCES
Allison, GB., and Hughes, M.W., 1978, The use of environmental chloride and
tritium to estimate total recharge to an unconfined aquifer: Australian
Journal of Soil Research, 16, 181-95.
Allison, G.B. and Hughes, MW., 1983. The use of natural tracers as
indicators of soil-water movement in a temperate semi-arid region: Journal
of Hydrology, 60, 157-173.
Allison, G.B.,Stone, W.J., Hughes, M.W., 1985, Recharge in karst and dune
elements of a semi-arid landscape as indicated by natural isotopes andchloride: Journal of Hydrology 76, 1-25.
Barbour, M.G., Cunningham, W.C., Oechel, W.C.,, and Bamberg, S.A., 1977a,
Growth and development, form and function In "Creosote Bush -- Biology and
chemistry of Larrea in New World deserts," (Mabry,T.J., Hanzlker,J.H., and
Difeo,D.R., Jr., Eds.). 48-91.
Barbour, M.G., MacMahon, J.A., Bamberg, S.A., and Ludwig, J.A., 1977b, The
structure and distribution of Larrea communities In "Creosote Bush--
Biology and chemistry of Larrea in New World deserts, (Mabry,T.J.,
Hanziker,J.H., and Difeo,D.R., Jr., Eds.), 227-251.
Benson L.V. and Thompson, R.S., 1987, Lake-level variation In the Lahontan
Basin for the past 50,000 years: Quaternary Research 28, 69-85.
Bouwer, H., 1980, Deep percolation and groundwater management: Proceedings of
the Deep Percolation Symposium, Scottsdale, AZ, Arizona Department of Water
Resources, 13-19.
Cornwall, H.R., 1972, Geological Map of Southern Nye County, Nevada: Nevada
Bureau of Mines Bulletin 77, Map scale: 1:250,000.
Davis, 3.0.,
Area: In
0' Connell,
1982.
1982, Bits and Pieces: The last 35,000 years in the Lahontan
Man and environment in the Great Basin, Madsen, B.B. and
J.F. (eds.), 53-75: Society for American Archeology Papers No. 2,
Davis, O.K. and Sellers, W.D., (in press). Contrasting climatic histories for
western North America during the late glacial and early Holocene In "Current
Research in the Pleistocene," Vol. 4.
Dohrenwend, J.S., 1984, Nivation landforms in the western Great Basin and
their paleoclimatic significance: Quaternary Research, 22, 275-288.
Edmunds, W.M., Darling, W.G., KInnIburgh, D.G., 1988, Solute profile
techniques for recharge estimation in semi-arid and arid terrain, In
Simmers, I. (Ed.), NATO ASI, Estimation of Natural Groundwater Recharge,
Series C: Mathematical and Physical Sciences Vol. 222: 139-157.
16
17
Fouty, S.C., 1989a, Chloride mass balance as a method for determininggroundwater recharge rates and alluvial surface ages, Whisky Flat andBeatty, Nevada (Chapter 1): M.S. thesis, University of Arizona, Tucson.
Fouty, S.C., 1989b, Chloride mass balance as a method for determininggroundwater recharge rates and alluvial surface ages, Whisky Flat andBeatty, Nevada (Chapter 2): M.S. thesis, University of Arizona, Tucson.
Foxx, T.S., Tierney, G.D., and Williams, J.M., 1984, Rooting depths of plantsrelative to biological and environmental factors: Los Alamos NationalLaboratory report LA-10254-MS.
Gif ford, S.K., III, 1985, Use of chloride and chlorine isotopes in theunsaturated zone to characterize recharge at the Nevada Test Site: M.S.thesis, University of Arizona.
Houghton, J.G., Sakamoto, C.M., and Gif ford, R.O., 1975, Nevada's Weather andClimate: Nevada Bureau of Mines and Geology, Special Publication 2.
Kutzbach, J.E. and Guetter, P.J., 1986, The influence of changing orbitalparameters and surface boundary conditions on climate simulations for thepast 18,000 years: Journal of the Atmospheric Sciences, Vol. 43, No. 16,
1726-1759.
Matthias, A.D., Hassan, H.M., Yu-Qi Hu, Watson, i.E., and Warrick, A.W.,1986, Evapotranspiration estimates derived from subsoil salinity data:Journal of Hydrology 85, 209-223.
McCord, J.T. and Stephens, D.B., 1987, Lateral moisture flow beneath a sandyhilislope without an apparent impeding layer: Hydrological Processes, Vol.1: 225-238.
McGurk, B.E. and Stone, W.J., 1985, Evaluation of laboratory procedures fordetermining soil-water chloride: New Mexico Bureau of Mines and MineralResources Open-File Report 215, 34p.
Miff un, M.D., and Wheat, M.M., 1979, Pluvial lakes and estimated pluvia].climates of Nevada: Nevada Bureau of Mines and Geology, Bull. 94, 57p.
National Oceanic and Atmospheric Administration-National Weather Service Incooperation with the University of Nevada, Reno, 1971. Climatography of theUnited States, No. 20-26, Climatological Summary (Beatty, Nevada, 1941-1970).
Nichols, W.D., 1986, Geohydrology of the unsaturated zone at burial site forlow-level radioactive waste near Beatty, Nye County, Nevada: U.S.Geological Survey Open-File Report 85-198, 85p.
Phillips, F.M. and Stone, W.J., 1985, Chemical considerations in ground-waterrecharge: Symposium: Water and Science Proceedings, New Mexico WaterResources Research Institute, Report 182, 109-126.
Quade, J., 1986, Late Quaternary environmental changes in the upper Las Vegas
Valley, Nevada: Quaternary Research 26, 340-357.
Smith, G.I. and Street-Perrott, F.A., 1983, Pluvial Lakes of the western
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19
APPENDIX 1
1
EQUATIONS USED IN THE COMPUTER PROGRAMS
CHLORIDE IN THE SOIL WATER (CLsw)
Clsw = [Cle X (Wtr added/Dry Wt)]/ ([(Wet Wt - Dry Wt) X fbi/DrY Wt)
Clsw = Chloride in soil water (mg/I)Cle = Chloride in the extract (ppm)Wtr added = Amount of dionized water added to sample (g)Dry Wt = Weight of oven dried sample (g)Wet Wt = Weight of sample and water (g)
= Bulk density (g/cu. cm)
2.04 g/cu. cm for Beatty
CUMULATIVE CHLORIDE (CC) AT A GIVEN DEPTH
CC = (Clsw X L)
CC = Cumulative chloride (g/sq. m.)L = Sample interval length (in)Clsw = Chloride in soil water (g/cu. in.)
VOLUMETRIC WATER CONTENT (Vwc)
Vwc = [(Wet Wt. - Dry Wt.) X b] / Dry Wt.
1Stone, 1986; written communication
20
APPENDIX 2CHLORIDE CONCENTRATION VALUES FOR BEATTY, NEVADA
BT2A
Sample No. Sample Depth Moisture Dry Wt. Wt. Wtr. CI in Cl in(m) Content Soil Added Extract Soil Water
(Cu. rn/cu. m) (gm) (gm) (ppm) (mg/I)
Bulk Density = 2.05 g/cu. cm (Fischer, U. S. Geological Survey, 1987, writ. comm.)
Note: Dry Wt. Soil = Weight of oven-dried soil used in salt extraction.Wt. Wtr. Added = Weight of deionized water in salt extraction.
Volumetric moisture contents are rounded to the nearest hundredthin the table, but Cl in Soil Water calculations are based on truevalue,
21
6A 0.69 0.05 53.47 80.33 7.20 239.105A 1.14 0.05 39.40 83.46 9.20 367.218A 1.75 0.04 46.43 90.38 68.00 3189.331 OA 2.29 0.05 50.40 80.58 140.00 4402.429A 2.51 0.10 47.86 82.99 205.00 3516.53
13A 3.05 0.12 43.60 82.99 210.00 3295.1212A 3.28 0.11 41.63 82.54 180.00 3339.821 1A 3.50 0.07 46.42 83.82 126.00 3219.91iSA 4.27 0.10 42.67 83.74 140.00 2776.1314A 4.42 0.09 43.19 93.50 123.00 2968.2518A 5.94 0.15 39.74 84.67 130.00 1870.8417A 6.55 0.15 44.17 81.52 155.00 1896.5320A 7.31 0.10 37.80 83.46 64.00 1439.5519A 7.77 0.10 45.58 83.10 66.00 1244.3821A 9.14 0.06 56.74 87.07 17.20 419.8522A 9.37 0.06 51.94 86.39 14.90 436.0524A 10.59 0.08 43.95 98.02 3.20 124.4023A 10.74 0.09 53.30 81.40 5.20 145.41
AP
PE
ND
IX 3
CU
MU
LAT
IVE
CH
LOR
IDE
VA
LUE
SF
OR
BE
AT
TY
, NE
VA
DA
BT
2A
Not
e:C
um..
Vol
. Wat
er C
onte
nt =
Cum
ulat
ive
volu
met
ric w
ater
cont
ent.
Cuu
i,Cl i
n S
oil .
Wat
er =
Cum
ulat
ive
chlo
ride
inso
il w
ater
.V
ol. W
ater
Con
tent
=V
olum
etric
wat
er c
onte
nt.
Bul
k D
ensi
ty2.
05 g
/cu.
cm
. (F
isch
er,
u.s.
Geo
logi
cal S
urve
y,19
87, w
rit. c
omm
.).
Sam
ple
No.
Sam
ple
Dep
th S
ampl
e In
terv
al(m
)Le
ngth
(m)
Moi
stur
eC
onte
nt(C
u. r
n/cu
. m)
Cl i
nS
oil W
ater
(g/c
u. m
)
Cl i
nS
oil W
ater
(gls
q.rn
)
Gum
. Cl
in S
oil W
ater
(g/s
q. m
)
Vol
. Wat
erG
um. V
ol.
Con
tent
Wat
er C
onte
nt
(m)
(m)
6A 5A 8A bA 9A 13A
12A
hA 15A
14A
18A
17A
20A
19A
21A
22A
24A
23A
0.69
1.14
1.75
2.29
2.51
3.05
3.28
3.50
4.27
4.42
5.94
6.55
7.31
7.77
9.14
9.37
10.5
910
.74
0.69
0.45
0.61
0.54
0.22
0.54
0.23
0.22
0.77
0.15
1.52
0.61
0.76
0.46
1.37
0.23
1.22
0.15
0.05
0.05
0.04
0.05
0.10
0.12
0.11
0.07
0.10
0.09
0.15
0.15
0.10
0.10
0.06
0.06
0.08
0.09
11.9
618
.36
127.
5722
0.12
351.
6539
5.41
367.
3822
5.39
277.
6126
7.14
280.
6328
4.48
143.
9612
4.44
25.1
926
.16
9.95
13.0
9
8.25
8.26
77.8
211
8.87
77.3
621
3.52
84.5
049
.59
213.
7640
.07
426.
5517
3.53
109.
4157
.24
34.5
16.
0212
.14
1.96
8.25
16.5
194
.33
213.
2029
0.56
504.
0658
8.58
638.
1785
1.93
892.
0013
18.5
514
92.0
816
01.4
916
58.7
316
93.2
416
99.2
617
11.4
017
13.3
6
0.03
50.
023
0.02
40.
027
0.02
20.
065
0.02
50.
015
0.07
70.
014
0.22
80.
092
0.07
60.
046
0.08
20.
014
0.09
80.
014
0.03
50.
058
0.08
20.
109
0.13
10.
196
0.22
10.
236
0.3
130.
327
0.55
50.
647
0.72
30.
769
0.85
1
0.86
50.
963
0.97
7