Comparing Snowpack Trace Chemistry to Simulated High Resolution WRF Model Precipitation Increases: Payette River Basin, Idaho

Idaho Power Company (IPC) is an investor owned utility serving over a million customers in southern Idaho and eastern Oregon. About half of the electricity delivered to IPC's customers comes from its 17 hydroelectric projects on the Snake River and its tributaries. With hydropower being such a significant component of the company's generation portfolio, snowpack is critical to IPC's hydro operations and the company has developed a winter orographic cloud seeding program targeting the Payette and Upper Snake River basins to augment the high elevation snowpack. IPC and the National Center for Atmospheric Research (NCAR) are in the middle of a multi-year study to determine precipitation enhancement due to winter orographic cloud seeding in the Payette River basin. As part of this study, a WRF cloud seeding module, developed by NCAR, will be used to estimate cloud seeding increases by simulating storms with and without seeding operations. IPC, working with Boise State University (BSU), has begun collecting samples of the snowpack in and around the Payette River Basin for trace chemistry analysis. Snow samples will be analyzed for silver and other trace elements from within and upwind of the target area. Silver concentrations will be compared with other trace element concentrations to determine if a seeding signature exists and evaluate targeting skill. Simulated precipitation increases will be compared to trace element levels in seeded and unseeded areas to evaluate the WRF cloud seeding module's performance.