Relating Snowpack and Snowmelt in Weather Modified Watersheds

A 2008 editorial in Natureentitled “Change in the weather,” it is stated that “a renewed push for scientific research into weather-modification technologies is long overdue.” The editorial continues with “Today's rain-makers struggle with their own credibility issues. They do have well established methods for seeding clouds….. weather-modification supporters face a perceived negative bias in the scientific community….. There has yet to be the definitive experiment that settles exactly how well cloud seeding… works (or not).” The editorial concludes with “Other countries, such as the United States, have simply given up; the most promising experiment in America is run not by the federal government but by the state of Wyoming....which is being evaluated by experts from the National Center for Atmospheric Research (NCAR). That's the type of targeted and rigorous study that needs to be done in weather modification, but it took Wyoming to do it.”

The motivation for weather modification operations is to increase water supply (streamflow) due to increased snowpack. NCAR will complete their evaluation in Fall 2014 that will provide, with uncertainty, the anticipated increase (percent) in snowpack due to cloud seeding. The majority of the cloud seeding for the Wyoming Weather Modification Pilot Project was performed in the North Platte River Basin (NPRB). Researchers from the University of Wyoming, in cooperation with NCAR, analyzed historic meteorological data for the cloud seeding season (November 15^th to April 15^th) for eight years (2001-2008) to determine “seedable” periods. Using this data combined with the anticipated increase (percent with uncertainty), University of Alabama researchers developed two models (statistical and hydrologic) for the North Brush Creek watershed which is located within the NPRB. The statistical model related snowpack (Snow Water Equivalent) from SNOTEL stations to snowmelt using the Partial Least Squares Regression technique. The hydrologic model selected was the Variable Infiltration Capacity (VIC) model at a high spatial (4 km by 4 km) and temporal (daily) resolution. The results of these two models were compared to determine the anticipated increase in streamflow due to weather modification operations.