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In cooperation with the Delaware River Basin Commission

Estimated Ground-Water Availability in the Delaware River Basin, 1997-2000

U.S. Geological Survey Scientific Investigations Report 2006-5125--Version 1.1

By Ronald A. Sloto and Debra E. Buxton


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.

Errata sheet--5/25/07

Download the report--Version 1.1 (18.3 MB)

ABSTRACT

Ground-water availability using a watershed-based approach was estimated for the 147 watersheds that make up the Delaware River Basin. This study, conducted by the U.S. Geological Survey in cooperation with the Delaware River Basin Commission (DRBC), supports the DRBCís Water Resources Plan for the Delaware River Basin. Different procedures were used to estimate ground-water availability for the region underlain by fractured rocks in the upper part of the basin and for surficial aquifers in the region underlain by unconsolidated sediments in the lower part of the basin. The methodology is similar to that used for the Delaware River Basin Commissionís Ground-Water Protected Area in Pennsylvania. For all watersheds, ground-water availability was equated to average annual base flow.

Ground-water availability for the 109 watersheds underlain by fractured rocks in Delaware, New Jersey, New York, and Pennsylvania was based on lithology and physiographic province. Lithology was generalized by grouping 183 geologic units into 14 categories on the basis of rock type and physiographic province. Twenty-three index streamflow-gaging stations were selected to represent the 14 categories. A base-flow-recurrence analysis was used to determine the average annual 2-, 5-, 10-, 25-, and 50-year-recurrence intervals for each index station. A GIS analysis used lithology and base flow at the index stations to determine the average annual base flow for the 109 watersheds. Average annual base flow for these watersheds ranged from 0.313 to 0.915 million gallons per day per square mile for the 2-year-recurrence interval to 0.150 to 0.505 million gallons per day per square mile for the 50-year-recurrence interval.

Ground-water availability for watersheds underlain by unconsolidated surficial aquifers was based on predominant surficial geology and land use, which were determined from statistical tests to be the most significant controlling factors of base flow. Twenty-one index streamflow-gaging stations were selected to represent the 13 categories of predominant surficial geology and land use for the 38 Coastal Plain watersheds. A base-flow-recurrence analysis was used to determine the average annual 2-, 5-, 10-, 25-, and 50-year-recurrence intervals for each group of predominant surficial geology and land use. Average annual base flow for these watersheds ranged from 0.465 to 1.169 million gallons per day per square mile for the 2-year-recurrence interval to 0.178 to 0.670 million gallons per day per square mile for the 50-year-recurrence interval.

Estimated 2-, 5-, 10-, 25-, and 50-year annual base-flow-recurrence interval values for each watershed in the Delaware River Basin are considered to be the quantity of ground water available for each watershed over a range of climatic conditions. The recurrence intervals are considered to be relative indicators of climatic difference; the 2-year-recurrence value represents wetter years, and the 50-year-recurrence value represents drier years. The remaining available ground water in each watershed was determined by subtracting current (1997-2000) ground-water withdrawals and consumptive domestic use and adding water recharged by agricultural irrigation and land application of treated-sewage effluent. Ground-water use ranged from 0 to 60.8 percent of available ground water for the 2-year-recurrence interval; it exceeded 25 percent in four watersheds and 50 percent in two watersheds. Ground-water use ranged from 0 to 75.9 percent of available ground water for the 5-year-recurrence interval; it exceeded 25 percent in five watersheds and 50 percent in three watersheds. Ground-water use ranged from 0 to 84.5 percent of available ground water for the 10-year-recurrence interval; it exceeded 25 percent in seven watersheds and 50 percent in four watersheds. Ground-water use ranged from 0 to 103 percent of available ground water for the 25-year-recurrence interval; it exceeded 25 percent in nine watersheds, 50 percent in three watersheds, and 100 percent in one watershed. Ground-water use ranged from 0 to 127 percent of available ground water for the 50-year-recurrence interval; it exceeded 25 percent in 11 watersheds, 50 percent in 6 watersheds, and 125 percent in 1 watershed. If ground water pumped for quarry dewatering is not considered as a withdrawal, the ground-water use percentage in some watersheds would drop substantially.

Table of Contents

Abstract
Introduction
     Purpose and Scope
     Study Area
Ground-Water Availability
     Watershed Characteristics
          Geologic Units
          Ground-Water Withdrawals
          Ground-Water Recharge
          Domestic Water Use
          Assumptions and Limitations
     Estimation of Ground-Water Availability for Fractured Rock
          Index Stations
          Precambrian to Ordovician Crystalline Rocks of the Piedmont Physiographic Province
          Triassic Clastic Rocks and jurassic Diabase
          Precambrian and Cambrian Crystalline Rocks of the Reading Prong
          Ordovician Clastic Rocks of the Ridge and Valley Physiographic Province
          Cambrian and Ordovician Carbonate Rocks of the Ridge and Valley Physiograph Province
          Silurian Clastic Rocks
          Mississippian and Pennsylvanian Clastic Rocks
          Devonian Clastic Rocks
               Blue Mountain Section of the Ridge and Valley Physiographic Province
               Glaciated Pocono Plateau Section of the Appalachian Plateaus Physiographic Province
               Glaciated Low Plateau Section of the Appalachian Plateaus Physiographic Province
               Catskill Mountains Section of the Appalachian Plateaus Physiographic Province
               Southern New York Section of the Appalachian Plateaus Physiographic Province
          Comparison between Base Flow Estimated by Hydrograph Separation and Spatial-Data Analysis
     Estimation of Ground-Water Availability for Unconsolidated Sediments
     Index Stations
     Predominant Surficial Geology and Land-Use Categories in New Jersey Coastal Plain Watersheds
          Salt Marsh and Estuarine Deposits and Undeveloped Land Use
          Lower and Upper Stream-Terrace Deposits and Undeveloped Land Use
          Cape May Formation
               Undeveloped Land Use
               Agricultural Land Use
          Weathered Coastal Plain Formations
               Urban Land Use
               Undeveloped Land Use
               Agricultural Land Use
          Bridgeton Formation
               Urban Land Use
               Undeveloped Land Use
               Agricultural Land Use
     Predominant Land-Use Categories in the Delaware Coastal Plain Watersheds
          Urban Land Use
          Undeveloped Land Use
          Agricultural Land Use
     Ground-Water Availability and Use by Watershed in the Delaware River Basin
Summary
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.

Download the report--Version 1.1 (18.3 MB)

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