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Publications— Open-File Reports |
In cooperation with the Pennsylvania Department of Environmental Protection
U.S. Geological Survey Open-File Report 2006-1143
By Dennis W. Risser
This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.
View the full report in PDF 5.5 MB
This report, prepared in cooperation with the Department of Environmental Protection, Office of Mineral Resources Management, provides a preliminary analysis of water budgets
and generalized ground-water/surface-water interactions for Bushkill and parts of Monocacy Creek watersheds in Northampton County, Pa., by use of a ground-water flow model.
Bushkill Creek watershed was selected for study because it has areas of rapid growth, ground-water withdrawals from a quarry, and proposed stream-channel modifications,
all of which have the potential for altering ground-water budgets and the interaction between ground water and streams.
Preliminary 2-dimensional, steady-state simulations of ground-water flow by the use of MODFLOW are presented to show the status of work through September 2005 and help guide
ongoing data collection in Bushkill Creek watershed. Simulations were conducted for (1) predevelopment conditions, (2) a water table lowered for quarry operations, and
(3) anthropogenic changes in hydraulic conductivity of the streambed and aquifer. Preliminary results indicated under predevelopment conditions, the divide between the
Bushkill and Monocacy Creek ground-water basins may not have been coincident with the topographic divide and as much as 14 percent of the ground-water discharge to Bushkill
Creek may have originated from recharge in the Monocacy Creek watershed. For simulated predevelopment conditions, Schoeneck Creek and parts of Monocacy Creek were dry,
but Bushkill Creek was gaining throughout all reaches.
Simulated lowering of the deepest quarry sump to an altitude of 147 feet for quarry operations caused ground-water recharge and streamflow leakage to be diverted to the
quarry throughout about 14 square miles and caused reaches of Bushkill and Little Bushkill Creeks to change from gaining to losing streams. Lowering the deepest quarry
sump to an altitude of 100 feet caused simulated ground-water discharge to the quarry to increase about 4 cubic feet per second. Raising the deepest sump to an altitude
of 200 feet caused the simulated discharge to the quarry to decrease about 14 cubic feet per second.Decreasing the hydraulic conductivity of the streambed of Bushkill
Creek in the reach of large losses of flow caused simulated ground-water levels to decline and ground-water discharge to a quarry to decrease from 74 to 45 cubic feet per second.
Decreasing the hydraulic conductivity of a hypothesized highly transmissive zone with a plug of relatively impermeable
material caused ground-water levels to increase east of the plug and decline west of the plug, and decreased the discharge to a
quarry from 74 to 53 cubic feet per second. Preliminary results of the study have significant limitations,
which need to be recognized by the user. The results demonstrated the usefulness of ground-water modeling with available
data sets, but as more data become available through field studies, a more complete evaluation could be conducted of the
preliminary assumptions in the conceptual model, model sensitivity, and effects of boundary conditions. Additional streamflow and ground-water-level measurements would be needed to
better quantify recharge and aquifer properties, particularly the anisotropy of carbonate rocks. Measurements of streamflow losses at average, steady-state hydrologic conditions could provide
a more accurate estimate of ground-water recharge from this source, which directly affects water budgets and contributing areas simulated by the model.
Abstract
Introduction
Purpose and Scope
Previous Investigations
Hydrogeologic Setting
Available Data
Water-Level Measurements
Discharge Measurements
Simulated Water Budgets and Ground-Water/Surface-Water Interactions
Conceptual Model
Model Development
Computer Code and Grid
Boundary Conditions
Recharge from Precipitation
Streams
Quarry
Wells
Aquifer Properties
Model Adjustments
Weighting of Measurements
Adjusted Model Parameters
Preliminary Results of Model Simulations
Predevelopment Conditions
Effects of a Water Table Lowered for Quarry Operations
Effects of Changes in Hydraulic Conductivity
Streambed Hydraulic Conductivity
Highly Transmissive Zone
Horizontal Anisotropy Ratio
Assumptions and Limitations of the Preliminary Model
Suggestions for Future Data Collection
Summary
References Cited
This report is available online in Portable Document Format (PDF). If you do not have the Adobe Acrobat PDF Reader, it is available for free download from Adobe Systems Incorporated.
View the full report in PDF 5.5 MB
For more information about USGS activities in Pennsylvania contact:
Director
USGS Pennsylvania Water Science Center
215 Limekiln Road
New Cumberland, Pennsylvania 17070
Telephone: (717) 730-6960
Fax: (717) 730-6997
or access the USGS Water Resources of Pennsylvania home page at:
http://pa.water.usgs.gov/.
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