The National Ground-Water Monitoring Network (NGWMN) is a compilation of selected wells monitoring groundwater aquifers all around the nation. The NGWMN Data Portal brings groundwater data together in one place to provide users with current and reliable information for the planning, management, and development of groundwater resources.

About the Network


The NGWMN network was sponsored by the Advisory Committee on Water Information's (ACWI) Subcommittee on Ground Water (SOGW) and was established in 2009 with a pilot network.

The goal of the National Ground-Water Monitoring Network (NGWMN) is to provide information needed for planning, management, and development of groundwater supplies to meet current and future water needs and ecosystem requirements. This will be accomplished by aggregating suitable groundwater data from local, State, and Federal organizations. A consensus-based  framework document was developed to provide guidance to ensure that the data are comparable and can be included in a nationally consistent network. The framework design focuses on providing information needed to assess the quantity of groundwater reserves as constrained by quality. The scale of the network focuses on Principal and Major Aquifers of the United States.

Network Design

The network is composed of selected wells from existing Federal, multi-state, State, Tribal, and local groundwater monitoring networks. The focus of the NGWMN is the water levels and water quality of the Principal and Major Aquifers of the United States. Well classification subnetworks and monitoring categories are defined in the  framework document  and are briefly described here:

Well Classification Subnetworks:

Wells in the NGWMN will be designated as being in one of three subnetworks. These are 1) the Background subnetwork, 2) the Suspected Changes subnetwork, and 3) the Documented Changes subnetwork.

Background subnetwork:

Monitoring points that provide data from aquifers or parts of aquifers with no (or minimal) anthropogenic effects. These are from areas that have been minimally affected by human activities and are expected to remain so.

Suspected Changes subnetwork:

Monitoring points that provide data from aquifers or parts of aquifers that may have been affected by man's activity, but that is not documented or conclusive. These wells may also be in areas where changes are anticipated. These may be areas with withdrawals are occurring or where land-use has changed, but the effect has not yet been clearly identified.

Documented Changes subnetwork:

Monitoring points that provide data from aquifers that have documented anthropogenic effects. The aquifers may: 1) be known to be heavily pumped 2) have experienced substantial recharge-altering land-use changes 3) have managed groundwater resources 4) are known to have degraded water quality or declining water levels.

Baseline Process:

The baseline process is required of all wells to provide or identify an initial monitoring record that is used to place the well into one of the above subnetworks. Five years of monitoring is generally considered adequate to establish these conditions. For existing wells, past data may be used to categorize wells into one of the subnetworks.

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Monitoring Categories:

Wells within each subnetwork (Background, Suspected Changes, or Documented Changes) will be assigned to a monitoring category depending on the purpose of the monitoring at the well. These categories, and conditions at the wells, will be used to determine suggested monitoring frequencies.


Trend wells are generally monitored to determine changes over time. The frequency of monitoring depends on the hydrologic conditions of the aquifer and can range from daily data to annual measurements. A subset of the trend monitoring wells will be designated as the "backbone" wells of the NGWMN.


Surveillance monitoring would be used in conjunction with Trend monitoring to periodically report on the overall water-level and water-quality conditions, or status, of the Nation's groundwater resources. NGWMN Surveillance monitoring can be thought of as a periodic "census" of groundwater level and quality. An overall snapshot of groundwater conditions in an aquifer is obtained with Surveillance monitoring. The frequency of Surveillance monitoring generally is much less than Trend monitoring.

Special Studies:

Special studies monitoring is a secondary aspect of the NGWMN. This monitoring is not required and is only provided as an option. Special studies monitoring would be most often associated with the Suspected or Documented Changes Subnetworks and would be used to evaluate the status of ground-water resources at risk, or potential risk, from depletion or impairment. The monitoring frequency would vary, depending on the study. Categorizing wells as special studies acts as a flag to indicate that additional information might be available because wells are measured or sampled for a special purpose regionally or nationally (for example, wells measured to observe the effects of hydraulic fracturing).

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Network Status

A pilot phase that started in 2009 initially populated the network with data from 5 pilot networks. These pilots were: the Mahomet-Teays aquifer in Illinois and Indiana, the Cambrian-Ordovician aquifer in southeastern Minnesota, and Principal and Major Aquifers in Montana, New Jersey, and Texas.

Reports from these 5 pilots and a summary report of the pilot effort are available below:

Following the pilot phase, additional USGS water-level monitoring wells that met the network criteria were added to the NGWMN for some states. In 2015, the Network received funding and began implementation.

The Data Portal

The Data Portal

The NGWMN Data Portal is the access point for information about the wells in this network and for their related lithology (geology), construction, water-level and water-quality data. To access the portal click here. To learn how to use the portal click here.

An important aspect of the NGWMN Data Portal is that it is not an aggregated database of data from all participants, but is a gateway to the data which are maintained and served by each participating organization. Original data are retrieved from each data provider by the portal. Data from each provider is refreshed nightly to create a cached data set to allow queries to the data to be faster. These data are then transformed into a consistent format to serve out to the NGWMN Data Portal. 

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The Data Portal has filters and map-based selection capabilities that allow the user to select the sites of interest. After the sites are selected, requests are sent to cached database to obtain the data. 

Queries can be made on network type (Water Level or Water Quality), well classification, and monitoring category. Sites can also be queried based on Principal Aquifer, type of data available, contributing agency, and state/county.

Development work on the portal is proceeding according to a  5-year plan created in 2018. 

Web Services

Web service requests may be submitted to obtain data directly and to bypass the NGWMN map interface. Currently only basic site information and water levels are available through web service requests. For full site information, lithology, construction information or water quality data visit the NGWMN Data Portal. For more information on the NGWMN Web Services, see the Web Services Guide.


Booth, N.L., Brodaric, B., Lucido, J.M., Kuo, I.-L., Boisvert, E., and Cunningham, W.L., 2011, Development of an Interoperable Groundwater Data Exchange Network between the United States and Canada, in GeoHydro 2011 Conference Proceedings Paper. URL:

Blodgett, D., Read, E., Lucido, J., Slawecki, T., and Young, D., 2016, An Analysis of Water Data Systems to Inform the Open Water Data Initiative: JAWRA Journal of the American Water Resources Association, v. 52, no. 4, p. 845-858. DOI:10.1111/1752-1688.12417

Larsen, S., Hamilton, S., Lucido, J., Garner, B., and Young, D., 2016, Supporting Diverse Data Providers in the Open Water Data Initiative: Communicating Water Data Quality and Fitness of Use: JAWRA Journal of the American Water Resources Association, v. 52, no. 4, p. 859-872. DOI:10.1111/1752-1688.12406

Blodgett, D., Lucido, J., and Kreft, J., 2015, Progress on water data integration and distribution: a summary of select U.S. Geological Survey data systems: Journal of Hydroinformatics, v. 18, no. 2, p. 226-237. DOI:10.2166/hydro.2015.067

Brodaric, B., Booth, N., Boisvert, E., and Lucido, J., 2015, Groundwater data network interoperability: Journal of Hydroinformatics, v. 18, no. 2, p. 210-225. DOI:10.2166/hydro.2015.242

Data Providers

The National Ground-Water Monitoring Network (NGWMN) is a compilation of selected groundwater monitoring wells from Federal, State, and local groundwater monitoring networks across the nation. The following agencies are currently contributing to the NGWMN.

The agencies listed below are currently providing data to the NGWMN. 

Geological Survey of Alabama

Alaska Department of Natural Resources

Arizona Department of Water Resources

Water Replenishment District of Southern California

Colorado Department of Water Resources

Delaware Geological Survey

Florida Department of Environmental Protection

Illinois State Water Survey

Indiana Geological and Water Survey 

Iowa Department of Natural Resources

Iowa Geological Survey

Kansas Geological Survey

Maine Geological Survey

Minnesota Department of Natural Resources

Minnesota Pollution Control Agency

Mississippi Department of Environmental Quality

Montana Bureau of Mines and Geology

Nebraska, Conservation and Survey Division

Nebraska Department of Environment and Energy

New Hampshire Geological Survey

New Mexico Institute of Mining and Technology

North Carolina Department of Environmental Quality

Oklahoma Water Resources Board

Oregon Water Resources Department

South Carolina Department of Natural Resources

Suwanee River Water Management District-Florida

St. Johns River Water Management District-Florida

Texas Water Development Board

U.S. Geological Survey

Utah Geological Survey

Washington State Department of Ecology

Wyoming Department of Environmental Quality

Pending Data Providers

The following agencies are in the process of becoming a data provider to the NGWMN:

Grand County, Utah

Kentucky Geological Survey

Michigan Department of Environment, Great Lakes, and Energy

Presidio County Texas Groundwater District

USGS Cooperative Match Funds Projects Data Providers

The following agencies are NGWMN data providers through USGS Cooperative Matching Funds Monitoring programs with their local USGS Water Science Center. Information about data collection and data management procedures for these agencies are presented under the USGS Data Provider Page.  Specifics of past projects with these agencies are also shown on the  USGS Data Provider Page.

Massachusetts Department of Conservation and Recreation

Massachusetts: Cape Cod Commission

Missouri Department of Natural Resources

New Jersey Department of Environmental Protection

Ohio Department of Natural Resources

Wisconsin Geologic and Natural History Survey

Resources for New Data Providers:

Information about USGS cooperative agreements to fund data providers is available here.

The National Ground-Water Monitoring Network focuses on Principal Aquifers. Principal Aquifers are defined by the USGS in the Ground Water Atlas.

Principal Aquifers of the United States

Map of the Principal Aquifers of the United States

GIS Resources:

Shapefiles of the 'Principal Aquifers of the United States' and the 'Aquifers of Alluvial and Glacial Origin' are available here.

A shapefile of the sites in the NGWMN as of November 6, 2023 is available here.

GIS layers in multiple formats of sites and the most-recent water level percentiles can be found on the Geoserver page.

New Data Provider Tip Sheets:

Tip Sheet on Well Selection Criteria for Water Levels 

Tip Sheet on Well Selection Criteria for Water Quality

Tip Sheet on Defining the "Subnetwork"

Tip Sheet on Defining Monitoring Categories 

Tip Sheet on Populating the Monitoring Location Registry

Tip Sheet on Minimum Data Requirements for Candidate Sites

Tip Sheet on Web Service Development

Wyoming DEQ Tip Sheet on creating ARCGIS server web services

Tip Sheet on Standard Elements for Water-Quality web services

NGWMN Data Dictionary

General Tip Sheets:

How to Cite NGWMN Data

Monitoring Location Registry Documentation

Monitoring Location Registry Field Definitions

Creating Shapefiles of NGWMN sites

Viewing Water-Level Statistics in the NGWMN Data Portal

Other Resources:

A spreadsheet showing the suggested density of water-level and water-quality sites by state and Principal aquifer is available here.

The NGWMN Well Registry Management System can be accessed here.

Get Involved

The NGWMN is actively seeking data providers for the Network. Data providers work with the USGS to set up connections between their databases and the NGWMN Data Portal to pass data to the Network as needed. The data providers also work with the USGS to select and classify wells for the Network.

Information on a funding opportunity available to assist state or local water-resource agencies in becoming data providers is available here