hydrologic conditions in the palouse aquifer dale r. ralston professor emeritus of hydrogeology...

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!!