Ten IWS Basins are planned for intensive monitored by the Next Generation Water Observing Systems Program and are anticipated to be the focus of regional assessment and modeling by the Integrated Water Availability Assessments, Integrated Water Prediction, and other Water Resources Mission Area programs.

The 36 basins selected as finalists were the highest ranked among 163 basins considered, based on a numerical ranking approach that considered three major criteria:  natural hydrologic setting, anthropogenic stresses, and water-resource “importance.” The 36 basins represent the range in natural hydrologic settings for the conterminous U.S. and, within each region, are basins with high levels of water-resource stresses.

The next step in IWS Basin selection will be to obtain stakeholder input from within the USGS and from other Federal agencies, State and local environmental management agencies, and non-governmental organizations with interests in water resources. Final selection of IWS Basins will be made by Water Resources Mission Area management.

The Delaware River basin was selected in 2018, prior to the initiation of the basin ranking process, as a pilot basin for study by the Next Generation Water Observing Systems and the Integrated Water Availability Assessments programs, becoming the first of the 10 planned IWS Basins. Based on this ranking process and stakeholder input, the headwaters of Colorado and Gunnison Rivers was selected as the second IWS Basin in 2019.