DWR subdivided California into study areas for planning purposes. The largest study areas are the ten hydrologic regions (HR), corresponding to the State’s major drainage basins. The next levels of delineation are the Planning Areas (PA), which in turn are composed of multiple detailed analysis units (DAU). The DAUs are often split by county boundaries, so are the smallest study areas used by DWR. The DAU/counties are used for estimating water demand by agricultural crops and other surfaces for water resources planning. Under current guidelines, each DAU/County has multiple crop and land-use categories. Many planning studies begin at the DAU or PA level, and the results are aggregated into hydrologic regions for presentation. This is considered a legacy dataset and will no longer be updated. After decades of use, Detailed Analysis Units are being retired as the framework dataset for the California Water Plan. Future updates of the California Water Plan will use the 8-digit Hydrologic Units of the U.S. Geological Survey’s Watershed Boundary Dataset as the planning and analysis framework. For more information on the Watershed Boundary Dataset, please visit https://data.cnra.ca.gov/dataset/watershed-boundary-dataset-wbd or contact nhd_stewardship@water.ca.gov. Questions about the California Water Plan may be directed to cwpcom@water.ca.gov.