Simulation of ground-water flow in aquifers along the Susquehanna River in Columbia County, Pennsylvania

A numerical model of groundwater flow was developed for a 10.3 sq mi area along the Susquehanna River in Columbia County, east central Pennsylvania. Groundwater in the model area primarily is in secondary openings in the carbonate--and clastic-rock aquifers and primary openings in the glacial-outwash aquifer that discontinuously overlies bedrock. The groundwater flow model was calibrated under average steady-state conditions for 1981. The simulated 1981 water budget indicates an average inflow rate of 7.24 cu ft/sec. Of this, 93% is recharge from precipitation and 6.6% is boundary flow. 62% of the outflow is leakage to streams, 21% to pumpage, and 17% to evapotranspiration. The model was calibrated under transient conditions for December 22, 1980 through April 21, 1982. Water level fluctuations caused by natural stresses were more successfully simulated than those caused by pumping stresses. Three 10-year, hypothetical stress periods were simulated with the calibrated, transient model. The general impact of three pumping schemes under hypothetical drought and drought-recovery conditions were simulated. (USGS)