Hydrogeological Modeling of the Pullman-Moscow Basin Basalt

Aquifer System, WA and ID

Joan Wu, Farida Leek, Kent Keller

Washington State University

John Bush

University of Idaho

2

OUTLINE

Introduction Hydrogeologic Setting Methodology

GIS database development Ground-water flow modeling

Results and Discussions Summary Position Announcement

3

INTRODUCTION

The aquifer system in the CRBG is the sole water supply source for the Palouse Basin

The continuous water-level decline and the projected future development have led to serious public concerns

PBAC: a multi-stakeholder, multi-agency (city, county, university) organization promoting conservation and sound ground-water management

The 2003 MOA with PBAC: GIS database

4

INTRODUCTION (cont’d)

Past Studies on Hydrogeological Characterization Crosby and Cavin (1960) Foxworthy and Washburn (1963); Jones and Ross

(1972) Bush and colleagues (1998, 2000, 2001, 2003)

Past Studies on Groundwater Modeling Barker (1979), overly conservative Lum et al. (1990), overly optimistic Both models proved inadequate by year 2000

5

INTRODUCTION (cont’d)

Goal To develop a foundation for improved and informed

Palouse Basin groundwater resources assessment and management

Objectives To develop a hydrogeology GIS database for the

Palouse Basin to improve data accessibility and data processing and analysis efficiency

To develop a groundwater flow model for the basaltic aquifer system of the Pullman-Moscow area based on new spatial and temporal data

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HYDROGEOLOGIC SETTING

Palouse loess Saddle Mts. Wanapum basalt Grande Ronde basalt Imnaha basalt Pre-basalt

CRBG

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HYDROGEOLOGIC SETTING (cont’d)

Palouse loess: rural domestic use Wanapum basalt: major aquifer for Moscow

till 1960’s Grande Ronde basalt: source for more than

90% of water supply, with a recent construction of WSU #8

Occurred during late Miocene and early Pliocene (17–6 mya BP)

Engulfing ~ 1.6×105 km2 of the Pacific Northwest between Cascade Range and Rocky Mt., covering parts of ID, WA, and OR

Over 300 high-volume individual lava flows identified, along with countless smaller flows, with vents up to 150 km long

Eventually accumulating to more than 1,800 m thick

Tectonic origin (Hooper, 1997) Yellowstone hot spot Thinning of continental

lithosphere due to spreading behind Cascade arc

Proximity of fissure vents to tectonic boundary between accreted terranes and lithospheres of old N. Am. Plate

Source: USGS, http://vulcan.wr.usgs.gov/

Source: ND Space Grant Consortium, http://volcano.und.edu/

12

METHODOLOGY:I. GIS DATABASE DEVELOPMENT

Data Collection Well log Groundwater level Pumpage Precipitation Geochemistry

Data Compilation Digitizing into ArcGIS Processing existing and new coverages:

• Topography• Township and range to UTM conversion of well coordinates• Stream network• Land use• Soil• Watershed boundary

Digitizing & Processing Well Data

Well 15/46-31J1 Well 39N/5W-7ad2

A

R 45E R 46E R 6 W R 5 W T 16N T 4 0 N

T 15N T 3 9 N

T 14N T 3 8 N

WA

SH

ING

TO

N

IDA

HO

R 46E

6 5 4

7 8 9

T 15N 18 17 16

19 20 21

30 29 28

31 32 33

R 5 W

6 5 4 3 2 1

7 8 9 10 11 12

18 27 16 15 14 13

19 20 21 22 23 24

30 29 28 27 26 25

31 32 33 34 35 36

D C B A

E F G H

M L K J

N P Q R

b a

c d a

Digitizing & Processing Well Data cont’d

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Data Analysis Plot long-term hydrographs

• Separate vs composite• Their relations with precipitation and pumpage

Build structural contour maps• To depict the shape of stratigraphic horizons

Construct aquifer contour maps• Wanapum• Grande Ronde

Develop hydrogeological cross-sections• Across most of the basin• In various directions

METHODOLOGY:I. GIS DATABASE DEVELOPMENT

RESULTS AND DISSCUSSION:I. GEOSPATIAL DATA ANALYSIS

Composite Hydrograph for Palouse Basin Aquifer

Year

1923 1931 1939 1947 1955 1963 1971 1979 1987 1995 2003

Wat

er L

evel

Ele

vatio

n, a

.m.s

.l., f

t

2200

2250

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2500

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2700

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Moscow # 1 Moscow # 2 Private well (Freight)UI # 2Moscow # 3 Moscow-Arden UI-Irrigation UI # 1 Moscow # 7Cemet. well

Private well (Carson)

Jones EvelandUSGS

Wanapum

Palouse LoessPullman # 1 Pullman # 2 Pullman # 3 Moscow # 6 Moscow # 9 UI # 4 Pullman # 4 Pullman # 6 WSU # 3 WSU # 4 WSU # 5 WSU # 6 WSU # 7 UI # 3 Pullman # 5 WTESTPullman # 7 Moscow # 8

Grande Ronde

Composite Hydrograph of Wells in the Palouse Basin

Long-term Hydrograph for Pullman and WSU Grande Ronde Wells

Year

1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004

Wat

er L

evel

, Ele

vati

on, a

.m.s

.l., f

t

2230

2235

2240

2245

2250

2255

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2265

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2275

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2285

2290

2295

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2305

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2240

2245

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2255

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Pullman 3 Pullman 4 Pullman 6 Pullman 5 Pullman 1 Pullman 2 Pullman 7 DOEWSU 3 WSU 4 WSU 5 WSU 6 WSU 7 WTEST

Long-term Hydrograph for Moscow and UI Grande Ronde Wells

Year

1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004

Wat

er L

evel

Ele

vati

on, a

.m.s

.l., f

t

2220

2225

2230

2235

2240

2245

2250

2255

2260

2265

2270

2275

2280

2285

2290

2295

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Moscow 6 Moscow 8 Moscow 9 UI 3 UI 4

(a)

Year

1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

An

nu

al P

um

pag

e, M

GY

0

500

1000

1500

2000

2500

3000

3500

An

nu

al precip

itation

, mm

Pullman pumpageMoscow pumpageTotal pumpagePullman precipitationMoscow precipitation

(a)

0

500

1000

Long-term Groundwater Pumpage from Two Aquifers

28

Long-term Hydrographs

Each aquifer has a distinct pattern of water-level fluctuations in relation to pumping, climate, recharge

Wanapum saw its groundwater level recovery since 1960’s when pumping shifted to the Grande Ronde

Relatively more consistent pattern of fluctuation in Grande Ronde wells in Pullman than in Moscow

0.3–0.6 m/yr groundwater level decline observed at both pumping centers

Contour Map of Top Altitude of Wanapum Formation

Contour Map of Top Altitude of Grande Ronde Formation

32

Structural Contour Maps

Wanapum Wanapum basalt is to the NW controlled by NW

trending folds, and dips and thickens E and W away from Pullman

Grande Ronde The top of GR drops in elevation E towards Moscow

and W and NW away from Pullman Substantial lateral changes in the occurrence and

nature of sediments exist between Pullman and Moscow

Potentiometric surface contour map of the Wanapum aquifer (1960s)

Potentiometric surface contour map of the G. Ronde aquifer (1990s)

35

Potentiometric Surface Contour Maps

Wanapum Hydraulic connection between Pullman and Moscow is

weak General groundwater movement is to W and NW

Grande Ronde Piezometric surface shows two cones of depression as

a result of heavy pumping

The open shape of cones of depression to the W and NW is possibly controlled by structural features

METHODOLOGY:II. DEVELOPING A NEW MODEL

41

Water Release from a Confined Aquifer: Water Expansion + Aquifer Compression

Source: http://www.bae.uky.edu/sworkman/AEN438G/theiseq/theiseq.html

42

Unsteady-State Flow in “Ideal” Aquifer: Theis (1935) Equation

Source: http://www.olemiss.edu/sciencenet/saltnet/theisbio.html

“The flow of ground water has many analogies to the flow of heat byconduction. We have exact analogies … for thermal gradient, thermalconductivity, and specific heat…solution of some of our problemsis probably already worked out in the theory of heat conduction…”

43

Unsteady-State Flow in “Ideal” Aquifer: The Solution

“Actually derived by a mathematician friend of Theis, C.I. Lubin.Reportedly, Lubin declined co-authorship of the paper becausehe regarded his contribution as mathematically trivial.” [Fetter, 1994]

44

Groundwater Flow Model Development

Industry standard MODFLOW MODular 3-d finite-difference

groundwater FLOW model Free source codes from the USGS

and GUI versions available

PEST (nonlinear parameter estimator) can be used with MODFLOW for optimal parameterization

Source: http://water.usgs.gov/nrp/gwsoftware/modflow2000/modflow2000.html

45

Comparison of Model Domain and Structure

Barker (1979)Western BC at Union Flat Cr.;

One lumped basalt aquifer; “single-layer-cake”

Lum et al. (1990)

Western BC at Snake R.;

Palouse Loess + two separate basalt aquifers, layers horizontal

New ModelWestern BC as in Barker (1979);

Three model layers with actual top/bottom altitudes

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Barker (1979) Dirichlet (head) at Union Flat Cr. for lumped aquifer

Lum et al. (1990)Cauchy (weighted head and flux) at Snake R. for all three aquifers

New Model Same as in Barker (1979) but for three distinct aquifers

Comparison of Western Boundary Condition

47

Comparison of Hydraulic Parameterization

Barker (1979)Uniform hydraulic properties within zones:

Kh = Kv = 0.03–7.9 m/d, S = 0.005

Lum et al. (1990)

Uniform hydraulic properties within zones of each aquifer:

Loess: Kh = 1.5 m/d, Kv = 0.02 m/d

Wanapum: Kh = 0.1–0.2 m/d, Kv = 2.4–3.6×10−4 m/d

Grande Ronde: Kh = 0.1–3.7 m/d, Kv = 3.1–76×10−5 m/d

S = 0.001

New ModelApply inverse modeling to a wealth of historical head data for greatly improved parameterization

Comparison of Hydraulic Parameterization

48

Barker (1979) 17 mm yr−1 uniform across model domain

Lum et al. (1990) 71 mm yr−1 uniform across model domain

New Model

Spatially varying following O’Green (2005):

3 mm yr−1 in 33% (near Moscow Mt.),

10 mm yr−1 in 37% (Pullman area),

actual infiltration in 10% (valleys) of the basin area

Comparison of Recharge Distribution

49

Aerial RechargeRecharge needs: 14 mm

Winter wheat consumes up to 90% annual precipitation of 550 mm

Winter runoff loss unavoidable from conventionally farmed fields

Low permeability across Bovill sediment–Wanapum basalt contact in places

Transporting Surface Water from Snake R.Economic feasibility low but of potential

Artificial RechargeOf greatest potential when using streams incised into Wanapum

Ground-water modeling imperative in determining the effectiveness

Given: pumpage needs 2,400 MGY = 9.1×106 m3, basin area 660 km2

Management Alternatives

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SUMMARY AND CONCLUSIONS

GIS database has in the first time brought together the various scattered data pertinent to PBA hydrogeology and placed it in uniform and easily accessible form

Such database facilitates efficient data retrieval and analysis and allows continuous updating and refinement, forming a solid foundation for future trans-boundary hydrogeolocial investigation

A great deal has been learned from this newly available digital temporal and spatial data

Development of an improve basin-scale groundwater flow model is underway

THANK YOU !

52

Pullman─Moscow Cross-section

Pullman─Moscow Cross-sectionPullman side Less sedimentary interbedding Loess is in direct contact with the basalt Wanapum is unproductive

Moscow side More sedimentary interbeds Wanapum is highly productive Current hydraulic gradient and ground-water flow in

Grande Ronde between Pullman and Moscow is minimal, reflecting good hydraulic connection and lack of dike barrier as suggested by some scientists

53

Long-term Hydrographs Revisit

Relatively consistent pattern of fluctuation in Grande Ronde wells in Pullman Aquifer is shown to have been depressurized!

Greater fluctuation in Grande Ronde wells in Moscow due to Multi-layered sediment system Proximity to low-permeability boundaries created by

non-basaltic rocks Confined nature of aquifer All these factors tend to cause longer recovery period

for the wells to reach equilibrium

54

Pullman─Albion─Colfax Cross-section

Fracture patterns and degree of weathering dominantly control the productivity of wells

Grande Ronde dips eastward towards Colfax with a hydraulic head drop of 150 m

Intrusion of low-permeability pre-Tertiary rocks are considered to form barriers between Pullman and Colfax and cause the drastic change in hydraulic head

Certain previous pump test results may be questionable; substantial ground-water flow from Pullman to Colfax appears unlikely

55

Pullman–Union Flat Creek–Snake River

Significant difference (~460 m) exists in hydraulic heads of the Wanapum and Grande Ronde near the Snake R.; this sudden change in head may be related to the dip of the basalt flows to the NW away from the Snake R.

Cross-sections and potentiometric surface maps suggest a major flow direction of NW along the Snake R.; significant seepage along the canyon walls of the Snake R. from the Grande Ronde aquifer is unlikely

Geochemistry data from previous studies (Larson et al., 2000) also indicates a lack of Grande Ronde discharge to the Snake R.

56

SUMMARY AND CONCLUSIONS (cont’d)

Long-term trends of the hydrographs indicate weak vertical hydraulic connection between the two basalt aquifers, consistent with pervious isotope geochemistry studies

Each aquifer exhibits a distinct pattern of water-level fluctuation as affected by pumping, climate and recharge, with the top basalt aquifer seemingly receiving Holocene precipitation recharge and the bottom aquifer pre-Holocene recharge

57

SUMMARY AND CONCLUSIONS (cont’d)

Potentiometric surface contour maps of the basalt aquifers display a general pattern with the ground-water level dipping S–NW along the ancient basalt flow

Existing structural features (monoclines, anticlines and synclines) tended to create local areas with rapid changes in water levels in the approximate direction of their major axis

Previous modeling studies using Snake R. as a Cauchy boundary and forced high recharge may have been the key causes of the model failures

58

SUMMARY AND CONCLUSIONS

Geologic and hydrogeologic conditions at the two cities of Pullman, WA and Moscow, ID in the Palouse Basin are rather different; yet the hydraulic connection appears strong

The nature and position of stratigraphic units and their inherent spatial heterogeneity together with geologic structures have significant effects on the ground-water flow regime in a fractured complex basalt system, which should be carefully taken into account in future modeling efforts