A Cloudseeding Program to Increase Aquifer Outflow in Northern California's McCloud and Pit River Watersheds

Northern California's Pit and McCloud River watersheds overlay a combination of highly fractured porous, volcanic High Cascade and flood basalts. Pacific Gas and Electric Company (PG&E) is completing a project that will place 15 ground based cloud seeders in the mountains on and around Mt. Shasta. These seeders will be remotely operated and disperse heated plumes of silver iodide crystals to enhance snowfall over several hundred square miles of forested watershed. A natural lag in runoff response is expected to provide increased outflow from the springs, even during dry years when there may be a scarcity of clouds to seed. Adding additional snow to the snowpack utilizing cloudseeding is anticipated to enhance aquifer pressure increasing naturally occurring groundwater outflow from springs by as much as 9%. The increased artesian outflow is anticipated to increase the McCloud and Pit River combined runoff by 308 cubic hectometers (250,000 acre feet) or by approximately 0.35% producing approximately 330 gigawatt hours per year (GWh/year) additional hydroelectric generation. The increased runoff delivered daily throughout the year from springs can provide additional opportunity for downstream residential, agricultural, and industrial use as it passes through Shasta Lake, the Sacramento River, and eventually entering the San Francisco Bay estuary.