Modeling the Great Salt Lake

This work investigated fluctuations in the Great Salt Lake level and volume due to variability in the climate and the hydrology of the river basins that drain to the lake, as well as internal dynamics related to the lake bathymetry and salinity. The Great Salt Lake is a terminal lake whose level is determined by the balance between inflows and outflows. Inflows are from three major rivers and precipitation directly on the lake. The only outflow is evaporation. Evaporation is sensitive to lake area, which changes with lake level according to the bathymetry. Evaporation is also sensitive to salinity, which changes the lake surface saturation vapor pressure. Salinity changes with lake volume as the total salt load in the lake becomes concentrated or diluted.; This work examined the role of topography/bathymetry in the lake dynamics and the occurrence of modes in the total volume probability distribution. Bathymetry, expressed in the form of (level-area-volume) relationships, transforms the area probability density function into the volume probability density function. Modes in the area density function are suggested to represent preferred states in the climate. These area density function modes are modified as they propagate through to the volume density function.; This work also examined the impact of salinity on GSL evaporation, through the effect that it has on saturation vapor pressure, was quantified using the water activity coefficient. The reduction in saturation vapor pressure varies from 10% to 40% depending upon salinity. This reduction in saturation vapor pressure was accommodated in a modification to the Penman equation that was used to calculate Lake Evaporation based on climate inputs. Comparisons between evaporation calculations accounting for salinity and lake evaporation estimates from mass balance and lake level observations validated these salinity modifications to the Penman equation.; The overall result of this study is an improved quantitative understanding of the large scale interactions involved in the dynamics of the Great Salt Lake basin system.