THE INFLUENCE OF GROUNDWATER CURRENTS ON DIFFUSION-PROCESSES IN A LAKE BOTTOM - AN OLD REPORT REVIEWED

An internal report by the senior author, brought out in 1942, is presented and reviewed with the intention to show the historical developments made around 1940. The diffusion process from a clayey and saline lake bottom towards fresh supernatant water proved to be influenced by slow upward or downward groundwater currents. The deviations from the expected diffusion profiles, as observed during the period 1936-1938, could be used to find the velocities of such currents, even if they are as low as 10 mm year-1. There were areas where water from the underlying Pleistocene aquifer discharged into the lake, and elsewhere lake water infiltrated to recharge the aquifer. The conclusions of the study were in accordance with the geohydrology of the area as existed at that time. The theoretical formulation was originally not in closed form, but it is shown to be equivalent to a recent analytical solution.