One of the most important concepts to understand is that volumes of water pumped from a groundwater system must come from somewhere and must cause a change in the groundwater system. Another important concept is that water table aquifers are hydraulically connected to the streams that drain them. Therefore, pumping water from aquifers that are hydraulically connected with surface-water bodies can have a significant effect on those bodies by reducing groundwater discharges to surface water and possibly causing outflow from those bodies into the groundwater system. Thus, an evaluation of groundwater management strategies needs to involve consideration of surface-water resources, including closely related biological resources.
A key feature of Long Island’s groundwater system is the large volume of groundwater in storage, which allows the possibility of using aquifers for temporary storage, that is, managing inflow and outflow of groundwater in storage in a manner similar to surface-water reservoirs (Alley and others, 1999). The groundwater reservoir of Long Island is a wedged shaped mass of saturated unconsolidated deposits that overlie nearly impermeable consolidated bedrock and attain a maximum thickness of about 2,000 feet. The boundaries of the fresh groundwater reservoir are the water table, the fresh-salt water interfaces, the bedrock surface, and the streams. The estimated volume of material saturated with fresh groundwater is about 180 cubic miles, and an estimated 10-20 trillion gallons of freshwater would drain from these deposits if they could be completely dewatered (Franke and others, 1972).
From the standpoint of water use and water management, all groundwater is not equal--the suitability of water, as measured by its quality, is a key consideration in developing water-management strategies. Furthermore, determining water suitability (or unsuitability) requires detailed information on the three-dimensional distribution and concentrations of potential contaminants, both naturally occurring contaminants and those resulting from human activities (Alley and others, 1999).
Continued large withdrawals of water from an aquifer often result in undesirable consequences. From a management standpoint, water managers, stakeholders, and the public must decide the specific conditions under which the undesirable consequences can no longer be tolerated.
The effects of groundwater development may require many years to become evident. Thus, there is an unfortunate tendency to forego the data collection and analysis that is needed to support informed decision making until well after problems materialize (Alley and others, 1999).
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Table of Contents
State of the Aquifer, Long Island, New York - Introduction
- Precipitation
- NWIS - the USGS Data Archive
- Surface Water - Streamflow
- Groundwater Levels
- Water Table and Surface Maps
- Water Use
- Groundwater Budget
- Inflow to the Groundwater System
- Outflow from the Groundwater System
Below are other science projects associated with this project.
Long Island Water Availability
Long Island Precipitation
NWIS - the USGS Data Archive
Long Island Surface Water - Streamflow
Long Island Groundwater Levels
Long Island Water Table and Surface Maps
Long Island Water Use
Long Island Groundwater Budget
Long Island Inflow to the Groundwater System
Long Island Outflow from the Groundwater System
Long Island Water Suitability
Long Island Water Suitability Case Studies
- Overview
One of the most important concepts to understand is that volumes of water pumped from a groundwater system must come from somewhere and must cause a change in the groundwater system. Another important concept is that water table aquifers are hydraulically connected to the streams that drain them. Therefore, pumping water from aquifers that are hydraulically connected with surface-water bodies can have a significant effect on those bodies by reducing groundwater discharges to surface water and possibly causing outflow from those bodies into the groundwater system. Thus, an evaluation of groundwater management strategies needs to involve consideration of surface-water resources, including closely related biological resources.
A key feature of Long Island’s groundwater system is the large volume of groundwater in storage, which allows the possibility of using aquifers for temporary storage, that is, managing inflow and outflow of groundwater in storage in a manner similar to surface-water reservoirs (Alley and others, 1999). The groundwater reservoir of Long Island is a wedged shaped mass of saturated unconsolidated deposits that overlie nearly impermeable consolidated bedrock and attain a maximum thickness of about 2,000 feet. The boundaries of the fresh groundwater reservoir are the water table, the fresh-salt water interfaces, the bedrock surface, and the streams. The estimated volume of material saturated with fresh groundwater is about 180 cubic miles, and an estimated 10-20 trillion gallons of freshwater would drain from these deposits if they could be completely dewatered (Franke and others, 1972).
From the standpoint of water use and water management, all groundwater is not equal--the suitability of water, as measured by its quality, is a key consideration in developing water-management strategies. Furthermore, determining water suitability (or unsuitability) requires detailed information on the three-dimensional distribution and concentrations of potential contaminants, both naturally occurring contaminants and those resulting from human activities (Alley and others, 1999).
Continued large withdrawals of water from an aquifer often result in undesirable consequences. From a management standpoint, water managers, stakeholders, and the public must decide the specific conditions under which the undesirable consequences can no longer be tolerated.
The effects of groundwater development may require many years to become evident. Thus, there is an unfortunate tendency to forego the data collection and analysis that is needed to support informed decision making until well after problems materialize (Alley and others, 1999).
_______________________________
Table of Contents
State of the Aquifer, Long Island, New York - Introduction
- Precipitation
- NWIS - the USGS Data Archive
- Surface Water - Streamflow
- Groundwater Levels
- Water Table and Surface Maps
- Water Use
- Groundwater Budget
- Inflow to the Groundwater System
- Outflow from the Groundwater System
- Science
Below are other science projects associated with this project.
Filter Total Items: 13Long Island Water Availability
The foundation of any groundwater analysis, including those analyses whose objective is to propose and evaluate alternative management strategies, is the availability of high-quality data. Some, such as precipitation data, are generally available and relatively easy to obtain at the time of a hydrologic analysis. Other data and information, such as geologic and hydrogeologic maps, can require...Long Island Precipitation
The National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC) offers several types of climate information generated from examination of the data in the archives. These types of information include record temperatures, record precipitation and snowfall, climate extreme statistics, and other derived climate products. A collection of statistical weather and climate...NWIS - the USGS Data Archive
As part of the U.S. Geological Survey's (USGS) program for disseminating water data within USGS, to USGS cooperators, and to the general public, the USGS maintains a distributed network of computers and fileservers for the acquisition, processing, review, and long-term storage of water data. This water data is collected at over 1.5 million sites around the country and at some border and...Long Island Surface Water - Streamflow
Surface water current conditions are based on the most recent data from on-site automated recording equipment. Measurements are commonly recorded at a fixed interval of 15 to 60 minutes and transmitted by satallite uplink or telephone telemetry to the USGS every hour. Values may include "Approved" (quality-assured data that may be published) and/or more recent "Provisional" data (of unverified...Long Island Groundwater Levels
Water-level measurements from observation wells are the principal source of information about the hydrologic stresses acting on aquifers and how these stresses affect groundwater recharge, storage, and discharge (Taylor and Alley, 2001). Water-level measurements are made by many Federal, State, and local agencies.Long Island Water Table and Surface Maps
The depth to the water table can be determined by installing wells that penetrate the top of the saturated zone just far enough to respond to water table fluctuations. Preparation of a water-table map requires that only wells that have their well screens installed near the water table be used. If the depth to water is measured at a number of such wells throughout an area of study, and if those...Long Island Water Use
The U.S. Geological Survey's National Water-Use Information Program (NWUIP) is responsible for compiling and disseminating the nation's water-use data. The USGS works in cooperation with local, State, and Federal environmental agencies to collect water-use information. USGS compiles these data to produce water-use information aggregated at the county, state, and national levels. Every five years...Long Island Groundwater Budget
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...Long Island Inflow to the Groundwater System
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...Long Island Outflow from the Groundwater System
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...Long Island Water Suitability
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.Long Island Water Suitability Case Studies
A collection of studies that focused on the quality of groundwater and surface water, are presented in this section. The reports associated with these areas of water quality concerns are linked as an online source for further reading.