Hydrologic appraisal of the Pine Barrens, Suffolk County, New York

The groundwater resources of the Pine Barrens, in southeastern Suffolk County, were appraised during 1982-83 for their potential for use as a supply of potable water. The study area encompasses approximately 50 square miles. The Precambrian bedrock is overlain by Cretaceous, Pleistocene, and Holocene deposits. The surficial material consists of morainal and outwash deposits overlain by recent beach and marsh deposits. The groundwater reservoir consists of three aquifers--the Lloyd and the Magothy of Cretaceous age and the upper glacial of Pleistocene age. The water is generally of suitable quality for drinking and most other uses except in several localized spots where point-source contamination has been documented. Precipitation is the sole source of recharge. Average annual precipitation recorded in the area during 1943-82 was 43 inches, about half of which reaches the groundwater reservoir. Overland runoff is estimated to be 0.5 inches per year, and evapotranspiration 23 inches per year. Total public water-supply withdrawal in the area in 1982 is estimated to have been 9.09 million gallons per day (Mgal/d). The upper glacial aquifer is the major source of public water; pumpage in 1982 was 7.88 Mgal/d; pumpage from the Magothy was 1.02 Mgal/d, and pumpage from the Lloyd aquifer was 0.19 Mgal/d. Stream discharge is measured periodically at 17 streamflow measurement sites on the 11 streams in the Pine Barrens. (USGS)