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

Abstract

The Regional Aquifer-System Analysis (RASA) Program was started in 1978 following a congressional mandate to develop quantitative appraisals of the major ground-water systems of the United States. The RASA Program represents a systematic effort to study a number of the Nation's most important aquifer systems, which in aggregate underlie much of the country and which represent an important component of the Nation's total water supply. In general, the boundaries of these studies are identified by the hydrologic extent of each system and accordingly transcend the political subdivisions to which investigations have often arbitrarily been limited in the past. The broad objective for each study is to assemble geologic, hydrologic, and geochemical information, to analyze and develop an understanding of the system, and to develop predictive capabilities that will contribute to the effective management of the system. The use of computer simulation is an important element of the RASA studies, both to develop an understanding of the natural, undisturbed hydrologic system and the changes brought about in it by human activities, and to provide a means of predicting the regional effects of future pumping or other stresses.The final interpretive results of the RASA Program are presented in a series of U.S. Geological Survey Professional Papers that describe the geology, hydrology, and geochemistry of each regional aquifer system. Each study within the RASA Program is assigned a single Professional Paper number, and where the volume of interpretive material warrants, separate topical chapters that consider the principal elements of the investigation may be published. The series of RASA interpretive reports begins with Professional Paper 1400 and thereafter will continue in numerical sequence as the interpretive products of subsequent studies become available.

Hydrogeologic framework of the Treasure Valley and surrounding area, Idaho and Oregon

“…3) (Whitehead, 1992). Newton (1991) constructed a groundwater-flow model of the WSRP regional aquifer system that extended from the junction of Salmon Falls Creek and the Snake River to the junction of the Payette and the Snake Rivers (fig. 3).…”

“…Because the study area includes parts of the Boise and Payette River basins and lies within the WSRP defined by Newton (1991) and Whitehead, (1986Whitehead, ( , 1992) "western Snake River Plain aquifer system" is used in this report.…”

“…The USGS Snake River Plain RASA program described various aspects of the hydrogeology of the eastern and western Snake River Plain in several publications. RASA publications for the WSRP include depth to water maps (1980 conditions) (Lindholm and others, 1982;1988), a water budget (Kjelstrom, 1995), a geohydrologic framework (Whitehead, 1986(Whitehead, , 1992, a map of irrigated lands and land use (1980 conditions) (Lindholm and Goodell, 1986), and steady-state and transient MODFLOW models (Newton, 1991). Following the RASA, Maupin (1991Maupin ( ) used 1980 data to construct a composite depth-to-water map for the WSRP, including much of the study area.…”

“…Eight groundwater-flow models of all or part of the WSRP have been published with varying objectives, detail, and model extent (Cosgrove, 2010;Johnson, 2013). Three models include all or most of the current study area: those of Newton (1991), Petrich (2004a), and Johnson (2013) (fig. 3).…”

“…The studies most relevant to the current work are those of Whitehead (1986Whitehead ( , 1992, Newton (1991), Squires and others (1992), and Wood (1997b) (table 4). These authors used different approaches to delineate their hydrogeologic units: Whitehead (1986Whitehead ( , 1992 and Newton (1991) defined rock units based on lithology and age; alternatively, Squires and others (1992), and Wood (1997b) used depositional environments or facies. Whitehead (1986Whitehead ( , 1992 described the hydrogeology of both the ESRP and WSRP regional aquifer systems.…”