USGS Washington Water Science Center
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The Cycle I of the National Water Quality Assessment (NAWQA) Program conducted in the Central Columbia Plateau (CCPT) and the Yakima River Basin (YAKI) (see map) produced valuable data and many innovative and important reports used by local, state and federal agencies (see Publications). As of 2001, CCPT and the YAKI Study Units were combined to form the Central Columbia Plateau / Yakima River Basin (CCYK) Study Unit.
The CCPT and YAKI share many features including environmental setting, land use, and water quality issues. These two areas are predominantly arid systems with a high percentage of their land area within the Columbia Basin Ecoregion. Both areas are dominated by intensive agricultural practices, with irrigated agriculture a common practice for crop production. Because these systems are influenced by agriculture, they also share many of the same water quality issues. Similar water quality issues include 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, it seems only natural that the Cycle II CCYK should focus on separating out the mechanisms and effects of various agricultural practices and their associated Best Management Practices (BMPs) on ground water, surface water and stream ecosystem conditions.
However, while both systems have extensive agriculture, the two systems differ in several ways. First, the Columbia Plateau irrigation system is highly fragmented in that water is imported via canals onto the plateau where it moves through numerous, non-connected surface water systems.
In contrast, the Yakima is a single river system with a large portion of the irrigation water originating from, and returning to, the mainstem of the river.
Second, because the CCPT irrigation system is primarily artificial, stream habitat is highly variable from stream to stream; whereas, in the Yakima River Basin stream sites can be selected from a wide range of conditions with similar habitat. Third, while the Columbia Plateau and Yakima areas both contain extensive irrigated agriculture, they differ substantially in irrigation methods, water source, and crops. The similarities and the differences between the two basins and the continued dominance of both basins by agricultural land use will provide a unique opportunity to address the goals of Cycle II NAWQA and provide the information 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.