Cloud Seeding History: Looking Back at the Colorado River Basin Pilot Project
Posted on August 8, 2025 by curryja
by Art Rangno
How we fooled ourselves about the effectiveness of cloud seeding.
The Colorado River Basin Pilot Project (CRBPP, 1970-75) is still the most ambitious, expensive randomized orographic cloud seeding project in US history. It featured an unprecedented amount of instrumentation, including up to 87 recording gauges, telemetered high-altitude weather stations, some above the tree line, telemetered seeding generators, radars, and, later, aircraft measurements. The target area in the San Juan Mountains of SW Colorado was over 1200 square miles (~3100 km2). Avalanche hazards and snowpack were closely monitored, with additional support from the Soil Conservation Service and the US Geological Survey.
An independent contractor who did not know whether days were seeded or not, measured precipitation. Simultaneously during the CRBPP, research was underway due to a separate million dollar grant to explore possible ecological impacts of the extra snow that was expected to be produced and the possible effects of silver iodide being used to seed.
The CRBPP aimed to demonstrate at a high level of competence that cloud seeding could increase snowfall on a determinant basis. It was going to be the centerpiece of all the Bureau of Reclamation’s cloud seeding efforts, one even having its own documentary film, “Mountain Skywater,” a testimony to the CRBPP’s perceived importance. Obtaining a statistically significant result that seeding had increased snowfall would then support widespread operational seeding after the CRBPP to address looming water shortages in the West.
https://judithcurry.com/2025/08/08/cloud-seeding-history-looking-back-at-the-colorado-river-basin-pilot-project/
