An Examination of External Influences Embedded in the Historical Snow Course Data of Utah

Snowpack data collection has a long and storied history in Utah as well as the western United States. In Utah, records extend back to at least 1912. Systematic measurements began in the mid 1920's with many long-term snow courses established at that time. Each site was meticulously mapped, described and most important, photographed from several angles. Comparisons are made between the 1936 photographs, maps and descriptions and current conditions, specifically with regard to vegetation. General conclusions are made regarding the impact that vegetation change has had on snow accumulation at each course. With the advent of weather modification programs, changes in snow accumulation could reasonably be expected. Utah began a relatively small test weather modification program in the 1950's in central Utah. The Utah cloud seeding act was passed in 1973 and the seeding program has continued since that time. Snow Courses affected by this program are identified and the potential impact on historical data. The impact of sensor change from steel pillows to hypalon is discussed. Physical changes at data collection sites are estimated. Finally, recommendations for individual snow course suitability for long-term study based on consistency are made for each of the courses examined. SNOTEL sites, the automated version of the snow courses began to be installed in the late 1970's and early 1980's. These sites to a lesser degree due to the shorter historical time of data collection, have been impacted by vegetation change as well.