Watershed Model

The Mike SHE modeling software from DHI Water and Environment is being used as part of the technical assessment for the watershed planning process. The main goal of the modeling process is to support decision-making during development of the watershed plan. The model is intended to:

• provide water budget for the basin
• simulate surface water - aquifer interactions
• provide a "what if" tool for evaluation of effects and alternatives

The modeled area encompasses two administrative watersheds: WRIA 55 and WRIA 57. These watersheds are located just west of the Washington-Idaho Stateline and encompass more than 700 square miles. The Spokane Valley includes one of the most productive aquifers in the United Sates: the Spokane Valley-Rathdrum Prairie Aquifer. This aquifer hydraulically links WRIA 55 and WRIA 57 (see figure 1) influencing the decision to combine the planning process for the two watersheds. The Spokane Valley aquifer interacts with the Spokane River in WRIA 57 and discharges a significant amount of water into the lower Little Spokane River of WRIA 55.