For use in determing the rate of loss of liquid from an impoundment, the loss being through a leak in the impoundment and further making such measurements in the presence of surface losses due to evaporation, an apparatus is set forth which includes first and second open ended columns for receiving the impounded liquid therein. The first column is isolated while the second column is communicated near the bottom thereof with a passage into the impoundment so that its height will fall with the height of liquid in the impoundment. A measuring means is interposed betwen the two columns to measure differences in height. The two columns are equipped with baffles to suppress column height agitation. The measuring means comprises first and second communicated respectively with the first and second columns, said chambers being filled with first and second liquids which are not miscible, which differ in dielectric constant, and have different densities.A two liquid interface between the liquid is defined and variations in the location of the two liquid interface indicate variation in column height between the two columns.
James C. Biard;Thomas E. Owen