Wetlands in northern Salt Lake Valley, Salt Lake County, Utah

4Utah Geological SurveyFigure 3. Annual water usages by category for Salt Lake Valley (based on data from Utah Division of Water Rights).Purpose and ScopeThe purpose of this study is to use existing data to estimate awater budget for the wetland areas, and to use existing steadystateand transient ground-water flow models developed by theU.S. Geological Survey (USGS) (Lambert, 1995a) to simulatethe hydrologic effects on wetlands from various recharge ratesand projected ground-water withdrawals at various projectedGreat Salt Lake levels; the estimated water budget and modelsimulations focus on wetlands around the margins of GreatSalt Lake, although the study results may apply to all of thewetlands in Salt Lake Valley. These simulations can be usedto assess potential threats to wetlands from increased groundwaterwithdrawals and drought, and provide a basis for (1)implementing restrictions on domestic withdrawals, (2) assessingwater needs for wetland preservation, and (3) encouragingthe development of water conservation programs.Our study combines empirical and modeling analyses to understandthe effects of changes in land use and climate. Weused an estimated water budget to compare and interpretnumerical ground-water flow models, which simulate fluxesinto and out of the Salt Lake Valley wetland areas. Numericalground-water flow models have been used to understandthe interaction between wetlands and ground water in otherstudies (Burk and others, 2005; Bishop and others, 2009). Theaccuracy of the solutions obtained by numerical methods isgenerally sufficient; however, the accuracy depends on severalfactors, including our understanding of the complexityof the system, boundary and initial conditions, and numericalmethods used.A second objective is to document the hydraulic gradient andcurrent quality of ground water in the wetland areas near GreatSalt Lake. We used water levels in shallow wells to documentthe hydraulic gradient in the shallow unconfined aquifer, anddata from water samples from two of the wells to provide insightinto the current quality of ground water flowing into thewetland areas. Data from two wells are not sufficient to accuratelycharacterize the quality of ground water entering thewetland areas, but information from these two wells in additionto data from previous work provide a sense of the qualityof ground water recharging the wetland areas.This report provides the necessary integration of geologicand hydrologic wetland studies to more fully understand thehydrologic system of the Salt Lake Valley wetlands area inrelation to wetland functionality, with emphasis on the wetlandsnear Great Salt Lake. The scope of this study includes athorough literature search; a compilation of published and unpublishedgeologic, hydrologic, and wetland information; andfield sampling and analysis of water data from shallow wells.Detailed USGS ground-water models, which are describedin this report, were used by the USGS and other agencies toidentify historical changes in the ground-water flow system inSalt Lake Valley.