On evaluating density driven groundwater flow in the closed basin

The hydrogeochemical cycle in the Pilot Valley, a closed basin, is subject to climate variability over a wide range of spatial and temporal scales over long period of time. Saturated and Unsaturated Transport Model (SUTRA) is employed in the Pilot Valley to simulate subsurface and density driven groundwater flow under various climatic and geologic conditions. A Maxey-Eakin method with coupled catchment model, aridity index and incomplete beta function for groundwater recharge distribution is integrated into the SUTRA model for various simulations. A Rayleigh number is used to analyze these circulation patterns of flow under variable climate and geologic conditions. The simulation results, under different groundwater recharge rates, indicate the existence or absence of free convection flow and salt nose movement under the playa and towards hinge line. The simulation result for a historical wet period (12 ka) has a narrow salt nose extent and a historical dry period (6 ka) has a wider salt nose extent. High permeability values generate more free convective cells and low permeability values generate less or eliminate free convective cells in the flow domain. This study will help minimize damage from extreme climatic conditions which occur frequently in the study area and also help manage water resources efficiently.