- Groundwater is the primary source of freshwater in streams, lakes, and wetlands, and maintains the saline balance of estuaries. When large amounts of groundwater are withdrawn the water table is locally depressed and reduces the amount of groundwater available to discharge to streams and estuaries. Large-scale sewering practices have also reduced groundwater levels and discharge to surface receiving waters.
Groundwater quality on Long Island has been impaired by saltwater intrusion and human activities. Increased saltwater intrusion from groundwater pumping has occurred in the Lloyd and Magothy aquifers on western Long Island since the 1940s (Cartwright, 2002) and in Suffolk County since the 1970s (Nemickas and Kozalka, 1982).
Contamination by human activities can be from point sources such as industrial and commercial facilities or diffuse sources such as domestic wastewater, road salt, fertilizers, pesticides, etc. Of particular concern, in Suffolk County, is the return of domestic wastewater to groundwater from septic systems.