Scientific Investigations Report 2006–5205
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2006–5205
Surface water in the Yakima River Basin, in south-central Washington (fig. 1), is under adjudication and the amount of surface water available for appropriation is unknown, but there are increasing demands for water for municipal, fisheries, agricultural, industrial, and recreational uses. These demands must be met by ground-water withdrawals and (or) by changes in the way water resources are allocated and used. On-going activities in the basin for enhancement of fisheries and obtaining additional water for agriculture may be affected by ground-water withdrawals and by rules implemented under the Endangered Species Act for salmonids that have been either listed or were proposed for listing in the late 1990s. An integrated understanding of the ground-water flow system and its relation to the surface-water resources is needed to implement most water-resources management strategies in the basin. To obtain this understanding, a study of the Yakima River Basin aquifer system began in June 2000. The study is a cooperative effort of the U.S. Geological Survey (USGS), Bureau of Reclamation (Reclamation), the Yakama Nation (YN), and the Washington State Department of Ecology (WaDOE).
The objectives of the study as a whole are to fully describe the ground-water flow system and its interaction with and relation to surface water, and provide baseline information for a management tool—a numerical model. The conceptual model of the flow system and the results of the study will be used to guide and support actions taken by management agencies with respect to ground-water availability and to provide information to other stakeholders and interested parties. The numerical model will be developed as an integrated tool to assess short-term to long-term management activities, including the testing of potential management strategies.
The study includes three phases. The first phase includes (1) project planning and coordination, (2) compiling, documenting, and assessing available data, and (3) initial data collection. The second phase consists of data collection to support the following Phase 2 work elements: (1) mapping of hydrogeologic units, (2) estimating ground-water pumpage, (3) developing estimates of ground-water recharge, (4) assessing ground water-surface water interchanges, and (5) constructing maps of ground-water levels. Together, these five elements provide the information needed to describe the ground-water flow system, the conceptual model, and provide the building blocks for the hydrogeologic framework. In the third phase, six structural basin models and one regional model of the ground-water flow system will be constructed in order to integrate the available information. The numerical models will be used to gain a further understanding of the flow system and its relation to surface water, and to test management strategies. The models will be developed and maintained in such a fashion that they will be available and open to others.
The results from selected work elements will be described in a series of reports. This report describes the estimates of ground-water pumpage from the Yakima River Basin aquifer system, a Phase 2 work element. The Introduction and Description of Study Area sections of this report are common to most reports for the other elements of the larger study.