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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
BackgroundThe 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. ACWI and its subcommittees were deactivated in 2019, but the NGWMN still exists and is maintained by the USGS. 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 DesignThe 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.
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: 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: 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).
Network StatusA pilot phase that started in 2009 initially populated the network with data from 5 pilot networks. 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. |
