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Geohydrology and numerical model analysis of ground-water flow in the Pullman-Moscow area, Washington and Idaho. U.S. Geological Survey Water-resources investigations report 89-4103 Item Info

The Pullman-Moscow area of southeastern Wash ton and northern Idaho depends on ground water as the principal source of water, but increasing pumpage rates and declining ground-water levels indicate a need for ground-water management. Using data from a study done by the U.S. Geological Survey in the 1970's and up-to-date data collected for this study, a three-dimensional numerical computer model of the ground-water-flow system was constructed to provide an understanding of the geohydrology of the study area. The ground-water-flow model incorporates three layers -- an overlying surficial loess layer, a Wanapum Basalt layer, and a Grande Ronde Basalt layer. A ground-water-system recharge rate was estimated using a methodology developed by the U.S. Geological Survey. Ground-water discharge was modeled as ground-water pumping, flow to rivers and streams, and flow out of seepage faces, where a layer is incised by a river valley. Three cross-sectional flow models, distributed across the domain of the three-dimensional model along estimated flow lines in the Grande Ronde Basalt, were used to obtain hydraulic coefficient input for the three-dimensional model. The three-dimensional model was calibrated using the time-averaged method for the period 1974-85, and was evaluated by simulating historical pumpage rate changes (1890-1985) and comparing simulated with observed water-level changes. Model results suggest that ground-water levels would stop declining if ground-water pumpage were to stabilize at a constant level. However, ground-water levels will continue to decline in the foreseeable future as long as ground-water pumpage continues to increase. Further study of the recharge, movement, and discharge of ground water in the area is needed to increase the accuracy of any ground-water-flow model to predict the response of the flow system to future pumping stresses.

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Title:
Geohydrology and numerical model analysis of ground-water flow in the Pullman-Moscow area, Washington and Idaho. U.S. Geological Survey Water-resources investigations report 89-4103
Authors:
Lum, W. E. II; Smoot, J. L.; Ralston, D. R.
Date Created (ISO Standard):
1990
Description:
The Pullman-Moscow area of southeastern Wash ton and northern Idaho depends on ground water as the principal source of water, but increasing pumpage rates and declining ground-water levels indicate a need for ground-water management. Using data from a study done by the U.S. Geological Survey in the 1970's and up-to-date data collected for this study, a three-dimensional numerical computer model of the ground-water-flow system was constructed to provide an understanding of the geohydrology of the study area. The ground-water-flow model incorporates three layers -- an overlying surficial loess layer, a Wanapum Basalt layer, and a Grande Ronde Basalt layer. A ground-water-system recharge rate was estimated using a methodology developed by the U.S. Geological Survey. Ground-water discharge was modeled as ground-water pumping, flow to rivers and streams, and flow out of seepage faces, where a layer is incised by a river valley. Three cross-sectional flow models, distributed across the domain of the three-dimensional model along estimated flow lines in the Grande Ronde Basalt, were used to obtain hydraulic coefficient input for the three-dimensional model. The three-dimensional model was calibrated using the time-averaged method for the period 1974-85, and was evaluated by simulating historical pumpage rate changes (1890-1985) and comparing simulated with observed water-level changes. Model results suggest that ground-water levels would stop declining if ground-water pumpage were to stabilize at a constant level. However, ground-water levels will continue to decline in the foreseeable future as long as ground-water pumpage continues to increase. Further study of the recharge, movement, and discharge of ground water in the area is needed to increase the accuracy of any ground-water-flow model to predict the response of the flow system to future pumping stresses.
Subjects:
Groundwater Groundwater development Confined aquifers Unconfined aquifers Water supply Computer models
Location:
Pullman; Moscow; Northern Idaho
Latitude:
46.74
Longitude:
-117.17
Collection:
Palouse Basin
IWRRI number:
199004
Rights:
Rights to the digital resource are held by the University of Idaho. http://www.uidaho.edu/
Publisher:
Idaho Water Resources Research Institute; University of Idaho
Contributing Institution:
University of Idaho
Type:
Text
Format:
application/pdf
Cataloger:
KIT
Date Digitized:
2017-09-12

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Preferred Citation:
"Geohydrology and numerical model analysis of ground-water flow in the Pullman-Moscow area, Washington and Idaho. U.S. Geological Survey Water-resources investigations report 89-4103", Idaho Waters Digital Library, University of Idaho Library Digital Collections, https://www.lib.uidaho.edu/digital/iwdl/items/iwdl-199004.html
Rights
Rights:
Rights to the digital resource are held by the University of Idaho. http://www.uidaho.edu/
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