Simulated Hydrologic Impacts of Cloud Seeding in the North Platte and Little Snake River Basins of Wyoming

In the western United States, the recent mega-drought and impacts of climate change have resulted in an interest in cloud seeding to enhance water supplies. Studies and field campaigns focused on cloud seeding across the West have quantified the effect on precipitation generation through the release of silver iodide, and these effects can be studied in simulations using WRF-WxMod^®, a modeling capability based on the WRF model that includes a cloud-seeding parameterization. Here, we use a 36-member ensemble of WRF-WxMod simulations to force a spatially distributed hydrological model, WRF-Hydro, to study how simulated cloud seeding impacts hydrology in the North Platte and Little Snake River basins of Wyoming during the 2020 water year. WRF-Hydro is configured with a 1-km land surface model, Noah-MP, with the terrain routing grid run at 250 m. Compared to observations, WRF-Hydro shows good performance with an average Kling Gupta Efficiency = 0.80. Over the 2020 water year, snow water equivalent increases by 10 mm over target mountain ranges due to simulated cloud seeding and streamflow increases by 6,921 acre-ft over the entire domain. A water budget analysis shows that increases in ensemble mean precipitation due to simulated cloud seeding result in 78% diverted to increasing streamflow, 21% increasing soil moisture, and 8% going toward evapotranspiration. Such information is critical for water managers looking into the efficacy of cloud seeding to enhance their water resources amidst climate change.