Characterization of hydrogeological settings around a hypersaline sodium sulphate lake with application of electrical resistivity tomography

Understanding the input of groundwater to the evaporite deposit formation of hypersaline lakes in the Northern Great Plains is necessary to plan their sustainable exploitation. The study showed that shallow meteoric, intertill and possibly Cretaceous groundwater of low salinity all discharge into a hypersaline sodium sulphate lake. The only outflow observed from the lake was a brine plume at its margins. Based on isotope analysis the brine appears to originate from the lake. Density difference between lake brine and discharging fresh groundwater is proposed as the driving mechanism of the brine intrusion. Freshwater gradient and hydraulic conductivity of the sediments appear to control the vertical and horizontal extension of the plume. Electrical Resistivity Tomography was used to spatially position the saline plume. However, comparisons between the results of the ERT survey with the laboratory measurements indicate the ERT generally underestimates resistivity and distorts boundaries between zones of contrasting resistivity.