GEOELECTRIC DETECTION OF SALINE PLUMES IN GROUND WATER AT ALKALI LAKE, NEBRASKA

Saline lakes are common in semi-arid environments and are of interest for climate evaluation and water supply in these areas. The Sand Hills of Nebraska provide a unique field laboratory for studying the ground water flow system in these lakes. Lake salinities range three orders of magnitude from fresh to brine values, while upgradient ground water is fresh. Previous work indicates that the elevated salinity results from lake evaporation. This research evaluated the efficiency of using a towed electromagnetic array to map the discharge of saline waters from saline lakes on the kilometer scale. Using two dimensional electrical resistivity surveys collected using a capacitively coupled resistivity meter, the location of saline discharge from the lakes was mapped. The results to date indicate that the instrument can detect the plumes as long as local topography does not cause a significant increase in the depth to the water table. The lakes appear to generate independent plumes of saline water and don't appear to be well connected hydraulically. Additional work will be performed using borings to confirm the geoelectrical evidence of plume location.