Tetra Tech Nitrate Mapping
To aid in the targeting of nonpoint source pollution reduction measures, this project supports the development of a groundwater contour mapping modeling tool in the Lower Yakima Valley, utilizing existing ambient groundwater data collected from July 2021 through June 2022 by the Washington State Department of Ecology (Ecology). Groundwater contour mapping increases the visible connection between land use practices on the surface and groundwater recharge, including nitrate contamination, and allows growers to observe the potential radius of their fields’ influence and for stakeholders to identify influences that are up-gradient of the wells. Developing a model for mapping groundwater elevations and nitrate concentrations provides partners with a valuable tool for tracking changes in nitrate concentrations in relation to management measures used. This methodology document summarizes the available data sources and the methodology for developing the groundwater contour mapping tool.