WATCHING WATER EVAPORATE: EXPERIMENTS AND MODELING TRACKING THE FORMATION AND BRINE EVOLUTION OF THE GREAT SALT LAKE

The Bear River, Weber River, and Jordan River make up the majority of inputs to the Great Salt Lake (GSL), together providing almost 70% of its input water. As a terminal lake, GSL contains no outputs other than evaporation, leaving the remaining water saline and highly concentrated with respect to ions entering the system through fluvial inputs. As evaporation proceeds, mineral precipitation also occurs as the water reaches saturation with respect to particular minerals.

We used PHREEQC to create an evaporation and mineral precipitation model of the fluvial inputs to GSL. This model takes inputs of major ion concentrations to form the chemistry of the input water, as well as minerals that can precipitate in the event that the water becomes oversaturated with respect to them. The model evaporates water from this initial source through many steps, allowing minerals to precipitate out of the solution once the solution reaches saturation. To test this model, we collected water from the Bear, Weber, and Jordan Rivers. After passing samples through a 0.2 um filter, we allowed them to evaporate, collecting pH and ion data daily and alkalinity data weekly. These data were compared with the model to assess the accuracy of the model predictions. If the model can accurately predict how water from GSL inputs behaves as it evaporates, it could then be used for other closed basin lakes, potentially including paleolakes for which the chemistry of fluvial inputs can be well-constrained. We will present experiment data, model predictions, and the framework of this model to explain how it could be applied to other systems.