AN UPDATE ON

Abstract: A winter orographic cloud seeding program has been conducted over the higher elevation areas of central and southern Utah for 19 winter seasons. The primary seeding mode has been ground-based, manually operated silver iodide generators located in valley and foothill locations upwind of the intended higher elevation target areas. The goal of this program is to augment naturally occurring snowfall in these higher elevation areas. Resulting augmented spring and summer streamflow is utilized for irrigation. A target/control evaluation of this program indicates approximately an average 14.6 percent increase in precipitation in the target area over that predicted from the control area precipitation. A Monte Carlo test consisting of 1,000 random draws indicates these results are significant at the 5% confidence level. 1