A Level II Weather Modification Feasibility Study for Winter Snowpack Augmentation in the Salt River and Wyoming Ranges in Wyoming

Don A Griffith, Mark E Solak, David P Yorty, Bruce Brinkman


North American Weather Consultants performed a feasibility/preliminary design study for a potential operational winter cloud seeding program for the Salt River/Wyoming Ranges in Wyoming, under contract to the Wyoming Water Development Commission. The Desert Research Institute (DRI) conducted atmospheric modeling as part of this study. The primary project goal is to increase winter snowpack in the target area through operational cloud seeding. An average increase of 10% in November through March precipitation via cloud seeding was calculated, using results from the Climax I and II research programs. Simulations using empirically derived snowpack-streamflow relations yielded increases in streamflow from three seeding modes totaling approximately 109,500 acre feet (1.35 x 10^8 m^3) on average. The costs per acre foot for the estimated increases in streamflow range from $1.91 to $7.13 per acre foot of additional water and associated benefit/cost ratios range from 5.8/1 to 1.6/1, depending on the seeding mode(s). 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 frequency of low-level temperature inversions during seedable periods. The DRI case study modeling results indicated that such inversions could inhibit the effectiveness of low elevation ground based seeding releases.

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