Federal support for cloud seeding research has generally declined since the mid-1970s. Nevertheless, several parties and states in the Colorado River basin maintain a strong interest in the prospects of cloud seeding to increase precipitation. For example, in a 2005 letter to the Secretary of the Interior, the Governor’s Representatives on Colorado River Operations sought to work with the Department of the Interior “to implement a precipitation management (cloud seeding) program in the basin (both Upper and Lower)” (Governors, 2005). In light of the stress on federal funding for discretionary expenditures, a renewed large-scale, federally led weather modification initiative does not appear likely (AAAS, 2006). For the foreseeable future, weather modification experiments and operations will depend mainly on funding from state governments, local communities, and private-sector entities (e.g., utility companies).

Six of the seven Colorado River basin states presently support some type of precipitation or snowpack augmentation operations (WMA, 2005). The most prominent cloud seeding project in the basin may be one sponsored by the Wyoming Water Development Commission. This 5-year project is designed to demonstrate if rainfall and snowpack in the state’s mountainous regions can be enhanced (see http://www.rap.ucar.edu/projects/wyoming/). Cloud seeding operations are planned in the Wind River Mountains and the Medicine Bow Range/Sierra Madre Mountains. The program is important because of its potential scientific and operational evaluation for the Colorado River basin states and because the 5-year program is to utilize a solid scientific base for the experiments. If the Wyoming pilot trials increase snowpack by 10 percent, the additional yield would, on average, be on the order of 130,000 to 260,000 acre-feet of additional runoff each spring (WWDC, 2006), which would represent a notable increase in water supplies. In addition to the Colorado River basin states, entities such as municipalities and the ski industry are interested in the prospects of augmenting water supplies and snowpacks by cloud seeding. Denver Water, for example, commenced cloud seeding again in 2002 after 20 years of putting its program on hold. Denver Water’s cloud seeding program was reinitiated as a response to the 2002 drought and was conducted through March 2003 (see http://www.denverwater.org/cloud_seeding.html).

In evaluating the success or benefits of cloud seeding operations, the experience of six decades of experiments and applications that failed to produce clear evidence that cloud seeding can reliably en-