Long Island Water Use

By New York Water Science Center May 11, 2017

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, data at the county level are compiled into a national water-use data system and state-level data are published in a national circular. Over the history of these circulars, the water-use categories have had some changes.

Data from these national circulars are represented as an interactive map interface from 1985-2005 at 5 year intervals. A table of water use data for each county on Long Island can be viewed.

Source: TABLE 1985-2005 NWUIP DATA USED

Interactive map interface of 5-yr water use data:

Interactive Map - 1985
Interactive Map - 1990
Interactive Map - 1995
Interactive Map - 2000
Interactive Map - 2005
Interactive Map - 2010

Public Water Supply Districts

Public water supply refers to water withdrawn by public and private water suppliers that provide water to at least 25 people or have a minimum of 15 connections. Public-supply water is delivered to users for domestic, commercial, and industrial purposes, and also is used for public services and system losses. In New York State, the law requires any water withdrawal system with a capacity of 100,000 gallons per day or more to obtain a permit and send annual reports to the New York State Department of Environmental Conservation (NYSDEC).

Between 70-80% of all the groundwater withdrawn beneath Long Island has been withdrawn for public supply usage for the 1985-2005 period. The responsibility of the water supply companies in Nassau and Suffolk Counties are shared between over 50 supply companies who are members of the Long Island Water Conference. These companies utilized over 1,100 large capacity wells to supply potable water to a population of over 2.6 million, and to light industries, such as office parks and other commercial business. The figure below represents a generalized distribution of supply wells that pumped water between 2007 and 2010, and are considered as active supply wells (figure 22).

An interactive map of the water supply company service areas shows the generalized outline of the individual supply company service areas on Long Island. Withdrawal data reported to the NYSDEC, by law, was compiled to represent the most recent year’s average withdrawals over a calendar year. Over 415 Mgal/d total average annual withdrawal was reported for the 2010 calendar year. There were some supply areas where the 2010 withdrawal data was not available (at this time); however previous years withdrawals may give a rough estimate of the average withdrawals for that area. When 2010 withdrawal data were available an aquifer breakdown is shown as a pie chart. Island wide over 75% of the average 2010 groundwater withdrawals were from the Magothy aquifer.

map of of over 1,100 large capacity supply wells on Long Island — Figure 22. Generalized location of over 1,100 large capacity supply wells used since 2007(Public domain.)

The trends in public supply withdrawals tend to follow population trends. The bar graph below represents the withdrawals reported to the NYSDEC from 1988-2010, in Nassau and Suffolk Counties (figure 23). There are instances when withdrawals are not reported, and are not represented in these annual totals; however these amounts are presumed to be a small percentage of the total public-supply withdrawals. The public supply annual withdrawal average from 2005 to 2010 was about 380 Mgal/d for Nassau and Suffolk Counties.

graph of annual public supply well withdrawals for Nassau and Suffolk Counties — Figure 23. Graph of annual withdrawals for Nassau and Suffolk Counties, averaged daily from 1988-2010 (Source: New York State Department of Conservation).(Public domain.)

Seasonal reported withdrawals from 1988-2009 in Nassau County is represented in the bar graphs below (figure 24); the data used was provided by the Nassau County Department of Public Works. The monthly variability shows a cyclical pattern with the summer months average withdrawal rates ranging from 220 to over 340 Mgal/d; and the winter months ranging from 130 to 150 Mgal/d. The seasonal trend lines indicate a decreasing rate of withdrawal in the winters and an increasing rates of withdrawals in the summers, from 1988-2009.

Graph of Nassau County total average monthly public water supply withdrawals — Figure 24. Graph of Nassau County total average monthly withdrawals, averaged daily from 1988-2009 (Source: Nassau County Department of Public Works).(Public domain.)

Seasonal reported withdrawals from 1988-2009 in Suffolk County represented in the bar graphs below (figure 25); the data used was provided by the Suffolk County Water Authority which serves groundwater to approximately 1.2 million people or 80 percent of the Suffolk County’s population. The monthly variability shows a cyclic pattern with the summer months average withdrawal rates ranging between 160 to over 360 Mgal/d; and the winter months ranging between 80 to 100 Mgal/d. The seasonal trend lines indicate a increasing rate of withdrawal in the winters and an increasing rates of withdrawals in the summers, from 1988-2009.

Figure 25. Graph of Suffolk County Water Authority monthly withdrawal, averaged daily from 1988-2009 (Source: Suffolk County Water Authority).(Public domain.)

Domestic-Self Supply

Self-supplied domestic water use is usually withdrawn from a private source, such as a well, or captured as rainwater in a cistern; in the United States 14 percent of the population, supplied their own water for domestic use in 2005. However on Long Island, about 200,000 people were estimated to have been using private domestic well water which totaled about 15 Mgal/d, in 2005 (Kenny and others, 2009).

Irrigation

Irrigation water use includes water that is applied by an irrigation system to sustain plant growth in all agricultural and horticultural practices. Irrigation also includes water that is applied for pre-irrigation, frost protection, application of chemicals, weed control, field preparation, crop cooling, harvesting, dust suppression, leaching salts from the root zone, and water lost in conveyance. Irrigation of golf courses, parks, nurseries, turf farms, cemeteries, and other self-supplied landscape-watering uses also are included. Irrigation water use includes self-supplied withdrawals and deliveries from irrigation companies, irrigation districts, cooperatives, or governmental entities. In 2005, it was estimated that less than 10 Mgal/d was used for irrigation on Long Island (Kenny and others, 2009).

Commercial / Industrial-Self Supply

Industrial water use includes water used for such purposes as fabricating, processing, washing, diluting, cooling, or transporting a product; incorporating water into a product; or for sanitation needs within the manufacturing facility. Some industries that use large amounts of water produce such commodities as food, paper, chemicals, refined petroleum, or primary metals. Water for industrial use may be delivered from a public supplier or be self-supplied. In this website, industrial use refers to self-supplied industrial withdrawals only. In 2005, about 67 Mgal/d was used for industrial use across Long Island (Kenny and others, 2009).

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Table of Contents

State of the Aquifer, Long Island, New York - Introduction

Location and Physical Setting

Freshwater

State of the Aquifer System