Water-table and potentiometric-surface altitudes of the upper glacial, Magothy, and Lloyd aquifers on Long Island, New York, in March-April 1997, with a summary of hydrogeologic conditions

Abstract

Water-table and potentiometric-surface altitudes of the three main water-bearing units on Long Island-the upper glacial (watertable) aquifer and the underlying Magothy and Lloyd aquifers-were contoured from waterlevel measurements made at 666 observation, public-supply and industrial-supply wells during March-April1997. Changes in water-level altitudes since 1990 ranged from an increase of 5.42 ft in the water-table aquifer in eastcentral Queens County to a decrease of 10.99 ft in the Magothy aquifer in central Nassau County. In general, water-level altitudes in the upper glacial (water-table) and Magothy aquifers have declined throughout most parts of the island since 1990, but have risen in central and eastern Queens County and extreme southwestern Nassau County. Altitudes in the Lloyd aquifer have risen throughout most of western Long Island and have declined in the central and eastern parts since 1990.