A steady-state finite difference model was developed to simulate ground-water flow in four regional aquifers in Michigan’s Lower Peninsula. The Glaciofluvial, Saginaw, Parma-Bayport, and Marshall aquifers were simulated as layers 1 through 4, respectively, in the model. Separately calculated vertical conductances input to the model were used to simulate the intervening Till/“Red Beds”, Saginaw, and Michigan confining units, respectively. The model domain was laterally bound by a continuous specifiedhead boundary, formed from Lakes Michigan, Huron, St. Clair, and Erie, together with the St. Clair and Detroit River connecting channels.
The model was developed to quantify regional ground-water flow in the aquifer systems using independently determined recharge estimates. The flow model showed that groundwater heads and flows in the Glaciofluvial aquifer are controlled by local stream stages and discharges, resulting in localized flow cells accounting for 95-percent of the overall model water budget. Simulation of recharge to an unspecified water table also enabled the estimation of ground-water discharge to three Great Lakes.
A computer diskette contains all MODFLOW and MODFLOWP input files, as well as digital model surfaces and several Fortran processing routines used to construct the surfaces. The diskette also provides the data used for calibration and sensitivity analysis.
