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Pennsylvania Water Science Center

U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2005-5113

Water Budgets for Selected Watersheds in the Delaware River Basin, Eastern Pennsylvania and Western New Jersey

By: Ronald A. Sloto and Debra E. Buxton

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ABSTRACT

This pilot study, done by the U.S. Geological Survey in cooperation with the Delaware River Basin Commission, developed annual water budgets using available data for five watersheds in the Delaware River Basin with different degrees of urbanization and different geological settings. A basin water budget and a water-use budget were developed for each watershed. The basin water budget describes inputs to the watershed (precipitation and imported water), outputs of water from the watershed (streamflow, exported water, leakage, consumed water, and evapotranspiration), and changes in ground-water and surface-water storage. The water-use budget describes water withdrawals in the watershed (ground-water and surface-water withdrawals), discharges of water in the watershed (discharge to surface water and ground water), and movement of water of water into and out of the watershed (imports, exports, and consumed water). The water-budget equations developed for this study can be applied to any watershed in the Delaware River Basin. Data used to develop the water budgets were obtained from available long-term meteorological and hydrological data-collection stations and from water-use data collected by regulatory agencies. In the Coastal Plain watersheds, net ground-water loss from unconfined to confined aquifers was determined by using ground-water-flow-model simulations. Error in the water-budget terms is caused by missing data, poor or incomplete measurements, overestimated or underestimated quantities, measurement or reporting errors, and the use of point measurements, such as precipitation and water levels, to estimate an areal quantity, particularly if the watershed is hydrologically or geologically complex or the data-collection station is outside the watershed. The complexity of the water budgets increases with increasing watershed urbanization and interbasin transfer of water. In the Wissahickon Creek watershed, for example, some ground water is discharged to streams in the watershed, some is exported as wastewater, and some is exported for public supply. In addition, ground water withdrawn outside the watershed is imported for public supply or imported as wastewater for treatment and discharge in the watershed. A GIS analysis was necessary to quantify many of the water-budget components.

The 89.9-square mile East Branch Brandywine Creek watershed in Pennsylvania is a rural watershed with reservoir storage that is underlain by fractured rock. Water budgets were developed for 1977-2001. Average annual precipitation, streamflow, and evapotranspiration were 46.89, 21.58, and 25.88 inches, respectively. Some water was imported (average of 0.68 inches) into the watershed for public-water supply and as wastewater for treatment and discharge; these imports resulted in a net gain of water to the watershed. More water was discharged to East Branch Brandywine Creek than was withdrawn from it; the net discharge resulted in an increase in streamflow. Most ground water was withdrawn (average of 0.25 inches) for public-water supply. Surface water was withdrawn (average of 0.58 inches) for public-water and industrial supply. Discharge of water by sewage-treatment plants and industries (average of 1.22 inches) and regulation by Marsh Creek Reservoir caused base flow to appear an average of 7.2 percent higher than it would have been without these additional sources. On average, 67 percent of the difference was caused by sewage-treatment-plant and industrial discharges, and 33 percent was caused by regulation of the Marsh Creek Reservoir. Water imports, withdrawals, and discharges have been increasing as the watershed becomes increasingly urbanized.

The 64-square mile Wissahickon Creek watershed in Pennsylvania is an urban watershed underlain by fractured rock. Water budgets were developed for 1987-98. Average annual precipitation, streamflow, and evapotranspiration were 47.23, 22.24, and 23.12 inches, respectively. The watershed is highly urbanized, and there is a complex system of interbasin water transfers. Water was imported into the basin for public-water supply and as wastewater for treatment and discharge. Ground water was exported from the watershed for public-water supply. Because more water was exported (average of 1.78 inches) than imported (average of 1.64 inches), there was a net loss of water from the watershed. Most ground-water withdrawals (average 3.03 inches) were for public and industrial supply, whereas most surface-water withdrawals (average of 0.09 inches) were for golf course irrigation. A quarry in the watershed pumped a substantial quantity of ground water (average of 2.9 inches) for quarry dewatering. Water pumped for dewatering the quarry was equal, on average, to 49 percent of all ground-water withdrawals in the watershed. This water. discharged to the creek, constituted an average of 25 percent of the base flow of Wissahickon Creek. Discharge of water by sewage-treatment plants, industries, and the quarry (average total of 5.3 inches) caused base flow in the creek to appear higher than it would have been without these additional sources and constituted an average of about 44 percent of the observed base flow. Water imports, exports, withdrawals, and discharges have been steady over time.

The 46.5-square mile Pocono Creek watershed in Pennsylvania is a rural watershed underlain by fractured rock. Water budgets were developed for 1975-2001. Average annual precipitation, streamflow, and evapotranspiration were 49.70, 22.08, and 27.43 inches, respectively. Some water was exported from the watershed (average of 0.18 inches) for public-water supply. Most of the residents of the watershed relied on domestic wells and septic systems. Most of the nondomestic ground-water withdrawals (average of 0.52 inches) and all of the surface-water withdrawals (average of 0.09 inches) and discharges (average of 0.07 inches) were by a ski resort. Water exports, withdrawals, and discharges have been increasing over time because of the growth of the ski industry and population growth in the Pocono Creek and surrounding watersheds.

The 77.9-square mile Greenwood Branch of the Rancocas Creek watershed in New Jersey is a rural watershed in the Coastal Plain dominated by forest and wetlands. Water budgets were developed for 1988-2002. Average annual precipitation, streamflow, and evapotranspiration were 44.73, 18.25, and 23.43 inches, respectively. Many private residences relied on domestic wells and septic systems. Most of the water supply, including that from half the domestic wells, came from confined aquifers. The majority of ground-water withdrawals (average of 0.44 inches) were for public supply and quarry dewatering (average of 1.14 inches). Water pumped for dewatering a sand quarry was equal, on average, to 72 percent of ground-water withdrawals in the watershed. Most surface-water withdrawals (average of 0.62 inches) were for public and agricultural supply. The main type of agriculture is cranberry production. Surface water was exported (average of 0.3 inches) for use at the Fort Dix Army Base, which is north of the watershed. Most consumptive use was for cranberry production and sand mining (average 0.14 inches). Ground-water returns (average of 1.42 inches) were dominated by the water used in cranberry production and quarry dewatering. Surface-water discharge (average of 0.31 inches) was mainly from cranberry production.

The 51.3-square mile Cooper River watershed in New Jersey is a mostly urban watershed in the Coastal Plain with an intricate system of water use. The southeastern part of the watershed is rural and was mainly self-supplied. Water budgets were developed for 1988-2002. Average annual precipitation, streamflow, and evapotranspiration were 44.11, 22.13, and 24.13 inches, respectively. Most of the water that was withdrawn and exported from the basin came from confined aquifers. The small amount of water withdrawn from unconfined aquifers (average of less than 0.01 inches) and surface-water sources (average 0.77 inches) was used for golf-course, agricultural, and nonagricultural irrigation and some industrial purposes. A regional sewer system completed in 1991 dramatically reduced discharge to surface water in the watershed from 2.95 inches in 1988 to 0.01 inches in 1994.

Table of Contents

Abstract                              
Introduction                                                        
     Purpose and scope
     Description of selected watersheds
Methods of calculating water budgets
     Basin water-budget calculations
     Water-use budget calculations
     Sources of data
     Limitations and sources of error
Water budgets for individual watersheds
     Fractured-rock-aquifer watersheds
          East Branch Brandywine Creek watershed
          Wissahickon Creek watershed
          Pocono Creek watershed
     Coastal Plain-aquifer watersheds
          Greenwood Branch of the Rancocas Creek watershed
          Cooper River watershed
Comparison of water budgets
Summary and conclusions
Acknowledgments
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 2044 KB

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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