Search USGS⌕ Search

Geology topics

S. C. Kahle

Publications and source records attributed to S. C. Kahle.

4 recordsLinked to original sources
USGS2015

Groundwater availability of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho

The Columbia Plateau Regional Aquifer System (CPRAS) covers about 44,000 square miles of southeastern Washington, northeastern Oregon, and western Idaho. The area supports a $6-billion per year agricultural industry, leading the Nation in production of apples, hops, and eight other commodities. Groundwater pumpage and surface-water diversions supply water to croplands that account for about 5 percent of the Nation’s irrigated lands. Groundwater also is the primary source of drinking water for the more than 1.3 million people in the study area. Increasing competitive demands for water for municipal, fisheries/ecosystems, agricultural, domestic, hydropower, and recreational uses must be met by additional groundwater withdrawals and (or) by changes in the way water resources are allocated and used throughout the hydrologic system. As of 2014, most surface-water resources in the study area were either over allocated or fully appropriated, especially during the dry summer season. In response to continued competition for water, numerous water-management activities and concerns have gained prominence: water conservation, conjunctive use, artificial recharge, hydrologic implications of land-use change, pumpage effects on streamflow, and effects of climate variability and change. An integrated understanding of the hydrologic system is important in order to implement effective water-resource management strategies that address these concerns. To provide information to stakeholders involved in water-management activities, the U.S. Geological Survey (USGS) Groundwater Resources Program assessed the groundwater availability as part of a national study of regional systems (U.S. Geological Survey, 2008). The CPRAS assessment includes: The present status of groundwater resources, How these resources have changed over time, and Development and application of tools to estimate system responses to stresses from future uses and climate variability and change. This effort builds on previous investigations, especially the USGS Columbia Plateau Regional Aquifer-System Analysis study (CP-RASA). A major product of this new assessment is a numerical groundwater-flow model of the system. The model was used to estimate water-budget components of the hydrogeologic units composing the groundwater system, and to evaluate groundwater availability under existing land- and water-use conditions and a possible future climate scenario representing an increase in pumpage demand due to a warming climate. Information from this study also allowed for analysis of: The CPRAS for predevelopment times (pre-1920), Variations from 1920 through 2007, Conditions during 1985–2007 (referred to as “existing conditions”), and Changes in the system from predevelopment times. The model also is a useful tool for investigating water supply, water demand, management strategies, groundwater-surface water exchanges, and potential effects of changing climate on the hydrologic system.

Idaho, Oregon, Washington↗
USGS2011

Hydrogeologic framework and hydrologic budget components of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho

The Columbia Plateau Regional Aquifer System (CPRAS) covers an area of about 44,000 square miles in a structural and topographic basin within the drainage of the Columbia River in Washington, Oregon, and Idaho. The primary aquifers are basalts of the Columbia River Basalt Group (CRBG) and overlying sediment. Eighty percent of the groundwater use in the study area is for irrigation, in support of a $6 billion per year agricultural economy. Water-resources issues in the Columbia Plateau include competing agricultural, domestic, and environmental demands. Groundwater levels were measured in 470 wells in 1984 and 2009; water levels declined in 83 percent of the wells, and declines greater than 25 feet were measured in 29 percent of the wells. Conceptually, the system is a series of productive basalt aquifers consisting of permeable interflow zones separated by less permeable flow interiors; in places, sedimentary aquifers overly the basalts. The aquifer system of the CPRAS includes seven hydrogeologic units-the overburden aquifer, three aquifer units in the permeable basalt rock, two confining units, and a basement confining unit. The overburden aquifer includes alluvial and colluvial valley-fill deposits; the three basalt units are the Saddle Mountains, Wanapum, and Grande Ronde Basalts and their intercalated sediments. The confining units are equivalent to the Saddle Mountains-Wanapum and Wanapum-Grande Ronde interbeds, referred to in this study as the Mabton and Vantage Interbeds, respectively. The basement confining unit, referred to as Older Bedrock, consists of pre-CRBG rocks that generally have much lower permeabilities than the basalts and are considered the base of the regional flow system. Based on specific-capacity data, median horizontal hydraulic conductivity (Kh) values for the overburden, basalt units, and bedrock are 161, 70, and 6 feet per day, respectively. Analysis of oxygen isotopes in water and carbon isotopes in dissolved inorganic carbon from groundwater samples indicates that groundwater in the CPRAS ranges in age from modern (<50 years) to Pleistocene (>10,000 years). The oldest groundwater resides in deep, downgradient locations indicating that groundwater movement and replenishment in parts of this regional aquifer system have operated on long timescales under past natural conditions, which is consistent with the length and depth of long flow paths in the system. The mean annual recharge from infiltration of precipitation for the 23-year period 1985-2007 was estimated to be 4.6 inches per year (14,980 cubic feet per second) using a polynomial regression equation based on annual precipitation and the results of recharge modeling done in the 1980s. A regional-scale hydrologic budget was developed using a monthly SOil WATer (SOWAT) Balance model to estimate irrigation-water demand, groundwater flux (recharge or discharge), direct runoff, and soil moisture within irrigated areas. Mean monthly irrigation throughout the study area peaks in July at 1.6 million acre-feet (MAF), of which 0.45 and 1.15 MAF are from groundwater and surface-water sources, respectively. Annual irrigation water use in the study area averaged 5.3 MAF during the period 1985-2007, with 1.4 MAF (or 26 percent) supplied from groundwater and 3.9 MAF supplied from surface water. Mean annual recharge from irrigation return flow in the study area was 4.2 MAF (1985-2007) with 2.1 MAF (50 percent) occurring within the predominately surface-water irrigated regions of the study area. Annual groundwater-use estimates were made for public supply, self-supplied domestic, industrial, and other uses for the period 1984 through 2009. Public supply groundwater use within the study area increased from 200,600 acre-feet per year (acre-ft/yr) in 1984 to 269,100 acre-ft/yr in 2009. Domestic self-supplied groundwater use increased from 54,580 acre-ft/yr in 1984 to 71,160 acre-ft/yr in 2009. Industrial groundwater use decreased from 53,390 acre-ft/yr in 1984 t

Scientific Investigations Report↗
USGS1995

Geohydrology and ground-water quality of east King County, Washington

East King County is a 250-square-mile area east of Seattle underlain by as much as 1,200 feet of unconsolidated deposits of glacial and nonglacial origin. A surficial geology map and 12 geohydrologic sections were constructed and used to delineate 10 geohydrologic units, 4 of which are major aquifers. Annual precipitation over the study area averages 57 inches, of which 31 inches, or 413,000 acre-feet, enter the ground-water system as recharge. Some 98,500 acre-feet of ground water is estimated to discharge to surface water bodies each year, 9,540 acre-feet is discharged through springs, and 4,270 acre-feet is withdrawn from wells. The chemical quality of the ground water in east King County is typical of that in other areas of western Washington. The median dissolved-solids concen- tration of 124 samples analyzed was 115 milligrams per liter, and 95 percent of the water samples were classified as soft or moderately hard. The median nitrate concentration was 0.07 milligrams per liter, and no widespread nitrate contamination was apparent.

Water-Resources Investigations Report↗