Sonoma County, California — public water systems

How does Sonoma County compare with other California counties?

Sonoma County has the most active public water systems among the 201 counties listed for active California systems in EPA records; among the 72 with 3 or more systems, the median has 73. Its systems report 481,435 people served in total, the 18th-largest county figure in the state and 1.1% of the statewide total. The average system here reports serving 1,092 people, well below the California average of 5,706. Population figures are what each system reports; people served by more than one system, such as a wholesaler and the town that buys from it, are counted by each.

Where does Sonoma County's drinking water come from?

By primary water source, Sonoma County's active systems draw on groundwater (401, 91%), groundwater under influence of surface water (20, 4.5%), surface water (13, 2.9%) and purchased groundwater (5, 1.1%). Overall, 97% rely mainly on groundwater (including purchased groundwater) and 3.4% on surface water, compared with 85% and 15% across California. Groundwater means the system draws its water from wells or springs fed by underground aquifers. The county's largest system, City of Santa Rosa, draws primarily on groundwater.

What kinds of water systems operate in Sonoma County?

Sonoma County's active systems break down as 130 community systems (29%), 105 non-transient non-community systems (24%) and 206 transient non-community systems (47%). A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. A non-transient non-community water system regularly serves at least 25 of the same people for more than six months a year, but not where they live. Schools, factories, office buildings and hospitals with their own supply are typical examples. A transient non-community water system serves places where people do not stay long, such as gas stations and campgrounds, and regularly serves at least 25 people a day for at least 60 days a year. EPA lists their owner types as private (84%), local government (13%), state government (2.3%) and federal government (0.5%).