An electric analog model was constructed to deal with the problem of groundwater withdrawal by many centralized supply systems from the Saginaw Formation, the primary source of water for domestic and industrial use in the Lansing, Michigan area, which has resulted in a large cone of depression which is expanding rapidly. The initial design of the model utilized data presently available. In order to determine the leakage rate, a steady-state, or equilibrium analysis of the model was initiated using actual conditions, thus eliminating all time-dependent variables from the hydrologic system. The model was then modified for transient analysis until the analog simulation of the decline in the piezometric surface for several periods agreed closely with actual declines. It was also necessary to make a detailed examination of the pumpage from the aquifer. Determination of the leakage that was occurring from the glacial drift, in units of gallons per day square mill per foot of head difference was also about the hydrology of the Saginaw Formation. (WRSIC Abstract)