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Geohydrology and digital simulation of the ground-water flow system in the Umatilla Plateau and Horse Heaven Hills area, Oregon and Washington

Water-Resources Investigations Report 87-4268

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Abstract

The Columbia Plateau is underlain by massive basalt flows, with a composite thickness of about 10,000 ft. Structural features within the study area include a series of anticline-syncline pairs. The main avenues of groundwater movement in the basalt are the interflow zone between basalt flows. Individual interflow zones may be rather extensive in the lateral direction and are largely isolated from overlying and underlying interflows by poorly permeable basalt flow centers. Four aquifers were defined for this study. The uppermost aquifer (layer 1) consists of unconsolidated deposits of gravel, sand, silt, and clay that overlie the basalt: layer 2 consists of the Saddle Mountains Basalt, layer 3 the Wanapum Basalt, and layer 4 consists of the upper thousand ft of Grande Ronde Basalt. Recharge to the groundwater system is from precipitation, leakage from streams, and seepage from surface water irrigation. Natural discharge of aquifers is principally to streams. Discharge by groundwater pumpage from the study area ranged from approximately 2,000 acre-ft in 1950 to 144,000 acre-ft in 1980. About 85% of the total pumpage in 1980 was from the Oregon part of the study area. Water level declines of over 300 ft occur locally in parts of the study area. (USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Geohydrology and digital simulation of the ground-water flow system in the Umatilla Plateau and Horse Heaven Hills area, Oregon and Washington
Series title:
Water-Resources Investigations Report
Series number:
87-4268
Edition:
-
Year Published:
1988
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
v, 72 p. :ill., maps ;28 cm.