Comparison of numerical methods in simulating lake–groundwater interactions: Lake Hampen, Western Denmark

The numerical simulation of lake–groundwater interaction dynamics is very challenging, and, thus, only few model codes are available. The present study investigated the performance of a new method, namely, the Sloping Lakebed Method (SLM), in comparison to the widely used MODFLOW lake package (LAK3). Coupled lake–groundwater models based on LAK3 and SLM were developed for Lake Hampen, Denmark. The results showed that both methods had essentially the same accuracy when simulating the lake water level, the groundwater head and the overall water balance. The SLM-based model had the potential to reproduce the change of the lake surface area in a more natural way. Moreover, the vertical discretization of a lake in the SLM is independent of the groundwater model, and, thus, the model grid at the top layers could be considerably coarsened without a loss of model accuracy. This could lead to savings in computational time of approximately 30%.