WHAT MAKES THE GREAT SALT LAKE LEVEL GO UP AND DOWN?

The Great Salt Lake (GSL), Utah, is the fourth largest, perennial, terminal lake in the world. Fluctuations of the GSL's level are of direct concern because high levels threaten infrastructures, while low levels put large scale industries in jeopardy. Inflows are due to streamflow, primarily from the Bear River (54%), Weber River (18%) and Jordan/Provo River (28%) systems. Inflows also include precipitation directly on the lake and groundwater both from the East and West sides. The only outflow is evaporation that is controlled by the climate and area of the lake that changes with level. The GSL reached historic high levels above 1284 m in 1873 and 1986. A historic low at 1278 m occurred in 1963. These fluctuations represent the dynamic interactions between the climate and hydrology of the Great Salt Lake Basin as well as the dynamic interaction between lake volume, area and salinity that impact evaporation from the lake. This paper examines the relationships between Basin climate (precipitation and temperature), Inflows to the lake (primarily streamflow) and outflows (evaporation). Historic streamflow used is from USGS stations, both unimpacted hydroclimatic stations and major inflows to the lake near the downstream end of rivers. Forcing data of precipitation and other climate indices will be the University of Washington (1/8) degree gridded meteorological data that provides basinwide climate inputs. We separate lake volume changes into increases in the spring (due to spring runoff) and declines in the fall (due to evaporation). These are then analyzed and related to precipitation, streamflow and climate. Consideration of potential climate change in the intermountain West has produced scenarios for trends of increases in precipitation and decreases in snowpack. Due to that we would like to use our analysis to assess the implications of climate variability on the future level of the lake. This analysis would contribute to better understand how both external forcings and internal feedbacks are involved in GSL basin system dynamics.