Using a Groundwater Model To Analyze Depletion Mapping For The Mississippi Alluvial Plain Groundwater Project
For a depletion mapping analysis, a model of an area for a specified time period is first run under a baseline condition. Simulated groundwater flows to various simulated boundary conditions are recorded, such as for streams, groundwater levels, and wells. Next, a new well is added to one model cell, the model is rerun, groundwater flows to various boundaries are again recorded, and the results are compared with the baseline condition. Results are commonly expressed as the change in the boundary flow as a percentage of the new well’s flow. Subsequently, the new well is moved from one cell to the next, and each cell is mapped. Depletion maps have been used to establish water resources management boundaries in Nebraska for more than a decade. In addition, these maps reveal characteristics of the groundwater system of an area and of the simulation representing that system. Depletion maps generated for the MAP area demonstrate where the new wells caused increased groundwater level declines (loss of storage) or decreased groundwater discharge to streams. The depletion maps also show some characteristics and details of the groundwater model inputs, such as variations in the hydraulic conductivity assigned to simulated streams.