Summary of a Weather Modification Feasibility Study for Winter Snowpack Augmentation in the Eastern Snake River Basin, Idaho

Abstract

North American Weather Consultants performed a feasibility/preliminary design study for a potential operational winter cloud seeding program in the Eastern Snake River Basin Program (ESRBP) in Idaho. Two potential target areas were identified. One area was located along the south slopes of the Centennial Mountains and the Lion Head and Henrys Lake Mountains in northeastern Idaho. This area is denoted as the North Target Area. The other area encompasses all or portions of the Big Hole Range, the Snake Range, the Grays Lake Mountains, and the Aspen Range in eastern Idaho. This area is denoted as the East Target area. The primary program goal would be to increase winter snowpack in the target areas through operational cloud seeding.  Average increases of 5.5% in April 1st snow water contents for the North Target area and 7.6% for the East Target Area via cloud seeding were estimated through transference of the indicated results from the Climax I and II research programs. Simulations using empirically derived snowpack streamflow relations yielded estimated average increases in March-July streamflow from two seeding modes totaling approximately 149,350 acre-feet (1.84 x 108 m3) for the combination of the two areas. The costs per acre-foot for the estimated increases in March-July combined area streamflow range from $2.95 to $4.51 per acre-foot of additional water in an average water year. A preliminary design for an operational winter cloud seeding program is described. One preliminary winter season of supercooled liquid water and lower-level temperature and wind observations is recommended to determine the presence of supercooled liquid water and low-level temperature inversions.