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G. D. Newton

Publications and source records attributed to G. D. Newton.

9 recordsLinked to original sources
USGS1989

Geohydrology of the regional aquifer system, western Snake River plain, southwestern Idaho

A three dimensional groundwater flow model was developed to simulate steady state and nonsteady-state hydrologic conditions of the regional aquifer system in the western Snake River Plain of Idaho. Water budget analysis showed that groundwater recharge was about 1,400,000 acre-ft in 1980; groundwater pumpage was estimated to be 300,000 acre-ft. Two mass water level measurements were made in March and August 1980 to define the water table in the regional system. The model was discretized into 25 rows, 72 columns, and 3 layers. Each cell represented 4 sq mi. The model was calibrated to 1980 hydrologic conditions. Calibrated transmissivity of layer 1 (500 ft thick) ranged from 1,500 to 21,500 sq ft/day. Calibrated specific yield of unconfined aquifers was 0.10 and calibrated storage coefficient of confined aquifers ranged from 0.0004 to 0.007. The calibrated model was verified by simulating monthly water-level fluctuations for 1980. Simulated water levels matched measured levels in the Boise River Valley, but the match in other areas was poor. (USGS)

Open-File Report↗
USGS1989

Hydrology of the Oakley Fan Area, south-central Idaho

The Oakley Fan area is a broad, crescent-shaped lowland along the southern margin of the Snake River Plain in south-central Idaho. Intensive groundwater development for irrigation has resulted in rapid water-level declines and, as a consequence, designation by the State of four Critical Groundwater Areas. Principal aquifers are in limestone, rhyolite, basalt, and alluvium. Annual water-level declines range from 3 ft to about 5 ft. Recharge to the groundwater system is from infiltration of surface water used for irrigation, precipitation on the surrounding mountains, infiltration of localized runoff, and upward movement of thermal water. Groundwater pumpage during the period 1979-84 averaged 173,000 acre-ft/yr. Surface and groundwater is predominantly a calcium bicarbonate type with variable concentrations of dissolved solids. Comparisons of silica and chloride concentrations and isotopic composition of groundwater were useful in determining areal extent of aquifers and movement of groundwater. A three-dimensional mathematical model of the Oakley Fan area was developed. The aquifer system was simulated in three phases: (1) Average 1979-84 hydrologic conditions, (2) 1910 hydrologic conditions, and (3) 1910-84 hydrologic conditions. Model simulation indicated that, for the period 1945-79, subsurface outflow declined from 327,000 acre-ft/yr to 215,000 acre-ft/yr. Simulated groundwater pumpage during the period 1945-79 was 3,000,000 acre-ft; simulated change in storage was 250,000 acre-ft. Simulations with the model approximate natural conditions and probably can be used to evaluate future changes in the hydrologic system.

Idaho↗