Central Columbia Plateau - Yakima River Basin

Science Center Objects

The Central Columbia Plateau/Yakima River Basin (CCYK) National Water-Quality Assessment (NAWQA) study unit is located in Central Washington, USA. The study unit is dominated by intensive agricultural practices, with irrigated agriculture a common practice for crop production (see study area description). Due to the intensive agriculture and irrigation, this area exhibits a number of water quality issues including high nutrient loading resulting in eutrophication, elevated concentrations of water soluble pesticides, and elevated concentrations of organochlorine compounds (e.g. DDT) in both bed sediment and fish. Given the overriding presence of agriculture and the documented effects of agricultural practices, continued work in the study unit will focus on separating out the mechanisms and effects of various agricultural management practices on ground water, surface water and stream ecosystem conditions to truly understand how natural and anthropogenic chemicals move through the hydrologic system. This information should dramatically help local, regional, state, and federal land managers produce fair and sound decisions regarding water and land management within the CCYK study area.

Central Columbia Plateau / Yakima River Basin Study Approach

During Cycle I of NAWQA, most of the work within the CCYK study unit focused on assessing the status and trends in the quality of freshwater streams and aquifers, and to provide a sound understanding of the natural and human factors that affect the quality of these resources (see Publications).

During Cycle II, most of the program's effort will be on examining water quality trends, understanding the mechanisms by which contaminants move through hydrologic systems and characterizing the potential effects of contaminants and other water-quality disturbances on humans and aquatic ecosystems. To describe water quality trends, previous surface water and groundwater sites will be re-examined to characterize decadal changes. To understand the mechanisms affecting the transport of contaminants through the hydrologic system and their potential impacts within the study unit, two topical studies will be performed. These topical studies will include the Agricultural Chemical Transport Study designed to understand the transport of agricultural chemicals through the groundwater and surface water and the Nutrient Enrichment Effects study designed to examine the response of aquatic biota to varying levels of nutrients as a result of natural and management conditions. The majority of this work will be conducted between 2002 and 2005.

The National Water-Quality Assessment Program

Since 1991, USGS scientists with the NAWQA program have been collecting and analyzing data and information in more than 50 major river basins and aquifers across the Nation. The goal is to develop long-term consistent and comparable information on streams, ground water, and aquatic ecosystems to support sound management and policy decisions. The NAWQA program is designed to answer these questions: 1. What is the condition of our Nation's streams and ground water? 2. How are these conditions changing over time? 3. How do natural features and human activities affect these conditions?

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.