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Pennsylvania Water Science Center

Estimates of Ground-Water Recharge Based on Streamflow-Hydrograph Methods: Pennsylvania

U.S. Geological Survey Open-File Report 2005-1333

By Dennis W. Risser, Randall W. Conger, James E. Ulrich, and Michael P. Asmussen

This report is available as a pdf.


This study, completed by the U.S. Geological Survey (USGS) in cooperation with the Pennsylvania Department of Conservation and Natural Resources, Bureau of Topographic and Geologic Survey (T&GS), provides estimates of ground-water recharge for watersheds throughout Pennsylvania computed by use of two automated streamflow-hydrograph-analysis methods--PART and RORA. The PART computer program uses a hydrograph-separation technique to divide the streamflow hydrograph into components of direct runoff and base flow. Base flow can be a useful approximation of recharge if losses and interbasin transfers of ground water are minimal. The RORA computer program uses a recession-curve displacement technique to estimate ground-water recharge from each storm period indicated on the streamflow hydrograph.

Recharge estimates were made using streamflow records collected during 1885-2001 from 197 active and inactive streamflow-gaging stations in Pennsylvania where streamflow is relatively unaffected by regulation. Estimates of mean-annual recharge in Pennsylvania computed by the use of PART ranged from 5.8 to 26.6 inches; estimates from RORA ranged from 7.7 to 29.3 inches. Estimates from the RORA program were about 2 inches greater than those derived from the PART program.

Mean-monthly recharge was computed from the RORA program and was reported as a percentage of mean-annual recharge. On the basis of this analysis, the major ground-water recharge period in Pennsylvania typically is November through May; the greatest monthly recharge typically occurs in March.

Table of Contents

Streamflow-Hydrograph Methods
     Hydrograph Separation - PART Program
     Recession-Curve Displacement - RORA Program
Ground-Water Recharge Estimates
     Selection of Streamflow-Gaging Stations
     Mean-Annual Recharge
     Mean-Monthly Recharge
References Cited

For more information about USGS activities in Pennsylvania contact:
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:

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