Numerical Simulation of Ground‐Water Interaction with Lakes Allowing for Fluctuating Lake Levels

Most numerical models of ground‐water flow incorporate lakes as constant head nodes. We developed a computer package for the widely used MODFLOW code to simulate three‐dimensional steady‐state and transient ground‐water flow with fluctuating lake levels. This package considers precipitation to and evaporation from the lake surface, stream flow, and ground‐water inflow and outflow for multiple lakes. We demonstrate the use of the package through the results of steady‐state and transient simulations for a hypothetical ground‐water flow problem involving a lake and two streams.