A groundwater model to explain past lake levels at Parkers Prairie, Minnesota, USA

Abstract

The response of a lake level to a shift in climate depends on characteristics of surficial and groundwater hydrology that are unique to that lake. Determination of the past levels of several lakes, rather than just one, can help provide a more precise determination of past hydrology and climate for a given region. The levels of several closed-basin lakes in the Parkers Prairie sandplain in west-central Minnesota were lowest about 7 ka. A steady-state analytic-element groundwater model was used to quantify the effect of changing regional groundwater recharge (N) on the altitude of the water table surrounding these lakes. Because overland flow on the sandplain is limited, the surficial hydrology of the lakes can be simplified to the net quantity lake evaporation minus precipitation ( E-P) . Both N and E - P were manipulated to force the model water table to coincide with the palaeolake levels. Model results indicate that lake levels at 7 ka can be explained primarily by reducing N to about 50-60 mm yr^-1 (40-50% of the modern value), coupled with an E - P of about 100-400 mm yr^-1 (100-400% of the modem value).