California Population Trends by Geography
This dataset provides population estimate trends from 1998 to the current year for each of California’s 58 counties, further disaggregated by Detailed Analysis Units (DAUs) - the smallest geographic units historically used by the California Department of Water Resources for water planning as part of the California Water Plan. DAUs are subdivisions of Planning Areas and often align with county boundaries, although a single DAU may span multiple counties. They have traditionally supported water demand estimates based on crop and land use types. The population estimates were developed using U.S. Bureau Census 2000, 2010 and 2020 data. Throughout the estimation process, intermediate results were reviewed and adjusted as needed, with professional judgment applied to smooth trends where appropriate. Since the California Water Plan is retiring DAUs as its planning and analysis framework, future updates to this dataset will transition away from DAU based geography. Instead, population estimates will be provided based on other geographic units, such as the 8-digit Hydrologic Units (HUC8) defined by the U.S. Geological Survey’s Watershed Boundary Dataset. A [dashboard](https://tableau.cnra.ca.gov/t/DWR_Planning/views/DAU-County-Pop-Trends_16297434958570/PopTrendsforaCountywithmap?%3Aembed=y&%3Aiid=1&%3AisGuestRedirectFromVizportal=y) is available for visualizing historical population trends by county and DAU.
Data files
| Data title and description | Access data | File details | Last updated |
|---|---|---|---|
County/DAU Population Trends Annual Data This dataset provides population estimate trends from 1998 to the current year for each of California’s 58 counties, further disaggregated by Detailed Analysis Units (DAUs) - the smallest geographic units historically used by the California Department of Water Resources for water planning as part of the California Water Plan. DAUs are subdivisions of Planning Areas and often align with county boundaries, although a single DAU may span multiple counties. They have traditionally supported water demand estimates based on crop and land use types. The population estimates were developed using U.S. Bureau Census 2000, 2010 and 2020 data. Throughout the estimation process, intermediate results were reviewed and adjusted as needed, with professional judgment applied to smooth trends where appropriate. Since the California Water Plan is retiring DAUs as its planning and analysis framework, future updates to this dataset will transition away from DAU based geography. Instead, population estimates will be provided based on other geographic units, such as the 8-digit Hydrologic Units (HUC8) defined by the U.S. Geological Survey’s Watershed Boundary Dataset. A [dashboard](https://tableau.cnra.ca.gov/t/DWR_Planning/views/DAU-County-Pop-Trends_16297434958570/PopTrendsforaCountywithmap?%3Aembed=y&%3Aiid=1&%3AisGuestRedirectFromVizportal=y) is available for visualizing historical population trends by county and DAU. | Download | CSV | 04/23/25 |
Supporting files
| Data title and description | Access data | File details | Last updated |
|---|---|---|---|
Dashboard of Population Trends by County and DAU The dashboard, created using Tableau, provides a graphical representation of population trends by county and DAU. | WEBSITE | 04/23/25 | |
DAU County Shapefile 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. | 04/23/25 |