1. Precipitation and the Great Salt Lake Patrick Loury and Eliana Manangòn

2. Precipitation and Lake Level of the Great Salt Lake (GSL) Precipitation accounts for approximately 30% of the input to GSL (Lall and Mann, 1995) This input has an important control on lake surface elevation (Stephens, 1990) Since 1982, about 60% of elevation increase has resulted from greater than average precipitation and less than average evaporation rates Snow is an important component of precipitation in the Great Basin, and accounts for about 85% of total precipitation input (Baskin, et al., 2002)

3. Precipitation Breakdown By Watershed* Four watersheds comprise the Great Basin: West desert Largest area, least precipitation Utah Lake One of the largest freshwater lakes in the Western U.S. Weber River Smallest area, most precipitation Bear River Contains the largest tributary contributing to GSL (Bear River) *Data from http://www.greatsaltlakeinfo.org/Background WatershedArea (mi 2 )Average Annual Precipitation (in) Minimum Recorded Precipitation (in) Maximum Recorded Precipitation (in) West Desert1896411549 Utah Lake384620961 Weber River2476261173 Bear River743721961 Total3272378

4. Historical Data* *Data from http://www.prism.oregonstate.edu Average Value: 14.98 in Standard Deviation: 3.44 in Minimum Value: 9.06 in MaximumValue: 26.64 in

5. Precipitation Trend Over Time* On a decadal scale, the average annual precipitation in SLC seems to be increasing If this trend continues, the lake surface elevation will rise in response However, the data is not certain: Weak correlation Relatively short time period for data collection Large variability in data Precipitation (in) *Data from http://www.prism.oregonstate.eduNote: For a full list of references, see handout