River basins or hydrologic units are often the spatial unit used for aggregating and analyzing components of the water cycle such as precipitation, runoff, riverine discharge, etc. The hydroSHEDS dataset, derived from the Shuttle Radar Topography Mission, are the most commonly used global hydrologic unit for these analyses. But when planning water use or gaps, political boundaries need to be considered. Water provinces (Straatsma et al 2020) provide a much more realistic hydrologic unit for such purposes.

Esri’s World Administration Divisions (2011) defines 3,300 subnational units. Areas less than 150,000 sq km were aggregated into 1,099 regions. The water provinces were then calculated by overlaying these regions with the major basins from hydroSHEDS.  After sliver polygons were removed, the result was 1,604 unique units based on river basins but constrained by political boundaries. These water provinces provide a suitable unit for longterm water use planning, especially at local scales.