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Analysis of three tests of the unconfined aquifer in southern Nassau County, Long Island, New York

Water-Resources Investigations Report 82-4021

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Abstract

Drawdown and recovery data from three 2-day aquifer tests (OF) the unconfined (water-table) aquifer in southern Nassau County, N.Y., during the fall of 1979, were analyzed. Several simple analytical solutions, a typecurve-matching procedure, and a Galerkin finite-element radial-flow model were used to determine hydraulic conductivity, ratio of horizontal to vertical hydraulic conductivity, and specific yield. Results of the curve-matching procedure covered a broad range of values that could be narrowed through consideration of data from other sources such as published reports, drillers ' logs, or values determined by analytical solutions. Analysis by the radial-flow model was preferred because it allows for vertical variability in aquifer properties and solves the system for all observation points simultaneously, whereas the other techniques treat the aquifer as homogeneous and must treat each observation well separately. All methods produced fairly consistent results. The ranges of aquifer values at the three sites were: horizontal hydraulic conductivity, 140 to 380 feet per day; transmissivity 11,200 to 17,100 feet squared per day; ratio of horizontal to vertical hydraulic conductivity 2.4:1 to 7:1, and specific yield , 0.13 to 0.23. (USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Analysis of three tests of the unconfined aquifer in southern Nassau County, Long Island, New York
Series title:
Water-Resources Investigations Report
Series number:
82-4021
Edition:
-
Year Published:
1982
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
v, 51 p. :ill., map ;28 cm.