Aquifer model of the Susquehanna River valley in southwestern Broome County, New York

Water-Resources Investigations Report 85-4099




A finite-difference model of groundwater flow within stratified drift in the 14 mi reach of the Susquehanna River valley from Binghamton west to 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, the lower layer generally represents older ice-contact deposits; and 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. The model was calibrated for average steady-state conditions from data for April 1981, when water levels remained fairly stable for nearly 2 months. Recharge from precipitation on the aquifer during this period was determined to be about 1.28 in/mo. Transmissivity of the lower aquifer, as determined by calibration of the model for areas influenced by pumping, was significantly less than transmissivity values calculated from pumping records or geologic logs of individual wells. This difference is attributed to scattered silty layers that reduce average transmissivity of generally permeable materials. Data are available for transient calibration, including: (1) semiannual water level measurements that reflect seasonal changes in river stage, pumping, and recharge; (2) short-term pumping tests at several sites; and (3) measurements in the Clinton Street-Ballpark aquifer before 1967, when pumpage was 30 % greater than in 1981. Transient calibration would improve the accuracy and predictive capability of the model. (Lantz-PTT)

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Aquifer model of the Susquehanna River valley in southwestern Broome County, New York
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Water-Resources Investigations Report
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U.S. Geological Survey,
vi, 38 p. :ill., maps ;28 cm.