MULTI-TRACER APPROACH TO CHARACTERIZING THE CHEMICAL EVOLUTION OF SPRINGWATER IN BLUE LAKE, UTAH

Aridland springs are important for both anthropogenic use and ecosystem processes, especially considering water rights issues across geopolitical borders, such as at the Utah-Nevada-Goshute Reservation border. Here, recharge in eastern Nevada flows to the NE eventually discharging to the Bonneville Basin (BB). Effective management must consider the flowpath and residence time of discharging water. Previous work has shown that recharge in the Snake Range flows ~125 km to the NE and discharges at the southern end of the BB in the Fish Springs (FS) complex with transit times up to 32 kyr. Here we investigate analogous systems to the east of the Deep Creek and Goshute Ranges which may flow to a regional discharge point at Blue Lake, UT (BL). In both cases, complex inter-basin flowpaths through regional carbonate and volcanic aquifers are required to feed springs that discharge at the margins of BB where regional flow paths encounter marl, gypsum, and halite deposits. Where these two sets hydrostratigraphic units are in contact warm springs exist and support important ecological functions, in addition to a long history of human occupation and use. BL was sampled bi-monthly beginning in 2016 and analyzed for major cations and anions in addition to stable isotopic composition to evaluate possible links to meteoric patterns. The physical and chemical similarities between FS and BL support a regionally relevant conceptual model; however, BL has higher solute concentrations, notably Na+ and Cl-, as well as Sr isotopic composition (87Sr/86Sr =0.7135) that indicate dissolution of BB deposits. Preliminary results of these samples yield 10.1 percent modern carbon from 14C analysis of dissolved inorganic carbon, yielding an uncorrected age of ~16 ka. If this water was recharged during the Last Glacial Maximum, dissolved N2/Ar ratios yield curiously high recharge temperatures (19–22°C). Anthropogenic environmental tracers (CFCs, SF6, 3H) document a component of young water in the mixture and highlight the potential for environmental pollutants to contaminate the aquifer in spite of its regional extent and long residence time. In addition to addressing water rights, these results also provide constraints on the water and solute budgets of the Bonneville Salt Flats which support a wide array of economic and recreational activity.