Design of a Ground Based Snowpack Enhancement Program using Liquid Propane

David W Reynolds

Abstract


The design of a winter snowpack augmentation program utilizing liquid propane as the seeding agent is described. The program has been designed utilizing results from the Sierra Cooperative Pilot Project (SCPP). Observations from SCPP showed that the bulk of the supercooled liquid water (SLW) in winter storms over the Sierra occurs within the first kilometer above the barrier at temperatures between 0 and -10°C and in concentrations of 0.05 to 0.2 g/m^3. Mountain-top icing stations within the Feather River drainage indicate that icing occurs with a mean temperature near -3°C. These results imply the need for a seeding agent capable of converting the SLW to ice crystals at fairly warm temperatures and be released remotely from the ground. Liquid propane meets these requirements. The design calls for two 2175 liter tanks of propane at each site. Remote operation will be via radio to an on-site micro-processor. Site seperation will be every two kilometers along the crest of the Sierra above the Middle Fork Feather. Tanks will be flown in by helicopter in the fall and removed early in the spring. Three sites will be used the first year for test purposes. The release rate will be 10 liters/hr per dispenser. Multiple atmospheric soundings, telemetered mountain-top icing data, and a simple diagnostic targeting model will be used for real-time decision making. Initial estimates are that suitable clouds exist from 200 to 400 hours per winter season. Based on propane activitation levels, cloud liquid water content, and crystal growth times, 12,300 m^3 per dispenser per hour is possible.

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