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

Abstract

A numerical model of ground-water flow was developed for a 10.3-squaremile area along the Susquehanna River in Columbia County, east-central Pennsylvania. Ground water in the model area primarily is in secondary openings in the carbonateand clastic-rock aquifers and primary openings in the glacial-outwash aquifer that discontinuously overlies bedrock. The ground-water flow model was calibrated under average steady-state conditions for 1981. The simulated 1981 water budget indicates an average inflow rate of 7.24 cubic feet per second. Of this, 93 percent is recharge from precipitation and 6.6 percent is boundary flow. Sixty-two percent of the outflow is leakage to streams, 21 percent to pumpage, and 17 percent 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. INTRODUCTION A project was done by the U.S. Geological Survey in cooperation with the Susquehanna River Basin Commission as part of their Special Ground-Water Study funded through the U.S. Water Resources Council. The objective of the Special Ground-Water Study is to determine the availability, distribution, and quality of the ground-water resources in the Susquehanna River basin. The objectives of the study addressed In this report are to: 1. Conceptualize and quantify ground-water flow in a complex aquifer system; and 2. Provide a means of evaluating the general impact of potential stresses on the aquifer system. The area along the Susquehanna River between Berwick and Bloomsburg in Columbia County was selected for a modeling study because: (1) it is underlain by a carbonate-rock aquifer of regional importance as a present and potential source of water for municipal, commercial, and industrial use; (2) significant amounts of ground water are presently withdrawn in the area and additional ground-water development is predicted; and (3) data collected as part of an investigation of the ground-water resources of Columbia County and surrounding 1 area by Williams and Eckhardt (1987) could be used in model development. This report discusses the development and use of a numerical model of ground-water flow in bedrock and glacial-outwash aquifers along the Susquehanna River in Columbia County, Pennsylvania. Location and Physiographic Setting The study area is located along the Susquehanna River between Berwick and Bloorasburg in Columbia County, east-central Pennsylvania (fig. 1). A 10.3 mi (square mile) area was modeled. The area is within the Appalachian Mountain Section of the Valley and Ridge Physiographic Province. The Appalachian Mountain Section is characterized by mountainous terrain consisting of a series of long valleys and narrow ridges. The model area is characterized by flat terraces and steep slopes. The terrace area averages about 3,000 ft (feet) wide and ranges in altitude from 450 to 500 ft above sea level. A sharp topographic break is present between the terrace and slope areas. The slope area generally is 1,000 to 2,000 ft wide and its altitudes are as high as 700 ft above sea level. The model area is drained by the Susquehanna River, Fishing Creek, and four smaller streams (fig. 1). Population centers include Bloomsburg, Espy, Almedia, and Lime Ridge. / > --_ Farms Well Field LIME RIDGEr* COLUMBIA COUNTY BERWICK BLOOMSBURG KILOMETER