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Res-Indoor Budget: SDWIS Residential Population

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Published by:
California State Water Resources Control Board
Last updated:
November 24, 2025
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Consistent with Health and Safety Code section 116530 and California Code of Regulations title 22 §64412, public water systems report the population served during a specified reporting period and the population type, which can be reported as either Residential (R), Non-Transient (N), Transient (T), or Wholesale (W). This table contains residential (R) population data for public water systems owned and operated by urban retail water suppliers. ["Residential"](https://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/documents/ear/ear-help-tips.pdf) refers to the number of persons who reside within the water system service area for more than half of the year. For each system, the R-population value represents the most recently reported and most contemporary value for the prior state fiscal year (July to June), as denoted in the FY_START_DATE and FY_END_DATE columns. Public Water System data, including population, can be viewed using [Drinking Water Watch](https://sdwis.waterboards.ca.gov/PDWW/). If the population values identified in this dataset need to be revised, please contact the appropriate State Water Resources Control Board’s Division of Drinking Water [district office](https://www.waterboards.ca.gov/drinking_water/programs/documents/ddwem/DDWdistrictofficesmap.pdf) and update accordingly. The Division of Drinking Water has documented the procedure to request population changes outside of the Electronic Annual Report [here](https://data.ca.gov/dataset/c69ac02b-adfb-459a-bc58-bf69a8b572d2/resource/0ba8a039-9459-4796-916d-179cf0da6173/download/guidance_changing-population-procedure.pdf).

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