National Groundwater Conditions Web Application

Groundwater is a critical resource for many people, and the USGS generates groundwater level data for thousands of sites across the United States and outlying territories. The ability to put current groundwater data into a long-term historical context is valuable in understanding trends in groundwater use at a particular monitoring location, region, or at the national scale. In 2022, the web application Groundwater Watch was shut down and a long-term replacement is in development. Here, we introduce National Groundwater Conditions, a national-scale web application that maps active groundwater levels and enables users to explore site-level groundwater data with a historical context. The application provides information for understanding long-term trends in groundwater availability at a particular site and for managing critical groundwater resources. It delivers the core functionality that was previously available in Groundwater Watch.

This tool is being released as an experimental product. In the future, the functionality available in the application will be integrated into our existing USGS water applications such as the National Water Dashboard and Monitoring Location Pages; these applications have a wealth of additional mapping features and functionality.

Data and Resources


Field Value
Contact Name USGS Computational Tools
Contact Email
Publication Date 2023-10-05
Data Collection Frequency As Needed
Preparation Method Current and historical groundwater data are fetched from the National Water Information System (NWIS) web service, and the National Ground-Water Monitoring Network (NGWMN) web service. Non-USGS NGWMN sites are assumed to be regularly monitoring groundwater levels, while only NWIS sites within the Active Groundwater Level Network (see 'aw' outputDataTypeCd), which includes sites with a water level measurement taken at least once within the past 13 months, are displayed in this application. Some exceptions apply. For example, sites part of an occasional data collection program, or sites for which there is pending funding for future measurements may be shown. Similarly, sites for which there was formerly funding for data collection may still be shown in the Active Groundwater Level Network. NWIS data is gathered using the dataRetrieval R package. 'Discrete' water level measurements are collected using the dataRetrieval::readNWISgwl function, which queries the NWIS USGS Groundwater Levels Web Service , a service that provides historical manually-recorded groundwater levels. For this query, the USGS parameter code '72019' is used, which corresponds to 'Depth to water level, feet below land surface' per the Groundwater Levels Web Service Documentation. 'Continuous' water level measurements are obtained from NWIS using the dataRetrieval::readNWISdv function, which queries the USGS Daily Values Site Web Service. When collecting these data, the '72019' parameter code is also used. For these data, both the 00001 (maximum) and 00003 (mean) Statistics Codes are collected. These data are compared, and the statistic code with more data is used for the subsequent percentile calculations. This step is taken as different regions measure and record their water depth data differently, with some using the maximum statistic code, and others making use of the mean statistic code. In the event of a tie (both data records have the same number of entries), the mean values are used. National-scale NWIS site percentile values are computed daily using the precompute package. Statistics computations, tables, and plots are computed using the HASP package. Data is fetched from web services using the dataRetrieval package. For the non-USGS NGWMN sites, the precompute package is used to request a shapefile with the latest water-level percentile information from the NGWMN itself, per instructions in this tip sheet. As a consequence, the percentile values for non-USGS NGWMN sites are calculated by NGWMN, per their statistics methods documentation. Similar to the NGWMN criteria, the NWIS data at a site must have at least 10 years of data for the given month in order to be given a percentile rank. Sites with a historical record shorter than 10 years for a particular month are not ranked at this time. Note: Data shown on the national map are refreshed daily, and may not reflect the most recently collected values. In contrast, the individual site pages (accessed via link in the site pop-up, or from the summary table below the map) do access and display the latest and most up-to-date information for a given site.
Data Publishing Method Webmap
Data Publishing Frequency Daily
Geographic Location United States
Data Source National Water Information System (NWIS) web service and the National Ground-Water Monitoring Network (NGWMN) web service
Last Updated 27 November 2023
Published 27 November 2023