A Mass Balance Model of the Great Salt Lake, UT With Adaptive Management Applications

The Great Salt, Utah, USA is a saline lake that provides critical habitat for ecologic communities and generates $1.3 billion annually. It has gone through detrimental change since the 20th century. Streamflow reaching the lake has been decreased by upstream withdrawal for industrial and municipal use, causing the lake level to drop and salinity to increase to unhealthy levels. Further, in 1959, it was segregated into north and south sections by a railroad causeway. Due to the causeway and limited exchange of water through two bridges, the lake sections have significantly different water surface elevation and salinity levels. The most recent bridge in the causeway, known as the New Breach, was constructed with a rock berm that is raised or lowered to control exchange of water between the sections and can be used to maintain healthy salinity levels. Lake managers have utilized the New Breach berm to adaptively manage salinity; raising it 1.2 m in 2022 and another 1.5 m in 2023 in response to record low lake level and high salt concentrations in the south section. To inform future adaptive management decisions such as these, this research developed a model that can predict salinity and water level of both sections in response to various inflow, climate, and berm height conditions. Results from application of the model showed that the New Breach berm is a helpful tool, but long-term salinity management of the Great Salt Lake will require increasing streamflow to the lake. Additional analysis of data gathered for use in developing the model highlighted data limitations and how monitoring of the Great Salt Lake can be improved in the future to better aid decision making