Summary of a Weather Modification Feasibility/Design Study for Winter Snowpack Augmentation in the Upper Boise River Basin, Idaho
North American Weather Consultants (NAWC) performed a feasibility/preliminary design study of potential means of augmenting an existing operational winter cloud seeding program in the Upper Boise River Basin (UBRB) program in Idaho by extending the base project period of November through March by one month (April) and possibly adding remote generators and seeding aircraft to the existing lower elevation manual generator network. This study was performed for the Idaho Water Resources Board (IWRB). The IWRB noted that the upper Boise, including the North Middle and South Forks, and Mores Creek supplies 90% of the water for the lower Boise Basin. The UBRB ranges in elevation from approximately 915 m (3,000 feet) MSL at Lucky Peak Dam to crest elevations of approximately 2590 – 2700 m (8,500 to 9,500 feet) MSL between the Boise River and Big Wood River Basins. NAWC recommended that the intended target area for the UBRB program be defined as those regions in the basin that are above 1524 m (5,000 feet) MSL. The primary program goal would be to increase winter snowpack in the target area through operational cloud seeding. The resulting augmented spring and summer stream flow would be used in a number of ways including augmented hydroelectric power production and agricultural irrigation.
Average increases of 4.7% in April 1st snow water contents from cloud seeding were estimated through transference of the indicated results from the Climax I and II research programs. Simulations using empirically derived snowpack-stream flow relations yielded estimated average increases in March-July stream flow from three seeding modes totaling approximately 1.004 x 108 m3 (81,425 acre-feet). The costs of the estimated increases in March-July stream flow range from $0.003 to $0.01 per cubic meter ($3.29 to $12.45 per acre-foot) of additional water in an average water year. A preliminary design for an augmented operational winter cloud seeding program is described.