Weather Modification Research to Enhance Water Supplies in the Western United States (Invited Presentation)

The US Bureau of Reclamation’s mission from it’s founding in 1905 was to reclaim the West from the arid desert to provide beneficial water for farmers, ranchers, and municipalities. It developed over 450 large clean hydropower dams to meet this goal by working with stakeholders across the West. This paper briefly describes the motivation, scientific evolution and results of Reclamation’s weather modification projects to enhance water supplies.

In the 1962 after the extreme drought of the 1950s, the Bureau established Project Skywater to augment surface water supplies through applied weather modification research. This program was under the auspices of the Division of Atmospheric Water Resources Management (DAWRM) at Reclamation’s Engineering and Research Center in Denver led by Dr. Archie Kahan until 1983 and then by Dr. Bernie Silverman. At first DAWRM had a team of engineers and scientists who monitored applied R&D contracts in cloud and precipitation physics, nucleation, transport and diffusion of seeding materials, statistical evaluation procedures, experimental design, environmental impacts and legal aspects at various universities and private research companies across the West.

In the 1970s Reclamation expanded its internal R&D capabilities by hiring more research meteorologists to conduct research with its contractors and operate field projects to understand the physics and demonstrate the effects of weather modification to augment precipitation. The initial focus was on winter orographic clouds in mountains which supplied 80-90 % of the flow into Reclamation’s reservoirs, later summer convective precipitation was added. Early projects included the Park Range Experiment, Colorado River Basin Pilot Project, and the Climax Experiment. Major field projects followed in the Sierra - Sierra Cooperative Pilot Project, and in the High Plains studying convection from Montana to Texas - High Plains Experiment. Field observations on Grand Mesa, Colorado provided physical measurements of microphysical properties of precipitation and AgI, thus establishing the physical direct detection of seeding effects. Similar research was conducted by Reclamation scientists on the Wasatch Plateau of central Utah in cooperation with the Utah-NOAA cooperative program.

Dr. Bernie Silverman joined Reclamation in 1973 and led the R&D efforts in the mid-1970s and 1980s. His emphasis was on bringing the numerical modeling and observational scientists together to improve the analysis and prediction of seeding and precipitation enhancement effects. Through many workshops in the US and with international scientists in Europe, these two different scientific teams worked together to validate and improve numerical models and our physical understanding.

USAID, at the request of King Mohamad V of Morocco, funded Program Al Ghait - The Morocco Snowpack Augmentation Project from 1984-1989 at $5,000,000. This project transferred winter orographic cloud seeding technology from the California Sierra Nevada to the High Atlas of Morocco. Scientific methodology, training, and equipment from a radar and rawinsonde system to cloud physics aircraft instruments and observations were provided by American companies and university and Reclamation scientists. Results were deemed positive by the Moroccan meteorologists; however, statistical significance was not yet achieved. The project collaborated with Moroccan agencies in agriculture, hydropower production, and economics to assess its potential benefits. USAID funded a similar project in Thailand at the request of King Bhumibol. This project focused on warm rain processes and deep convective clouds using AgI seeding. The 1987-89 project was too short to develop statistically significant results.

One of the most important results of Reclamation’s research was the improvement of scientific research teams and development of new cloud and precipitation physics experts, who received advanced degrees through Reclamation’s applied R&D contracts. Dozens of MS and PhD level students, who have now gone on to be leaders in their fields, had their roots within Project Skywater and related projects. Many of theses names now appear on the list of AMS Fellows. However, the statistically significant proof that weather modification enhanced precipitation and runoff remained elusive according to the National Research Council as late as 2003. Project Skywater funding ended in 1988; however, through earmarked write-in funds and collaboration with NOAA’s Weather Damage Mitigation Program (WDMP) limited research continued until the mid-2000s.