Abstract
Great Salt Lake of Utah is among the largest and most ecologically important water bodies in North America. Since the late 1950s, the lake has been divided into two hydrologically distinct water bodies by a rock-fill railroad causeway. Flux through the causeway is driven by two forces: differential surface elevation and differential density between the north and south arms. The south arm features episodic vertical stratification due to the influx of deep, dense brine from the north arm. The source of this brine (a breach, two culverts, or subsurface flow) has been investigated over the past 50 years. Quantification of subsurface water flux through the causeway has been problematic due to the heterogeneous and slowly compacting nature of the causeway fill over time. Between 2008 and 2015, enhanced gauging of various surface inflows and outflows and density measurements made throughout the lake permitted detailed water volume calculations of both lake arms. Results show that during high precipitation years, density-driven, north-to-south flow through the causeway predominates due to freshening of water in the south arm. At other times, south-to-north head gradient driven flow and north-to-south density-driven flow are approximately equal. The model suggests subsurface flux through the causeway is one important driver of the ecologically important deep brine layer in the south arm of the lake over the past 20 years.
Highlights
Saline lakes have long been recognized for their cultural and scientific importance
South arm mass balances consist of river inflows, precipitation minus evaporation, and net flux through the causeway breach, culverts, and subsurface flow through the rock-fill causeway
Kca is net subsurface flux through the causeway; Kgw is groundwater flow; KeT is total evaporation as calculated in Eq (1); and z is the fraction of evaporation in the north arm divided by total lake evaporation (Table 1)
Summary
A common feature of these lakes is distinctive water masses separated by sharp vertical density gradients. Examples of human-caused stratification include Big Soda Lake in the western Great Basin of the U.S [19, 38], Salton Sea [20] and Mono Lake [15] in California, and the southern arm of Great Salt Lake of the eastern Great Basin [13]. Vertical stratification often leads to anoxic bottom waters with anomalously high metal concentrations Understanding the controls by which these water masses form and disappear is a critical question in the field of physical limnology and lacustrine geochemical cycles
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