Water levels in Nassau County Sewer Districts 2 and 3, Long Island, New York, 1978-79

Prior to development on Long Island, about 95 percent of total streamflow originated as groundwater seepage from the upper glacial aquifer; the remaining 5 percent consisted of direct storm runoff. Thus, the streams on Long Island function as groundwater drains. Their flow in dry weather is directly controlled by groundwater levels adjacent to the stream channels. Sewage systems in Nassau County have caused a general lowering of groundwater levels, which in turn has severely reduced streamflow. This report presents monthly water-level measurements in 259 wells in Nassau county from 1978-79 to provide a data base to evaluate the need to replace streamflow lost through lowering of the water table. (USGS)