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DRI scientist says cloud seeding added "11,500 acre feet" to snowpack; commission hears safety and downstream concerns
Summary
Desert Research Institute meteorologist Frank McDonough told the Lander County Commission that state-run ground-based cloud seeding increased mountain snowpack and runoff; commissioners and residents asked about silver iodide and potential downstream effects. McDonough said suspension criteria and monitoring are built into the program.
Frank McDonough, a scientist and meteorologist with the Desert Research Institute, told the Lander County Commission on July 24 that Nevada's ground-based cloud-seeding program produced measurable increases in mountain snowpack and river flow.
"We in we added 11,500 acre feet to the snowpack," McDonough said while describing last winter's operations. He explained DRI runs ground generators when low, subfreezing clouds pass the target ranges and uses SNOTEL measurements and control areas to validate increases in target basins.
McDonough described operational safeguards: the program runs November 1 through April 30, suspends when snowpack exceeds 150% (140% near spring), halts on flood watches or avalanche warnings, and does not operate in blue-sky conditions. He addressed toxicity questions directly: "cloud seeding does not add free silver to the environment," he said, explaining the project releases silver iodide (an insoluble, uncharged compound) in minute quantities and that multiple studies have found no detectable accumulation above natural background.
Commissioners and attendees pressed on monitoring, regional effects and footprint. A county natural resources officer, Pam Harrington, asked whether anything other than silver iodide or carriers is released; McDonough described the generator output as a dust of silver iodide plus carbon dioxide and water vapor from the acetone carrier, and said annual silver mass released is small: "maybe the total amount of silver I've been putting up is probably on the order of 5 pounds." He said that measurement campaigns and soil-snow sampling are underway and that DRI will return with findings.
Several commissioners asked whether seeding in the Sierra Nevada reduces downstream precipitation in northeastern basins. McDonough said modeling and observational work show the effect on total passing moisture is tiny (fractions of a percent) and that mixing and large atmospheric scales make measurable downstream losses unlikely; he noted DRI compares seeded target areas to similar unseeded control areas to quantify impacts.
Why this matters: Lander County and other Humboldt-basin communities rely on winter runoff for agriculture, municipal supplies and ecosystem function. Commissioners asked about program expansion, local footprints (DRI described a generator footprint roughly 1 mile wide and up to 30 miles long), and whether the program could be extended to other mountain ranges.
Next steps: commissioners asked staff to request the DRI's seasonal validation reports and to bring DRI back when preliminary local silver and soil results are complete. McDonough told the commission he expects to present spring sampling results next season.
