THE FARMINGTON BAY WETLANDS, DAVIS AND SALT LAKE COUNTIES UTAH - AN EVALUATION OF THREATS POSED BY GROUND-WATER DEVELOPMENT AND CLIMATE VARIABILITY

Wetlands along the shores of Great Salt Lake are some of the most important in Utah; however, our current understanding of the ground-water hydrology of these wetlands is insufficient to assess the effects of upgradient development and climate variability on the water required to maintain the wetlands. These wetlands have a long history of anthropogenic degradation and are utilized heavily for wildlife management.

I evaluated the wetlands at the southeastern end of Great Salt Lake, in the Farmington Bay area, Davis and Salt Lake Counties, Utah, to assess the threats posed by increased upgradient ground-water development and climate variability. The Farmington Bay wetlands are mixed saline and freshwater wetlands associated with Great Salt Lake and the freshwater aquifer system along the lake's east shore. The Farmington Bay wetlands are in a ground-water discharge area adjacent to Great Salt Lake, and form a dynamic system that changes both spatially and temporally because they lie within the area influenced by lake flooding. The aquifer below the wetlands consists of both lacustrine and alluvial sediments; this Tertiary-age and younger aquifer is a sedimentary system of interbedded gravel, sand, and silt that becomes progressively finer grained toward Great Salt Lake. To determine the potential impacts posed by increased ground-water development and climate variability, I used regional, three-dimensional, steady-state and transient MODFLOW models of the east shore area to simulate ground-water flow and estimate the water budgets for the wetland areas. These simulations indicate that both reduced precipitation and increased ground-water development will cause water-level declines that result in decreased flows from springs and evapotranspiration. The modeling results indicate that subsurface inflow into the wetland areas would be most affected by increased ground-water withdrawals, and that discharge from springs that feed the wetlands would be most affected by continued reduced precipitation conditions.