Environmental Setting of the Granger Drain and DR2 Basins, Washington, 2003-04

Abstract

The Granger Drain and DR2 basins are located in the Yakima River basin in south central Washington. These agricultural basins are one of five areas in the United States selected for study as part of the National Water-Quality Assessment Program Agricultural Chemicals: Source, Transport, and Fate Study. The Program is designed to describe water-quality conditions and trends based on representative surfaceand ground-water resources across the Nation. The objective of the Agricultural Chemicals topical study is to investigate the sources, transport, and fate of selected agricultural chemicals in a variety of agriculturally diverse environmental settings. The Granger Drain and DR2 basins were selected for the Agricultural Chemicals topical study because they represent the irrigated agricultural setting that characterizes eastern Washington. These basins are located in one of the most productive agricultural areas in the United States. This report describes the environmental setting of the Granger Drain and DR2 basins in the context of how agricultural practices, including agricultural chemical applications and irrigation methods, interface with natural settings and hydrologic processes. Introduction The Granger Drain and DR2 basins are located in the Yakima River basin in south central Washington (fig. 1). These agricultural basins are one of five areas in the United States selected for study as part of the National Water-Quality Assessment Program (NAWQA) Agricultural Chemicals: Source, Transport, and Fate Study (ACT). These basins are located in one of the most productive agricultural areas in the United States. As in many agricultural areas, crop production, pastures, and animal feeding operations in the Granger Drain and DR2 basins have been identified as sources of chemical contamination for surface and ground water in the area (Morace and McKenzie, 2002). To improve our understanding of how agricultural chemicals move through the environment and ways to best manage these chemicals, intensive chemical studies within the Granger Drain and DR2 basins were begun in 2001. Chemical samples were collected from all major hydrologic compartments within these basins, including the atmosphere, the subsurface unsaturated zone, ground water, overland flow, surface water, and the streambed surface-water/ ground-water interface. This report details the environmental setting within Granger Drain and DR2 basins. The information presented here is intended for scientists and managers working in these and similar basins and provides a context in which to evaluate current and future work conducted as part of the NAWQA program in these basins. Purpose and Scope The purpose of this report is to present an overview of the current environmental setting of the Granger Drain and DR2 basins and identify factors influencing water quality in these basins. The environmental factors described here include the natural factors of physiography, geology, soils, hydrology, and climate, and the cultural factors of population and land use. This report largely represents a compilation of the results of selected water-quality studies and existing data with respect to the environmental factors in these basins. However, some new data are presented on land use and pesticide application rates. Environmental Setting of Granger Drain and DR2 Basins The Granger Drain and DR2 basins are located in south central Washington State. The study area is bounded on the south by the Yakima River and Snipes Mountain and on the north by the Rattlesnake Hills (fig. 1). Granger Drain basin includes about 62 mi, and the DR2 basin, nested within the Granger Drain basin, has a drainage area of 2.1 mi (fig. 1). Because the region lies in the rain shadow east of the Cascade Mountains, it receives about 7 in. of precipitation per year (Western Regional Climate Center, 2005). The city of Granger, a community of about 2,500 people, is in the southwest part of the basin. Agriculture is the primary economic activity in these basins. The area was selected for this study because environmental conditions and agricultural practices are similar to other parts of the lower Yakima River basin. Environmental Setting of the Granger Drain and DR2 Basins, Washington, 2003–04 By Karen L. Payne, Henry M. Johnson, and Robert W. Black