HOT SPRINGS IN THE WATERSHED OF UTAH LAKE, CENTRAL UTAH: AN ESSENTIAL COMPONENT OF A HYDROLOGIC MODEL FOR UTAH LAKE

By surface area, Utah Lake is the third largest natural freshwater lake in the western United States. There are existing hydrologic models for Utah Lake, but they do not include hot springs as a component. Since hot springs are abundant within, on the shores of, and within the watershed of Utah Lake, the objective of this study has been to develop a model for the origin of hot springs as a step towards a more comprehensive hydrologic model for Utah Lake. The objective was addressed by collecting samples from 12 cold, warm and hot springs, as well as eight streams upstream and downstream of the springs, in the vicinity of Diamond Fork canyon, about 18 and 30 kilometers southeast of the base of the Wasatch Mountains and Utah Lake, respectively. Measurements included temperature, pH, electrical conductivity, dissolved oxygen, redox potential, and stable isotopes of hydrogen and oxygen. Measurements of metals and CFC concentrations are still in progress. Over a distance of about three kilometers, spring parameters varied widely, ranging from 14.5 to 52.4 °C, 6.76 to 7.95, 1176 to 11,640 μS/cm, 0.64 to 6.85 mg/L, and -8.0 to 194.5 mV for temperature, pH, electrical conductivity, dissolved oxygen, and redox potential, respectively. A strong negative correlation (R² = 0.97) between spring temperature and deuterium composition δ²H implies that warmer springs are recharged through the longer and deeper flow paths originating at higher elevations. In the same way, a strong negative correlation (R² = 0.65) between spring pH and δ²H implies that more alkaline springs are recharged at higher elevations with longer passage through the Paleocene-Eocene Flagstaff Limestone. Nearly all stable isotopic compositions fell along the known Local Meteoric Water Line (LMWL) for Utah Lake, indicating recharge by precipitation without significant evaporation or isotopic fractionation along groundwater pathways. The only exceptions were three samples from Sixth Water Creek (both upstream and downstream of hot springs), which is fed by Strawberry Reservoir through Strawberry Tunnel. These samples fell along the known Local Evaporation Line (LEL) for Utah Lake, contradicting previous work that concluded that significant evaporation did not occur in the reservoirs and lakes in the Utah Lake watershed. Further results will be reported at the meeting.