Yakima River Basin

9722-A4W - Ground Water in the Yakima River Basin, Washington, and its Relation to the Surface-Water Resource - Completed FY2011

Problem and Needs - The surface water in the Yakima River Basin is under adjudication and it is not known how much is available for appropriation. There are increasing demands for water for municipal, fisheries, agricultural, industrial, and recreational uses which 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 to enhance fisheries and to obtain additional water for agriculture may be affected by ground-water withdrawals and by rules implemented under the Endangered Species Act for salmonid fish. 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.

Objectives - The objectives of the study are to describe the ground-water flow system and its interaction with surface water, and to integrate this information into a water-resources management tool--a numerical model. The improved understanding of the system can be used to describe concepts to laypersons and to guide and support actions taken by natural-resources management agencies. The numerical model will be an integrated tool for daily to long-term water-resources management and for testing potential management strategies

Relevance and Benefits - The study addresses many issues identified in the USGS Water Resources Division's strategic plan for meeting the Nation's water-resources needs. They include the development of tools for managing the Nation's watersheds effectively and the improvement of existing simulation tools. Other important issues include the assessment of availability and sustainability of America's water, estimating effects of land-use and management alternatives on water quantity, and determining effects of ground-water withdrawals on surface water and aquatic ecology. The USGS is a neutral scientific party that provides information and develops models to solve important problems that are common in the Nation.

Approach - The study will be conducted in three phases. The first phase includes: (1) project planning and coordination, (2) gathering, compiling, documenting, and assessing available data, and (3) collecting initial data. The second phase consists of data-collection activities to support: (1) mapping of hydrogeologic units, (2) estimating ground-water use, (3) developing estimates of ground-water recharge, and (4) constructing maps of ground-water levels. Together, these four work elements provide the information for an overall description of the ground-water flow system and the building blocks for the hydrogeologic framework. In the third phase, a numerical model or models will be constructed of the ground-water flow system to integrate the available information. The model will be used to gain an understanding of the flow system and its relation to surface water, and to test management strategies. The model will be available for public use.