Long Island Groundwater Levels

Science Center Objects

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.

The Active Groundwater Level Network contains water levels and well information from more than 20,000 wells that have been measured by the USGS or USGS cooperators at least once within the past 13 months. These wells are measured for a variety of disparate purposes, such as statewide monitoring programs, or more local effects like monitoring well drawdown, hydrologic research, aquifer tests, or even earthquake effects on water levels.

Source: http://groundwaterwatch.usgs.gov/statemap.asp?sc=36&sa=NY

On Long Island and in the five boroughs of New York City the USGS operates over 600 active groundwater data-collection stations that provide long-term, accurate, and unbiased information that meets the needs of many diverse users. Details of the current groundwater monitoring on Long Island and the five boroughs of New York City are available at http://ny.water.usgs.gov/projects/LI_PRJ/.


map of Nassau county NY groundwater well network
Figure 20. An example map of groundwater watch locations for Nassau County, New York.(Public domain.)

These "groundwater watch" web pages group related wells and data from these active well networks, and provide basic statistics about the water-level data collected by USGS water science centers for Cooperative Programs, for Federal Programs, and from data supplied to us by our customers through cooperative agreements. USGS Groundwater Watch is maintained by the Office of Groundwater, and more groundwater watch web pages are available at http://groundwaterwatch.usgs.gov/ (figure 20). In addition to the active groundwater level network, all groundwater watch web pages for New York are available here: "Real-Time Groundwater Level Network" , "Below Normal Groundwater Levels" , "Long-Term Groundwater Data Network" or "Climate Response Network."

The groundwater database within NWIS contains records from about 850,000 wells Nationwide that have been compiled during the course of groundwater hydrology studies over the past 100 years. Information from these wells is served via the Internet through the National Water Information System Web Interface, NWISWeb. NWISWeb provides all USGS groundwater data that are approved for public release. This large number of sites is excellent for some uses, but complicates retrievals when the user is interested in specific networks, or wells in an active water-level measurement program. The National Water Information System Web Interface, NWISWeb provides all USGS groundwater data that are approved for public release. Groundwater 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 satellite uplink or telephone to the USGS every hour. Values may include "Approved" (quality-assured data that may be published) and/or more recent "Provisional" data (of unverified accuracy and subject to revision).

Out of about 100 sites in New York, there are over 10 sites on Long Island that provide current data collection, which is mostly provisional. The data can be found by clicking on this link groundwater current conditions or viewed in a map interface to download data.

Historical instantaneous groundwater data from these sites are also available. A summary of all data for each day (daily data) for the period of record and may represent the daily mean, median, maximum, minimum, and/or other derived value is available at about 50 groundwater sites on Long Island. Values may include "Approved" (quality-assured data that may be published) and/or more recent "Provisional" data (of unverified accuracy and subject to revision).

Manual measurements of depth to water in wells are used to supplement and (or) verify the accuracy of the automatically recorded observations. There are over 4,300 groundwater sites on Long Island that can be selected which have at least one water level measurement (depth to water measurement).

Statistics are computed from approved daily mean data at each site. Statistical summaries of approved historical daily values for daily, monthly, and annual (water year or calendar year) time periods are also available. There are around 50 groundwater sites on Long Island, with daily, monthly, or annual statistics of the measured groundwater elevation in feet above NGVD 1929.



Table of Contents

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

Location and Physical Setting


  1. Hydrolgeologic Units
  2. Fresh and Saltwater Relations/Interactions

State of the Aquifer System

  1. Precipitation
  2. NWIS - the USGS Data Archive 
  3. Surface Water - Streamflow
  4. Groundwater Levels
  5. Water Table and Surface Maps
  6. Water Use
  7. Groundwater Budget
  8. Inflow to the Groundwater System
  9. Outflow from the Groundwater System
  1. Case Studies

Interactive Content