Hydrogeologic conditions in the coastal plain of New Jersey

Abstract

A wedge-shaped mass of unconsolidated sediments composed of alternating layers of clay, silt, sand, and gravel underlies the Coastal Plain of New Jersey. The hydrologic units of this mass vary in thickness, lateral extent, lithology, and water-bearing characteristics. Some of the units act as aquifers, whereas other units act as confining layers. The entire sediment wedge is almost an independent and isolated hydrologic system. Components of the long-term hydrologic budget for the Coastal Plain are precipitation, streamflow, and water loss. Under natural conditions, average precipitation is about 44 inches per year; while streamflow and water loss are about 20 and 24 inches per year, respectively. More than 75 percent of the streamflow in the Coastal Plain is derived from ground-water runoff. Some activities of man have modified the natural hydrologic cycle in the Coastal Plain. The primary activity affecting the system has been the withdrawal of ground water. Major changes in the flow patterns of water in several aquifers have been recognized during the past few decades partially as a result of increasing ground-water withdrawal. Where head gradients are large enough, water can be induced to flow from adjacent surface-water bodies or through confining beds. Induced recharge from the Delaware River to the Potomac-Raritan-Magothy aquifer system is occurring as a result of pumping stresses in the outcrop area of the aquifer. Recharge from the river to the aquifer from Salem to Burlington County was estimated to be about 113 cubic feet per second in 1978. (USGS)