A Winter Operational Cloud Seeding Program: Upper Gunnison River Basin, Colorado

Don A. Griffith, David P. Yorty, Mark E. Solak


A winter orographic cloud seeding program has been conducted in the Gunnison, Colorado region for the past eight winter seasons. The intended target area is elevations above 9,000 feet MSL that provide streamflow to Blue Mesa Resevoir located in western Gunnison County. The goal of this operational program has been to augment higher elevation winter snowpack, which subsequently contributes to spring and summer sreamflow.  This program has operated under permits granted by a number of local entities and it has also recieved some funding support from the Colorado Water Conservation Board. The program is supported by a number of local entities and it has also received some funding support from the Colorado Water Conservation Board and the three Lower Colorado river basin States (Arizona, California and Nevada). A network of 20-25 ground based silver iodide generators has been used to seed all storm periods thought to represent good seeding opportunities based upon targeting considerations and the likely presence of supercooled liquid water. An historical target/control evaluation technique, was developed, based upon NRCS SNOTEL April 1st snow water content observations, to provide estimates of the potential effects of cloud seeding. These estimates indicate average seasonal increases in the 10-15% range. Calculations were made of increases in April through July sreamflow based upon the indicated increases in April 1st snow water contents. Increases in the range of 79,600 to 96,200 acre-feet in an average April - July runoff were indicated based upon a 10% increase in April 1st snow water content for an average winter season. Costs of producing the augmented runoff based upon these calculated increases in streamflow ranged from $0.94 to $1.13 per acre-foot.

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