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Ground-water resource assessment of the Montauk area, Long Island, New York

Water-Resources Investigations Report 85-4013

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Abstract

The water resources of the Montauk area were investigated from October 1980 through September 1983 to assess the availability of fresh groundwater. The principal aquifer, which consists of fine- to coarse-grained stratified glacial drift, is the sole source of freshwater. The freshwater/saltwater interface lies as much as 150 ft below sea level, but the till unit and the marine-clay unit limit the thickness of the zone from which freshwater may easily be withdrawn to < 100 ft in most places. Precipitation, the sole source of freshwater in the Montauk area , averages about 42 in/yr. Direct runoff is approximately 1 in/yr, and evapotranspiration about 20 in/yr; the remaining 21 inches is the net recharge to the principal aquifer. The horizontal hydraulic conductivity, as calculated from specific-capacity data, ranges from 130 to 350 ft/d. Analysis of an aquifer pumping test indicates that horizontal hydraulic conductivity of the principal aquifer is approximately 275 ft/d and the vertical hydraulic conductivity is approximately 90 ft/d; the storage coefficient ranges from 1.1 x .001 to 2.2 x .001. A numerical two-dimensional flow model that simulates the areal flow of fresh- and saltwater was developed to evaluate the effects of the present level of groundwater development and the potential effects of increased future withdrawals. Model results indicate that the principal aquifer is capable of producing several times more than the 0.6 mil gal/d now being withdrawn for public supply. Examination of well design and pumping rates, and analysis of analog-model studies of saltwater upconing to wells, indicate that the peak pumping rate of public supply wells exceeds the limit necessary to avoid contamination from saltwater. With proper well design and distribution of pumping stress, the aquifer system would be capable of supplying enough water to meet the needs of the population projected through 1995. (Author 's abstract)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Ground-water resource assessment of the Montauk area, Long Island, New York
Series title:
Water-Resources Investigations Report
Series number:
85-4013
Edition:
-
Year Published:
1986
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
viii, 103 p. :ill., maps ;28 cm.