Groundwater Flow Modeling

Numerical models provide a means to synthesize existing hydrogeologic information into an internally consistent mathematical representation of a real system or process, and thus are useful tools for testing and improving conceptual models or hypotheses of groundwater flow systems. The goal of this effort is to develop a regional model for the Long Island aquifer system to simulate changes in water...

The U.S. Geological Survey (USGS) has partnered with the New York State Department of Environmental Conservation (NYSDEC) to conduct a comprehensive study of the Long Island aquifer system. The major findings of this investigation include: The location of the boundary between fresh and salty groundwater is much closer to the shoreline than previously thought. The historical onshore saltwater...

Long Island is underlain by unconsolidated Holocene deposits, glacial deposits of Pleistocene age, and coastal-plain deposits of Late Cretaceous age. These sediments consist of gravel, sand, silt, and clay underlain by crystalline bedrock of early Paleozoic age (figure 2b). The bedrock is relatively impermeable, and forms the base of the groundwater-flow system on Long Island. The geologic and...

Saltwater intrusion is the most common type of water-quality degradation in coastal-plain aquifers. In coastal areas, the hydraulic head under predevelopment (nonpumping) conditions is higher on land than in the surrounding saltwater embayments; thus, fresh groundwater flows seaward (from areas of high potential to areas of lower potential) and meets saltwater at an equilibrium point (interface)...

Background For effective wellhead protection, the area where water carrying potential contaminants can enter the groundwater system and flow to the supply well must first be defined, and then best management practices need to be implemented to minimize the opportunity for contamination to occur in areas defined as sources of water to the well. Determination of the sources of water and contributi

The U.S. Geological Survey (USGS) is a science organization that provides impartial information on the health of our ecosystems and environment, the natural hazards that threaten us, the natural resources we rely on, the impacts of climate and land-use change, and the core science systems that help us provide timely, relevant, and usable information.

Problem The Peconic Estuary of eastern Long Island, New York, is undergoing development as the region transitions from a rural area dependent on agriculture and tourism to a suburban one with a larger year-round population. The glacial and coastal-plain sediments underlying Long Island comprise a sole-source aquifer system that supplies the region’s communities with potable water. The area surrou

Long Island, the eastern-most part of New York State, extends east-northeastward roughly parallel to the Connecticut coastline. It is bounded on the north by Long Island Sound, on the east and south by the Atlantic Ocean, and on the west by New York Bay and the East River. Long Island is joined to the mainland specifically, to the Borough of the Bronx, which is one of the five boroughs of New York...

A groundwater system consists of a mass of water flowing through the pores or cracks below the Earth's surface. This mass of water is in constant motion. Water is constantly added to the system by recharge from precipitation, and water is constantly leaving the system as discharge to surface water and as evapotranspiration. Each groundwater system is unique in that the source and amount of water...

Precipitation that infiltrates and percolates to the water table is Long Island's only natural source of freshwater because the groundwater system is bounded on the bottom by relatively impermeable bedrock and on the sides by saline ground water or saline bays and the ocean. About one-half the precipitation becomes recharge to the groundwater system; the rest flows as surface runoff to streams or...

The flow of water leaving, or discharging, the groundwater system of Long Island occurs naturally through streams, as base flow, at the coastline as shoreline discharge and sub-sea discharge, and through pumping wells as withdrawals. Estimates of each component of outflow from the groundwater system is presented and summarized in this section using streamflow measurements, and a compilation of...

Groundwater quality may be affected by natural and human factors (Johnston, 1988). Although the vulnerability of groundwater to contamination from the land surface is influenced by many factors, the degree of aquifer confinement, the depth of the well, and the surrounding land use are primary key factors that influence shallow groundwater quality.