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Central Columbia Plateau - Yakima River Basin

Project Summaries

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4751-9BI-39 - National Water-Quality Assessment (NAWQA), Central Columbia Plateau-Yakima River Basin

Problem - The quality of the Nation's waters is highly variable and greatly influenced by the activities of man. The existing quality of the Nation's waters and the cause and effect influences from man's activities must be well understood to manage water resources to their maximum beneficial uses, while at the same time preserving the viability of aquatic ecosystems. The USGS National Water Quality Assessment (NAWQA) Program is a nationwide study to provide to Congress, the public, and water-resources managers with consistent, scientifically defensible water-quality data and interpretation of significant water-quality processes that will allow them to identify existing and emerging water-quality issues and to make more informed water-resources decisions.

The USGS will investigate water-quality issues of national and local importance within the area formed by joining two study units, the Central Columbia Plateau and Yakima River Basin, both which were studied during the first cycle of the NAWQA Program. The combined area contains some of the most productive agricultural land in the United States, and much was learned about the effects of agricultural practices on water quality during first study cycle. In the combined study, which is referred to as Cycle-II, research will focus more on how agricultural practices affect water quality because much of the ambient water quality was defined during Cycle-I.

Major issues to be addressed include 1) understanding the effects of pesticides and other contaminants on aquatic biota, 2) predicting how reductions in inputs of pesticides and nutrients to surface waters affect their concentrations at downstream locations, 3) determining the pathways by which nutrients and pesticides are entering surface waters via the ground-water system, and 4) understanding how the implementation of agricultural management practices affects water quality.

Objectives - The long-term goals of the Central Columbia Plateau-Yakima River Basin NAWQA study are to provide a nationally consistent description of current water-quality conditions in the Study Unit, define long-term trends (or lack of trends) in water quality, and identify, describe, and explain, insofar as possible, the major factors that affect observed water-quality conditions and trends.

Relevance and Benefits - An important part of the USGS mission is to provide scientific information to manage the water resources of the Nation. To help assess the Nation's water resources, the USGS established the National Water-Quality Assessment (NAWQA) Program to (1) describe the status and trends in the quality of a large, representative part of the Nation's surface-water and ground-water resources using nationally consistent methods and approaches; (2) provide an improved understanding of the primary natural and human factors affecting these conditions; and (3) provide information that supports development and evaluation of management, regulatory, and monitoring decisions by other federal, state and local agencies. Three major program elements contribute to accomplishing the goals of the NAWQA Program: (1) investigations of major river basins and aquifer systems, referred to as study units; (2) regional and national syntheses of key findings from study-unit investigations and existing information related to important water-quality topics such as pesticides, nutrients, volatile organic compounds, trace elements, and ecology; and (3) coordination at local, State, regional, and national levels with environmental and natural resource managers and other users of water-quality information. The data and information provided by the NAWQA Project in this State are vital to the NAWQA Program nationwide.

Approach - To adequately address water-quality issues at the national scale, an integrated program of water-resources investigations that is consistent at all scales is required. In contrast with many previous water-quality studies, we will analyze loads as well as concentrations of chemical constituents in order to help assess the impact of the chemicals resulting from natural processes or man-made effects. We will consider seasonal variations both from the standpoint of climate and agricultural practices. In order to determine the mechanisms causing water-quality degradation, we will search for areas with nearly homogeneous land-use and hydrologic conditions where the incoming and outflowing water quality can be compared.

WA321 - National Water-Quality Assessment Program, Surface Water Phase - Pilot Study in the Pacific Northwest District - Completed FY1992

Problem - The National Water-Quality Assessment (NAWQA) program is intended to integrate investigations of surface water (SW), ground water (GW), and precipitation with special emphasis on drinking-water sources; the program calls for a national perspective on SW and GW by studying hydrologic units scattered around the Nation, which in aggregate account for a large percentage of the Nation's water use. This pilot study on the SW phase of NAWQA is centered on the Yakima River basin which has a drainage area of 6,200 square miles and about 1,900 miles of perennial streams. Land use is dominated by forest and grazing lands near the headwaters and by 500,000 acres of irrigated agriculture in the Yakima and Kittitas Valleys. The average annual diversion for irrigation is about 80 percent of total runoff; at times, however, up to 99 percent of the flow is diverted, leaving little water in some reaches.

Objectives - To implement the National Water Quality Assessment (NAWQA) program in a test area. This requires that specific details of program implementation regarding site selection, data collection and analysis, and interpretation of results be analyzed and reported on. The purpose of this study is to provide the U.S. Geological Survey (USGS) Water Resources Division headquarters with timely results on the identifying methodology used so that guidelines may be established fo r expanding the NAWQA program in FY87.

Approach - The study includes three basic approaches: (1) fixed-frequency data collection with additional sampling to cover high flows; (2) synoptic studies of varying nature; and perhaps (3) intensive river-reach studies. The fixed station density will be greater than what may be used in normal basin coverage to allow clarification of minimum levels of density. Synoptic sampling will cover multiple parameters pointed toward problems identification done in temporal sets to assess benefit of repetitive sampling. Sampling will be augmented by detailed examination of all existing land use, pollutant discharge, and water-quality data available. A comprehensive report on basic water quality (QW) will be prepared continuously through the project (copies of current drafts will be released each quarter for administrative information/revi ew). All QW data will be stored in INFO and digitized using ARC software.

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