“Replacing upper MODFLOW layers with an analytic element model: An alternative to grid refinement"

Large-scale MODFLOW models tend to have very large cells, particularly when using multiple layers to represent hydrostratigraphic units. These large cells limit the representation of detailed stream networks, as well as stream-well interactions. Inset models or the recently available shared node grid refinement (LGR) package may be used to apply appropriately high grid resolutions to one or more selected areas of interest. As an alternative to the inset model approach, detailed stream flow modeling (including streamwell interactions) may also be accomplished by replacing the upper MODFLOW layer(s) by the analytic element model GFLOW. While more approximate than the use of high resolution inset or LGR models, the analytic element model can provide geometric detail over a much larger area and is often easier to implement. The success of a conjunctive MODFLOW – GFLOW model, however, depends on hydrogeologic conditions.