Geochemistry of Great Salt Lake,Utah I: Hydrochemistry since 1850

The hydrochemistry of Great Salt Lake, Utah, has been defined for the historic period, 1850 through 1982, from published data combined with new observations. The water balance depends largely on river inflow, atmospheric precipitation onto the lake surface and evaporation. Input of the major solutes can best be accounted for by mixing dilute calcium-bicarbonate type river waters with NaCl-dominated hydrothermal springs.Prior to 1930, lake concentrations fluctuated inversely with lake volume in response to small climatic variations. Since then, salt precipitation and dissolution have significantly modified lake brine compositions and have led to density stratification and the formation of brine pockets of differing composition. Brine mixing has become an important component of brine evolution. We have used calculated evaporation curves with mineral precipitation and dissolution to clarify these processes.Pore fluids represent important storage for solutes. Solute profiles can be modeled by simple one-dimensional diffusion calculations. Short-term historic variations in lake composition affect shallow pore fluids in the upper 2 metres of sediment.