USGS Washington Water Science Center
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Assessment of Groundwater in Storage, Eastern Pasco Basin, Washington
Problem - Since 1952 water diverted from the Columbia River has been used to irrigate parts of the Pasco basin in eastern Washington. As a result of the surface-water irrigation, groundwater levels generally have risen in the area. The increases in groundwater fluxes and groundwater in storage have created a need to better understand the flow system before and after the start of irrigation to assist in the management of the groundwater resources.
Objectives - The objectives for the groundwater study have been defined by a joint effort of the Washington State Department of Ecology, U.S. Bureau of Reclamation and other parties. These objectives are to: (1) define the hydrogeology of the study area, (2) determine flow patterns of the groundwater system and quantities of movement so that the effect of stresses on the system in terms of artificial recharge and groundwater withdrawals can be documented, and (3) simulate the effects of management scenarios on groundwater availability.
Approach - Data collection, hydrogeologic framework characterization, and assessment of the water resources of the Pasco basin will be conducted on a basin-wide scale and all major components of the water budget will be examined. Existing hydrologic and hydrogeologic data will be compiled and entered into the appropriate databases and those data will be analyzed to determine long-term trends in water levels and baseflows. Three dimensional basin-fill hydrogeology (sedimentary) and the long-term (predevelopment to 2007 conditions) water use and recharge components will be refined. New framework data, including the refined stratigraphy, will be incorporated into the existing USGS Columbia Plateau groundwater-flow model and changes in basin-fill groundwater storage due to existing anthropogenic stresses and potential management scenarios will be simulated. A USGS Scientific Investigations Report will be published to describe the conceptual model of the flow system and present comprehensive water budgets.