A finite-difference model of ground-water flow within stratified drift in the 14-mile reach of the Susquehanna River valley from Binghamton west to the Tioga County line (including Johnson City, Endicott, and Vestal) has been developed. Outwash is the most permeable and extensive type of stratified drift in the valley but has only small saturated thickness except where it is downwarped beneath ice-block depressions. The outwash is commonly underlain by extensive beds of silt and clay deposited in proglacial lakes. Older ice-contact deposits are also extensive and provide the largest yields to wells but are highly variable in thickness and commonly siltier than the outwash. The ice-contact deposits seem to occur mainly as ridges that parallel the axis of major valleys and are buried beneath later lacustrine and outwash sediments.
The model simulates horizontal flow in two layers; the upper layer generally represents outwash, and the lower layer generally represents older ice-contact deposits. The model also simulates vertical flow between those layers through the beds of silt and clay or, where the two aquifer layers are in direct contact, through sand and gravel.
The model has been calibrated to reproduce observed water levels that represent steady-state conditions. Aquifer properties, recharge from several sources, river stage, and pumpage from several municipal and industrial well fields were calculated from data collected largely in 1981. Major streams were treated as constant specified heads in the upper layer. Data are available to refine the calibration.
