California Population Trends by Geography

The county‑DAU table uses DOF July county totals, while the county‑DAU‑places table uses DOF January place totals. DOF produces population estimates twice each year—January and July. January estimates are available at the level of census places within each county, whereas July estimates are produced at the county level.

As a result, county totals differ between the two due to six months of natural change (births, deaths, migration) and because January estimates incorporate preliminary vital statistics that are finalized in the July series. Throughout development, intermediate results were reviewed and adjusted as needed, applying professional judgment 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 is available for visualizing population trends by county and DAU and places. Please note that county-DAU-places values reflect DOF January estimates, while County-DAU values reflect DOF July estimates.