Applications of MODFLOW with a lake package to simulate ground water/lake interaction.
A new computer package to simulate water-level fluctuations in lakes was developed and incorporated into the U. S. Geological Survey’s modular three-dimensional finite-difference ground-water flow model (MOD FLOW). We demonstrate the use of the new package with applications to the National Science Foundation’s Long-Term Ecological Research (LTER) site in northern Wisconsin. The new lake package is an effective tool to study ground-water and lake interaction because it allows prediction of lake levels in addition to ground-water levels. The lake package simulates surface water bodies, such as lakes or ponds that have no surface inflows or outflows. It computes seepage into and/ or out of a lake by using lakebed sediment conductance and the head gradient between the lake and aquifer. The lake package predicts lake level by means of a mass balance calculation that includes ground-water inflow and outflow, precipitation and evaporation. A steady state model using MODFLOW with the lake package was used to simulate ground-water flow near Little Rock Lake and Sparkling Lake, two of a suite of LTER lakes, situated in Vilas County, Wisconsin. The calibrated model was applied to a scenario assuming a 10\% decrease in precipitation and ground-water recharge and a 5\% increase in lake surface evaporation in order to study the effects of potential global climate change. Results show that the simulated changes have a significant effect on the water budget of Little Rock Lake.
National Ground Water Association