soil forming factors - missouri land improvement...

Water Movement in SoilsWater Movement in Soils

Clayton E. LeeRetired NRCS State Soil Scientist

Columbia, Missouri

1) Soil Forming Factors2) Primary Properties that affect Water

Movement in Soils3) Soil Water Concepts4) Where to get additional information

Today’s Talking PointsToday’s Talking Points

Parent Material

Climate

Topography

Biological Activity

Ti

Soil Forming FactorsSoil Forming Factors

Time

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Those that formed in place - residuum Those that have been transported - In

Missouri: transported by Ice, Water, Wind and Gravity

Two Categories of Parent Two Categories of Parent MaterialMaterial

Soil that form Soil that form in placein place from the from the weathering of the underlying weathering of the underlying rock or minerals is called rock or minerals is called

ResiduumResiduum

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Soil material moved by ice or glaciers is calledGlacial Till or Till

Glacial till material consists of mixtures of rocks, sand, silt, and claythat have traveled long distances.

Soil material that has been transported by water is called Alluvium

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Slow velocitySlow velocity flooding produces clayey soils.

High velocity flooding gproduces loamy soils.

Floods can move great

amounts of soil material.

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Wind deposited Wind deposited -- the the further from the source further from the source the the loess gets loess gets thinner and has more clay (less thinner and has more clay (less silt)silt)Thickest deposits are adjacent to the Missouri Thickest deposits are adjacent to the Missouri

LoessLoess

jjand Mississippi River flood plains.and Mississippi River flood plains.

Colluvium is material Colluvium is material transported down slope by transported down slope by gravity. gravity.

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Temperature and Moisture are major Temperature and Moisture are major influences. In the US, we have influences. In the US, we have permafrost in Alaska and very warm permafrost in Alaska and very warm conditions in our southern states. conditions in our southern states. With regard to moisture we have With regard to moisture we have With regard to moisture, we have With regard to moisture, we have both deserts and rain forests.both deserts and rain forests.

ClimateClimate

The configuration of the land surface◦ Slope gradient◦ Slope shape

TopographyTopography

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Plants Animals

BiotaBiota

Prairies generate huge amounts of Organic Matter

Makes thick dark

Surface Horizons

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Recent floods to “old” residuum

TimeTime

1) Soil Texture – particle size distribution2) Soil Structure3) Organic Matter Content4) Landform – hill slope profile

Primary Factors that influence Primary Factors that influence Water Movement through the Water Movement through the SoilSoil

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Particle Sizes

Sand: 2mm to .05mm

Silt: .05 mm to .002 mm

Clay: smaller than .002mm

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Blocky or granular - surface layer, A horizons

Platy or blocky - subsurface, E horizons if present

Blocky and/or Prismatic - subsoil, B horizons (compound: prismatic parting to blocky)

StructureStructure

Massive or Single grained -substratum, C horizons

Soil StructureSoil Structure

Soil Organic Matter Content higher levels:◦ Will increase the soils ability to store and give up water plants.◦ Will increase water movement rates through the soil.

Soil Organic MatterSoil Organic Matter

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How we can describe shapes of the land surface.

Slope shape and gradient are important considerations.

LandformsLandforms

In soil science, permeability is defined qualitatively as the ease with which gases, liquids, or plant roots penetrate or pass though a soil mass or layer. It is measured in length with no time component.

Saturated hydraulic conductivity is a quantitative measure of a saturated soil's ability to transmit water when subjected to a hydraulic gradient. It can be thought of as the ease with which pores of a saturated soil permit water movement. It is measured in both length and time.

Permeability classes and most references to permeability have been removed from the NSSH and replaced with the saturated

KsatKsatSaturated Hydraulic ConductivitySaturated Hydraulic Conductivity

been removed from the NSSH and replaced with the saturated hydraulic conductivity classes of the 1993 Soil Survey Manual.

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705.00 100.00 705.00 100.00

VERY HIGH141.14

VERY RAPID

20.00

100.00 14.17

14.11

MODERATELY RAPID 2.00

HIGH

1.417

SATURATED HYDRAULIC CONDUCTIVITY - PERM EABILITY

Permeability ClassKsat Class

10.00

RAPID

42.34 6.00

VERY LOW IMPERMEABLE0.00 0.00 0.00 0.00

μm/sec in/hr μm/sec in/hr

0.60

0.20

0.06

0.0015

μm/sec x 0.1417 = in/hr in/hr x 7.0572 = μm/sec

0.01

LOW

1.41

0.42

0.1417

0.01417

MODERATELY SLOW

SLOW

0.10

VERY SLOW

0.01

MODERATELY HIGH

MODERATELY LOW

#######

4.23

1.00

MODERATE

Saturated hydraulic conductivity is the amount of water that would move vertically through a unit area of saturated soil in unit time under unit hydraulic gradient.

If you find old permeability information If you find old permeability information, you can convert from um/sec to in/hr bymultiplying um/sec by .1417

Do you have an awareness of the factors of soil formation?

How about the primary factors that influence water movement through soil?

What is Saturated Hydraulic Conductivity? Ready to move on to Soil Water Concepts?

Quick ReviewQuick Review

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Does water moves through all soils at the same rate?

Soil horizons and restrictive features. Water tables. Interpretations: Hydraulic groups &

l

Soil Water ConceptsSoil Water Concepts

Drainage classes.

clay pans abrupt texture change discontinuities bedrock

Soil Horizons and Soil Horizons and Restrictive FeaturesRestrictive Features

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Clay PanSoils

Some have drastically different

i lmaterial underneath

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WATER TABLESWATER TABLES

PERCHED (on something in thesoil profile like)

fragipansclay pansabrupt texture changediscontinuities discontinuities bedrock

APPARENT (flood plains)from the bottom up

RedoxiRedoximorphmorphic ic FeaturesFeatures

The shapes and forms of bodies resulting from the

reduction and oxidation of iron

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Gray Redox Depletion

Describe Soil Colors

Soil Matrix Color

Reddish Redox Concentration

Hydrologic Groups (a) Definition Hydrologic group is a group of soils

having similar runoff potential under similar storm and cover conditions.

(b) Classes The soils in the United States are placed into four groups, A, B, C,

and D, and three dual classes, A/D, B/D, and C/D. In the definitions of the classes, infiltration rate is the rate at which water enters the soil at the surface and is controlled by the surface conditions. Transmission rate is the rate at which water moves in the soil and is controlled by soil properties. Definitions of the classes are as follows:

A. (Low runoff potential). The soils have a high infiltration rate even when thoroughly wetted. They chiefly consist of deep, well drained to excessively drained sands or gravels. They have a high rate of water transmission.

B. The soils have a moderate infiltration rate when thoroughly wetted. They chiefly are moderately deep to deep, moderately wetted. They chiefly are moderately deep to deep, moderately well drained to well drained soils that have moderately fine to moderately coarse textures. They have a moderate rate of water transmission.

C. The soils have a slow infiltration rate when thoroughly wetted. They chiefly have a layer that impedes downward movement of water or have moderately fine to fine texture. They have a slow rate of water transmission.

D. (High runoff potential). The soils have a very slow infiltration rate when thoroughly wetted. They chiefly consist of clay soils that have a high swelling potential, soils that have a permanent high water table, soils that have a claypan or clay layer at or near the surface, and shallow soils over nearly impervious material. They have a very slow rate of water transmission.

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Dual hydrologic groups, A/D, B/D, and C/D, are given for certain wet soils that can be adequately drained. The first letter applies to the drained condition, the second to the undrained. Only soils that are rated D in their natural condition are assigned to dual classes Soils may be assigned to dual classes. Soils may be assigned to dual groups if drainage is feasible and practical.

Definition.—“Drainage class” identifies the natural drainage condition of the soil. It refers to the frequency and duration of wet periods

DRAINAGE CLASSDRAINAGE CLASS

wet periods.

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Excessively Drained >6’ Somewhat Excessively Drained >6’ Well Drained 3.5 to 6’ Moderately Well Drained 2-3.5’ Somewhat Poorly Drained 1-2’ Poorly Drained 0-1’ Very Poorly Drained +1’

7 Drainage Classes used in MO7 Drainage Classes used in MO

Very Poorly Drained +1

Saturated hydraulic conductivity or KsatPertains to the

amount of water that would move downward through a

Natural Drainage ClassRefers to the frequency

and duration of wet periods similar to those under which the soil developed.

KsatKsat vs. DRAINAGEvs. DRAINAGE

gunit area of saturated in-place soil in unit time under unit hydraulic gradient.

Air space size Air space quantity Changes impact physical processes in the

soil. Such as adhesion, cohesion, adsorption, and surface tension.

Soil Air Space & Water MovementSoil Air Space & Water Movement

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Compaction breaks down the natural soil structure.

Compaction changes the air space size and quantity.

Soil CompactionSoil Compaction

◦ Saturated flow (also called gravitational flow) occurs only under saturated conditions when the force of gravity is greater than forces holding water in the soil.

Capillary flow occurs in unsaturated soil (also called unsaturated flow). Unbroken films of

t d th h t d ill water spread through connected capillary pores.

Flow terminologyFlow terminology

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SUMMARY:SUMMARY: PRIMARY CONTROL OF WATER MOVEMENT IN SOIL: --Soil

Texture – particle size distribution; Soil Structure; Organic Matter Content, Landform – hill slope profile.

Saturated flow (also called gravitational flow) occurs only under saturated conditions when the force of gravity is greater than forces holding water in the soil.o ces o d g ate t e so

The more accurate and site specific, the more effective the drainage system.

Soils are inherently complicated; therefore so is soil water movement.

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1/7/2013

Wetland Determinations

• Food Security Act – USDA Program Participants.

• Clean Water Act – Applies to all.

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1/7/2013

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1/7/2013

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1/7/2013

RedoxiRedoximorphmorphicicFeaturesFeatures

The shapes and forms of bodies resulting from the reduction and

oxidation of iron

Gray Redox Depletion

Describe Soil Colors

Soil Matrix Color

Reddish Redox Concentration

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1/7/2013

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1/7/2013

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1/7/2013

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1/7/2013

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14–161(210-VI-NEH, April 2001)

Figure 1 Symbols for auger-hole method of measuring hydraulic conductivity

(1) Auger-hole method

The auger-hole method is the simplest and most accu-rate way to determine soil permeability (fig. 1). Themeasurements obtained using this method are a com-bination of vertical and lateral conductivity, however,under most conditions, the measurements representthe lateral value. The most limiting obstacle for usingthis method is the need for a water table within thatpart of the soil profile to be evaluated. This limitationrequires more intensive planning. Tests must be madewhen a water table is available during the wet season.Obtaining accurate readings using this method re-quires a thorough knowledge of the procedure.

The principle of the auger-hole method is simple. Ahole is bored to a certain distance below the watertable. This should be to a depth about 1 foot below theaverage depth of drains. The depth of water in the holeshould be about 5 to 10 times the diameter of the hole.The water level is lowered by pumping or bailing, andthe rate at which the ground water flows back into thehole is measured. The hydraulic conductivity can thenbe computed by a formula that relates the geometry ofthe hole to the rate at which the water flows into it.

(i) Formulas for determination of hydraulic

conductivity by auger-hole method—Determina-tion of the hydraulic conductivity by the auger-holemethod is affected by the location of the barrier orimpermeable layer.

A barrier or impermeable layer is defined as a lesspermeable stratum, continuous over a major portion ofthe area and of such thickness as to provide a positivedeterrent to the downward movement of groundwater. The hydraulic conductivity of the barrier mustbe less than 10 percent of that of the overlying mate-rial if it is to be considered as a barrier. For the casewhere the impermeable layer coincides with thebottom of the hole, a formula for determining thehydraulic conductivity (K) has been developed by VanBavel and Kirkham (1948).

Kr

SHyt

=

2220 ∆∆

[1]

Appendix 14D Auger-hole Procedure for HydraulicConductivity

Ground water Level

H

G

yoyty

y

d

Impermeable layer

2r

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Chapter 14

(210-VI-NEH, April 2001)

Water Management (Drainage) Part 650Engineering Field Handbook

14–162

where:S = a function dependent on the geometry of the

hole, the static depth of water, and the averagedepth of water during the test

K = hydraulic conductivity (in/hr)H = depth of hole below the ground water table (in)r = radius of auger hole (in)y = distance between ground water level and the

average level of water in the hole (in) for thetime interval t (s)

∆y = rise of water (in) in auger hole during ∆tt = time interval (s)G = depth of the impermeable layer below the

bottom of the hole (in). Impermeable layer isdefined as a layer that has the permeability ofno more than a tenth of the permeability of thelayers above.

d = average depth of water in auger hole during test(in)

A sample form for use in recording field observationsand making the necessary computations is illustratedin figure 2. This includes a chart for determining thegeometric function S for use in the formula for calcula-tion of the hydraulic conductivity.

The more usual situation is where the bottom of theauger hole is some distance above the barrier. Formu-las for computing the hydraulic conductivity in homo-geneous soils by the auger-hole method have beendeveloped for both cases (Ernst, 1950). These formu-las (2 and 3) are converted to English units of mea-surement.

For the case where the impermeable layer is at thebottom of the auger-hole, G = 0:

Kr

H ryH

y

yt

=+( ) −

15 000

10 2

2, ∆∆ [2]

For the case where the impermeable layer is at a depth≥ 0.5H below the bottom of the auger hole:

Kr

H ryH

y

yt

=+( ) −

16 667

20 2

2, ∆∆ [3]

The following conditions should be met to obtainacceptable accuracy from use of the auger-holemethod:

2r > 2 1/2 and < 5 1/2 inchesH > 10 and < 80 inchesy > 0.2 HG > Hy < 1/4 yo

Charts have been prepared for solution of equation 3for auger-holes of r = 1 1/2 and 2 inches. For the casewhere the impermeable layer is at the bottom of theauger hole, the hydraulic conductivity may be deter-mined from these charts by multiplying the valueobtained by a conversion factor f as indicated onfigure 3.

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Part 650Engineering Field Handbook

14–163

Chapter 14 Water Management (Drainage)


Figure 2a Auger-hole method of measuring hydraulic conductivity—sheet 1 of 2

Distance to water surfacefrom reference point

Beforepumping

Afterpumping

Duringpumping

B A R A-R R-B

Residualdrawdown

Inches Inches Inches InchesSeconds Seconds Inches

XX

81.5

XX

79.0

77.5

76.0

74.0

72.0

XX

0.00

9.5

XX

38.5

36.0

34.5

33.0

31.0

29.0

XX

0.0

30

60

90

120

150

XX

XX

150

43

XX

Start

Elapsed

Time

10:03t y

Soil Conservation District________________________________ Field Office_________________________

Cooperator_____________________________________________ Location__________________________

SCD Agreement No.__________________Field No.____________ Farm No.__________________________

Technician_____________________________________________ Date______________________________

Boring No.__________ Salinity (EC) Soil _________ Water___________ Estimated K__________________

Field Measurement of Hydraulic ConductivityAuger-Hole Method

For use only where bottom of hole coincides with barrier.Dry River

Joe Doe - Farm No. 2

264 4 B-817

1/2 Mi. E. Big Rock Jct.

Tom Jones 1 June 64

4 — 5.6 1.0 in/hr

0 50 100 150 200Time in seconds

20

30

40

50

Res

idua

l dra

wdo

wn

(R-B

) in

inch

es

Ref. pointsurfaceGround

Water table

Residualdrawdown

y

d

RA

H

D

B

Auger hole profile

Salt Flat

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Chapter 14



14–164

Figure 2a Auger-hole method of measuring hydraulic conductivity—sheet 2 of 2

Values of

0.0 0.2 0.4 0.6 1.0

10

8

6

4

2

0

Val

ues

of S

Ref. pointSurfaceGround

Water table

Residualdrawdown

y

d

R

A

H

D

B

Auger hole profile

Hole dia.______Hole depth___________________

D=______ r=______ H=______ d=______ y=______ t=______secondsr/H=______/ ______=______d/H=______/______=______ S=______ K=2220 x

K=________

84" Ground to Ref.=11"4"

93"25016.29.51502 50 0.04

50 0.3216.24.7

1.2 in/hr

r/H=0.02

0.10

r/H=0.30

0.06

0.04

0.8dH

0.16

r

________(4.7) (50)

2 ________1509.5

x

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14–165



Distance to water surfacefrom reference point

Beforepumping

Afterpumping

Duringpumping

B A R A-R R-B

Residualdrawdown

Inches Inches Inches InchesSeconds Seconds Inches

Start

Elapsed

Time

10:03t y

Soil Conservation District________________________________ Field Office_________________________

Cooperator_____________________________________________ Location__________________________

SCD Agreement No.__________________Field No.____________ Farm No.__________________________

Technician_____________________________________________ Date______________________________

Boring No.__________ Salinity (EC) Soil _________ Water___________ Estimated K__________________

Field Measurement of Hydraulic ConductivityAuger-Hole Method

For use only where bottom of hole coincides with barrier.

0 50 100 150 200Time in seconds

20

30

40

50

Res

idua

l dra

wdo

wn

(R-B

) in

inch

es

Ref. pointsurfaceGround

Water table

Residualdrawdown

y

d

RA

H

D

B

Auger hole profile

Figure 2b Auger-hole method of measuring hydraulic conductivity—sheet 1 of 2 (blank)

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Chapter 14



14–166

Figure 2b Auger-hole method of measuring hydraulic conductivity—sheet 2 of 2 (blank)

Values of

0.0 0.2 0.4 0.6 1.0

10

8

6

4

2

0

Val

ues

of S

Ref. pointSurfaceGround

Water table

Residualdrawdown

y

d

R

A

H

D

B

Auger hole profile

Hole dia.______Hole depth___________________

D=______ r=______ H=______ d=______ y=______ t=______secondsr/H=______/ ______=______d/H=______/______=______ S=______ K=2220 x

K=________

84" Ground to Ref.=11"4"

93"25016.29.51502 50 0.04

50 0.3216.24.7

1.2 in/hr

r/H=0.02

0.10

r/H=0.30

0.06

0.04

0.8dH

0.16

r

________(4.7) (50)

2 ________1509.5

x

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14–167



Figure 3 Hydraulic conductivity—auger-hole method using the Ernst Formula

100

90

80

70

C

H

60

50

40

15 20 30 40 50 60 70 80 90 100

90

80

70

60

50

40

H

8

16

24

36

48

60

72

f

1.54

1.40

1.31

1.22

1.16

1.13

1.10

SOIL CONSERVATION SERVICE

ENGINEERING DIVISION-DRAINAGE SECTION

U.S. DEPARTMENT OF AGRICULTURESTANDARD DWG. NO.

ES-734SHEET OF

DATE

1 2

3-23-71

REFERENCE From formula L.F. Ernst

Groningen, The Netherlands

y=8

10

12

14

16

18

2022

24

27

30

33

36

42

485460

72

30

25

20

15

10

8

6

K Cyt

r= =∆∆

, 2 in

For G = 0 (bottom hole at imp. layer)

K = Kf′

H y

C

= ==

40 12

41∆∆yt

= =0 3210

0 032.

.Example

K = × =41 0 032 1 31. . in/hr

Kr

H ryH

y

yt

=+( ) −

16 667

20 2

2, ∆∆

Conditions:

and in

and in

in / hr

H, r, y, inches

seconds

2 212

512

10 80

0 2

34

r

H

y H

G H

y y

K

y

t

t o

> <

> <>>

≤

==

=

.

∆∆

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Chapter 14



14–168

Figure 3 Hydraulic conductivity—auger-hole method by Ernst Formula—continued

40

100

90

80C

H

70

60

15 20 30 40 50 60 70 80 90 100

90

80

70

60

50

H

8

16

24

36

48

60

72

f

1.54

1.40

1.31

1.22

1.16

1.13

1.10

SOIL CONSERVATION SERVICE

ENGINEERING DIVISION-DRAINAGE SECTION

U.S. DEPARTMENT OF AGRICULTURESTANDARD DWG. NO.

ES-734SHEET OF

DATE

2 2

3-23-71

REFERENCE From formula L.F. Ernst

Groningen, The Netherlands

30

25

20

15

10

8

6

10

y=8

12

14

16

18

20

24

28

32

3640

48

Conditions:

and in

and in

in / hr

H, r, y, inches

seconds

2 212

512

10 80

0 2

34

r

H

y H

G H

y y

K

y

t

t o

> <

> <>>

≤

==

=

.

∆∆

For G = 0 (bottom hole at imp. layer)

K = Kf′

K Cyt

r

=

=

∆∆

112

inches

H

G

C

f

===

=

24

0

44

1 25.

y

yt

K

K

=

= =

= ( )( ) =

′ = ( )( ) =

10

1 420

0 07

44 0 07 3 1

3 1 1 25 3 9

∆∆

..

. .

. . . in/hr

Example

Kr

H ryH

y

yt

=+( ) −

16 667

20 2

2, ∆∆

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14–169



Figure 4 Equipment for auger-hole method of measuring hydraulic conductivity

(ii) Equipment for auger-hole method—Thefollowing equipment is required to test hydraulicconductivity:

• suitable auger• pump or bail bucket to remove water from the

hole• watch with a second hand• device for measuring the depth of water in the

hole as it rises during recharge• well screen may be necessary for use in unstable

soils

Many operators prefer a well made, light weight boator stirrup pump that is easily disassembled for clean-ing. A small, double diaphragm barrel pump has givengood service. It can be mounted on a wooden framefor ease of handling and use.

For the depth measuring device, a light weight bam-boo fishing rod marked in feet tenths and hundredthsand that has a cork float works well. Other types offloats include a juice can with a standard soldered toone end to hold a light weight measuring rod.

A field kit for making the auger hole measurement ofhydraulic conductivity is illustrated in figure 4. Inaddition to the items indicated in this figure, a watchand a soil auger are needed.

A perforated liner for the auger-hole is used in makingthe auger-hole measurement in fluid sands. This linerkeeps the hole open and maintains the correct size.Several types of liners are used. Adequate slot open-ings or other perforations must be provided to allowfree flow into the pipe.

��

��5 3/4"

2'-2 3/4"

1'-3 1/2"

7 1/2"

Double diaphragmbarrel pump

Top view

Mounting for pump

1 1/2"

Side view �� 3/4"

��

Measuringpoint

Pump

Exhausthose

Standard

Staticwaterlevel

Finish test

Start test

Suction hose

Tape and 2-inch float

Note: In addition to the pump,the equipment in the carrying caseincludes suction hose, tape and float,stake, and standard.

Field set-up

Carrying case–auger hole kit

9 3/16"

2'-5 7/32"

1' -1/8"

(Assembled)

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Chapter 14



14–170

The openings in the screen should not restrict flowappreciably. The head loss through the screen shouldbe negligible, and the velocity of flow through theopenings should be small (0.3 foot per second or less)to prevent movement of fines into the hole. Thesecriteria generally are met if the area of openings is 5percent or more of the total screen area.

The Bureau of Reclamation uses 4-inch downspoutingwith 60 1/8- by 1-inch slots per foot of length. Thisworks well in a variety of soils. A screen from theNetherlands is made from a punched brass sheet 2millimeters thick with holes averaging about 0.5 milli-meter in diameter. It is rolled into a tube 8 centimetersin diameter by 1 meter long. This screen works wellbecause the sheet is rolled so that the direction inwhich the holes are punched is outward and the holesare variable in size. It has been used in many trouble-some soils, and no clogging or failure to keep fines outof the hole has been reported.

Good judgment is needed in determining how far todrawdown the water level in the auger hole for thetest. A minimum drawdown is necessary to physicallysatisfy theoretical criteria (refer to conditions given infig. 3). Generally, a larger drawdown is made forslowly permeable soils than that for more permeablesoils. A small drawdown for holes in sloughing soilsmay reduce the amount of sloughing. To preventpicking up sand in the pump, pumping should stopwhen the water level is within a few inches of thebottom of the hole.

Measurement of the rate of recovery of water in theauger hole should be completed before a fourth of thetotal amount of drawdown is recovered. Four or fivereadings should be taken at uniform short time inter-vals, and a plot of the readings made to determine auniform rate of recovery to use in the formula. Plottingof time in seconds against the residual drawdown ininches indicates those readings at the beginning andend of the test that should be discarded and the propervalues of t and y to use.

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Drainage Design Reference

Area

1 acre = 43,560 square feet

Saturated Hydraulic Conductivity

1 micrometer per second = 1 μm/sec

1 μm/sec = 0.2834 feet per day

1 μm/sec = 0.1417 inch per hour

1 inch per hour = 7.0572 μm/sec

1 inch per hour = 2 feet per day

Pipe Flow

Q = V x A and V = Q ÷ A

Where: Q = Flow discharge rate, cubic feet per second

V = Flow velocity, feet per second

A = Cross Sectional Area, square feet

Required Drainage Capacity

Q = 0.042 x DC x DA

Where Q = Flow discharge rate, cubic feet per second

DC = Drainage Coefficient, inch/day

DA = Drained Area, acres

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705.00 100.00 705.00 100.00

VERY HIGH141.14

VERY RAPID

20.00

100.00 14.17

14.11

MODERATELY RAPID 2.00

VERY LOW IMPERMEABLE0.00 0.00 0.00 0.00

μm/sec in/hr μm/sec in/hr

in/hr x 7.0572 = μm/sec

μm/sec x 0.2834 = ft/day in/hr x 2 = ft/day

4.23

6.00

1.00

MODERATEMODERATELY

HIGH

MODERATELY LOW

0.001417

0.42

SATURATED HYDRAULIC CONDUCTIVITY - PERMEABILITY

Permeability ClassKsat Class

10.00

RAPID

42.34

MODERATELY SLOW

SLOW

0.60

0.20

0.06

0.0015

VERY SLOW

μm/sec x 0.1417 = in/hr

0.01

LOW

HIGH

1.41

1.417

0.1417

0.014170.10

0.01

MLICA 4-42

Soil Water

Soil Water

Saturatio

nWilting Po

int

Field Capacity

Drainable

Water

Available

Water

Air

Soil

Water

MLICA 4-43

DRAINAB

LE W

ATER

3‐11%

PLAN

T AV

AILABLE WATER

(Weak Ca

pillary Forces)

13‐21%

UNAV

ALAB

LE W

ATER

(Stron

g Ad

sorptive Forces) 15‐24%

SOIL SOLIDS

45‐65%

← Field Capacity

← Com

pletely Dry

← W

ilting Po

int

← Saturation

Pore Volume(Air and Water)

Solids Volume(Mineral and Organic Mater)

Soil Water

Relatio

nships

(Typical fo

r Clay, Clay

Loam

and

Silty Clay)

Soil Water

Relatio

nships

(Typical fo

r Clay, Clay

Loam

and

Silty Clay)

MLICA 4-44

Typical Soil W

ater Relationships

Typical Soil W

ater Relationships

Soil Texture

WiltingPo

int

(% by vol.)

Available

Water

(% by vol.)

Drainab

leWater

(% by vol.)

clays, clay loam

s,

siltyclays

15‐24

15‐26

3‐11

well structuredloam

s8‐17

12‐22

10‐15

sand

y3‐10

7‐20

18‐35

Source: University

of M

inne

sota BU‐07644

‐S, Soil W

ater Con

cepts, Gary Sand

s

MLICA 4-45

DRAINAB

LE W

ATER

5%

PLAN

T AV

AILABLE WATER

(Weak Ca

pillary Forces)

20%

SOIL SOLIDS

55%

← Field Capacity

← Com

pletely Dry

← W

ilting Po

int

←Saturatio

nPore Volume

(Air and Water)Solids Volume

(Mineral and Organic Mater)

UNAV

ALAB

LE W

ATER

(Stron

g Ad

sorptive Forces) 20%

Soil Water

Relatio

nships

(Example Silty

Clay)

Soil Water

Relatio

nships

(Example Silty

Clay)

MLICA 4-46

How

much water do I n

eed to re

move?

How

much water do I n

eed to re

move?

Given

a so

il (silty clay) w

ith a drainable porosity

of 5

%

with

the goal of d

raining the top 12

inch layer in 48

hou

rs.

Volume of drainab

le water

= 5%

x 12 inch dep

th

= 0.6 inches

Rate of rem

oval

= 0.6 inch ÷2 day

= 0.3 inch/day

MLICA 4-47

How

much water do I n

eed to re

move?

How

much water do I n

eed to re

move?

Given

a so

il (lo

am) w

ith a drainable porosity

of 1

2%

with

the goal of d

raining the top 12

inch layer in 48

hou

rs.

Volume of drainab

le water

= 12

% x 12 inch dep

th

= 1.4 inches

Rate of rem

oval

= 1.4 inch ÷2 day

= 0.7 inch/day

MLICA 4-48

soil forming factors - missouri land improvement...

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