hydrologic conditions in the palouse aquifer dale r. ralston professor emeritus of hydrogeology...
TRANSCRIPT
Hydrologic Conditions in the Palouse Aquifer
Dale R. RalstonProfessor Emeritus of HydrogeologyUniversity of Idaho
Outline of talk
IntroductionGround water management conceptsDescription of the Palouse aquiferWell development and water level declineResearch and management activitiesWater management questions
Ground Water Management Concepts
Long-Term Equilibrium - Recharge Equals
Discharge
STORAGE
INFLOW
OUTFLOW
INFLOW - OUTFLOW = 0
Ground Water Management Concepts
Water levels are stable prior to development or
when pumping amount is small
Time (years)
WaterLevel
Ground Water Management Concepts
Addition of Pumping Can Result in a New
Equilibrium
STORAGE
INFLOW
OUTFLOW
Water levels decline until inflow = outflow + withdrawal
Withdrawal
Ground Water Management Concepts
Development of well(s) with a constant pumping rate can result in water-level decline leading to a
new equilibrium
Time
Aquifer water level
Constant pumping rate
Ground Water Management Concepts
Development of wells with a increasing combined
pumping rate will result in continual water-level
decline
Time
Aquifer water level
Increasing pumping rate
Ground Water Management Concepts
General Geologic Setting Subsurface geology of the Palouse basin is dominated by basalt with layers of sediment, mostly along the east margin Basalt and sediment overlie older rocks that make up Moscow Mountain and Paradise Ridge
Outline of the Columbia River Basalt Group
Wanapum Formation: Priest Rapids Member
Wanapum Formation is the uppermost basalt unit in the Palouse basin
Priest Rapids member is present in most areas with the Rosa member present west of Pullman
This formation hosts the upper aquifer in the Palouse basin
Grande Ronde Formation
Grande Ronde basalt makes up the majority of the subsurface section in the Palouse basin and other locations in Eastern Washington and Northern Idaho
Formation is divided into four units based on paleo-magnetism
This formation hosts the lower aquifer in the Palouse basin and is the major water producer in Lewiston and in the Grangeville area
MP
Pa
Smoot Hill
KamiakButte
RingoButte
TomerButte
BaldButte
500
100020
00
1500
1500
WGS84 117º W
46
.9º
N4
6.7
º N
117.2º W
N0 1 2 3
miles
C
Moscow Mountain
Pre-Basalt Topography
Smoot Hill
KamiakButte
RingoButte
TomerButte
BaldButte
WGS84 117º W
46
.9º
N4
6.7
º N
117.2º W
N0 1 2 3
miles
? ?
Emplacem
ent
from
SW
Primary dip
Extent of R1 flows
Sedimentation
P M
Pa
C
Moscow Mountain
Geology After First Sequence of Grande Ronde Basalt
Geology After Second Sequence of Grande Ronde Basalt
Smoot Hill
KamiakButte
RingoButte
TomerButte
BaldButte
WGS84 117º W
46
.9º
N4
6.7
º N
117.2º W
N0 1 2 3
miles
? ?
Emplacem
ent
from
SW
Primary dip
Extent of N1 flows
Sedimentation
P M
Pa
C
Moscow Mountain
Smoot
Hill
KamiakButte
RingoButte
Tomer
Butte
Bald
Butte
P
Pa
WGS84 117º W
46
.9º
N4
6.7
º N
117.2º W
C
Moscow Mountain
SNAKE RIVER
Basalt Flow
Directio
n
M
N0 1 2 3
miles
Geology After Third Sequence of Grande Ronde Basalt
Smoot
Hill
KamiakButte
RingoButte
Tomer
Butte
Bald
Butte
P
Pa
WGS84 117º W
46
.9º
N4
6.7
º N
117.2º W
C
Moscow Mountain
SNAKE RIVER
Basalt Flow Direction
Flow Directio
n
?
M
Geology After Fourth Sequence of Grande Ronde Basalt
Area Hydrogeology - 1
Upper aquifer occurs in the Wanapum FormationLower aquifer occurs in the Grande Ronde FormationDepth to water in upper aquifer is about 60 feet while the depth to water in the lower aquifer is about 300 feet
Area Hydrogeology - 2
Recharge to upper aquifer occurs from infiltration of precipitation and stream lossRecharge to lower aquifer occurs primarily as downward leakage from upper aquiferRecharge to the upper aquifer is greater than to the lower aquifer although present estimates of recharge rates have large error band
Well Development and Water-Level Decline
Well development -- 1
In Moscow, the upper aquifer water levels declined until 1960’s when deep wells were drilled and withdrawal was shifted to lower aquifer – water levels now have recovered to 1940’s levelsCity of Moscow now withdraws about 30 percent from the upper aquifer
Hydrographs For Two Upper Aquifer Wells in Moscow
40
60
80
100
120
140
160
Jan-30 Jan-40 Jan-50 Jan-60 Jan-70 Jan-80 Jan-90 Jan-00 Jan-10
De
pth
to
wa
ter
in f
ee
t
City well at Jackson and A Streets
Private Well Near 6th and Asbury Streets
Well Development -- 2
Water level decline has been experienced in the lower aquifer in Moscow, Pullman and PalouseThere is considerable evidence that these three cities obtain water from the same aquifer system
Water Levels from Grande Ronde wells in Moscow and
Pullman
2,220
2,230
2,240
2,250
2,260
2,270
2,280
2,290
elev
atio
n (fe
et m
sl)
2,200
2,210
2,220
2,230
2,240
2,250
2,260
2,270
2,280
2,290
2,300
elev
atio
n (f
eet m
sl)
Moscow Wells Pullman Wells
M-6
M-8 M-9UI-3
WSU test
P-4
P-3
Research and Water Management Activities
Ground water model (1990)PBAC (Palouse Basin Aquifer Committee) formed and developed planPumping from the Grande Ronde aquifer has been stabilizedAdditional research on geology, water ages and water level patterns
Ground Water Model (1990)
Cooperative effort of USGS and UIRepresent upper and lower aquifersPrimary results Ground water levels will continue to
decline if pumping amounts continue to increase
Ground water levels will stop declining (within 10 to 15 years) if pumping is stabilized
Palouse Basin Aquifer Committee (PBAC) -- 1
Includes cities, Universities and counties from both statesGeneral goal is to ensure a long-term water supply for the basinThe goal of stabilizing pumping from the lower aquifer was accomplished in the 1990’s In 1999, PBAC’s revised goal was to stabilize ground water levels in lower aquifer by 2020 by conservation and possible recharge enhancementPBAC has supported and encouraged water conservation and aquifer research
GRAPH OF ANNUAL WATER PUMPED FROM THE GRANDE RONDE AQUIFER
0
500
1000
1500
2000
2500
3000
1975 1980 1985 1990 1995 2000 2005
Mill
ion
gallo
ns p
umpe
d pe
r yea
r PULLMAN
WSU
MOSCOW
UI
TOTAL
WSU Test Well Hydrograph
2240
2250
2260
2270
2280
2290
2300
1970 1980 1990 2000 2010
Elev
atio
n in
feet
Decline rate of about 1.4 ft/yr
Hydrographs for the DOE and WSU Test Wells
2246
2248
2250
2252
2254
2256
1/1999 1/2000 1/2001 1/2002 1/2003 1/2004 1/2005
Fee
t ab
ove
sea
leve
l
DOE
WSU Test
Linear (DOE)
Linear (WSU Test)
This trendline yields an annual decline of 0.7 ft/yr for the DOE well over the past 4 years.
This trendline for the WSU test well indicates a decline of 1.0 ft/yr over the past 4 years.
Palouse Basin Aquifer Committee (PBAC) -- 2
Ongoing research projects at both UI and WSU (geology, water levels, age dating of water) are leading to an improved understanding of the aquifer.Plans are underway to construct several test wells in areas where geologic and hydrologic data are limited.$100,000 federal appropriation, in process, will allow additional research.
Water Management Questions -- 1
Is the deep aquifer in the Moscow area part of a larger aquifer system that includes Pullman and Palouse and possibly Colfax and Garfield? Yes – the areas are hydraulically connected. Does this aquifer receive recharge? Yes – although we do not know if the recharge rate is greater than or less than the combined pumping rate of the four entities.
Water Management Questions – 2
Are we facing the loss of our water supply source in the near future? No – the quantity of water still in storage in the aquifer is large. However, we need to continue to take action to insure that we have a sufficient water supply into the future.
Water Management Questions -- 3
Is water conservation a long-term solution for the aquifer problem? Water conservation is important but may or may not be enough to insure that the area has a stable water source for decades into the future.
Water Management Questions -- 4
What can we do if stabilizing pumping does not stabilize water levels? PBAC is now investigating recharge enhancement alternatives and encouraging entities to turn to alternative sources of water.
Water Management Questions -- 5
Should water management activities be done separately by each of the states or as a combined effort? Since the same aquifer underlies both states, it makes sense to have combined management of the resource.
Thank you!!