Ventura County, California — public water systems

At a glance

95 active public water systems are filed under Ventura County, California in EPA's SDWIS records, together reporting 882,799 people served. The largest is Oxnard Water Dept, which reports serving 200,232 people. 68 are community water systems serving people where they live; the other 27 are non-community systems, such as schools, workplaces, campgrounds and gas stations with their own supply.

Dataset updated October 2026 . Source: EPA SDWIS/ECHO, refreshed quarterly.

Active systems

Population served

882.8K

Community systems

Groundwater share

54.7%

How does Ventura County compare with other California counties?

Ventura County has the 28th-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 882,799 people served in total, the 12th-largest county figure in the state and 2.1% of the statewide total. The average system here reports serving 9,293 people, about 63% above 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 Ventura County's drinking water come from?

By primary water source, Ventura County's active systems draw on groundwater (48, 51%), purchased surface water (37, 39%), surface water (6, 6.3%) and purchased groundwater (2, 2.1%). Overall, 55% rely mainly on groundwater (including purchased groundwater) and 45% 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, Oxnard Water Dept, draws primarily on purchased surface water.

What kinds of water systems operate in Ventura County?

Ventura County's active systems break down as 68 community systems (72%), 20 non-transient non-community systems (21%) and 7 transient non-community systems (7.4%). 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 (62%), local government (31%), federal government (6.3%) and state government (1.1%).

The 50 largest water systems in Ventura County

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Active public water systems in Ventura County, California
#	Water system	County	Population served	Type	Source
1	Oxnard Water Dept	Ventura	200,232	Community	Purchased surface water
2	Ventura Water Department	Ventura	113,500	Community	Surface water
3	Ventura Wwd No. 8 - Simi Valley	Ventura	94,738	Community	Purchased surface water
4	Cal American Water Co	Ventura	66,809	Community	Purchased surface water
5	City of Thousand Oaks Water Department	Ventura	53,157	Community	Purchased surface water
6	Camarillo Water Dept	Ventura	46,824	Community	Purchased surface water
7	Golden State Water Company - Simi Valley	Ventura	45,128	Community	Purchased surface water
8	Ventura Cwwd No. 1 - Moorpark	Ventura	35,514	Community	Purchased surface water
9	Camrosa Water District	Ventura	32,700	Community	Purchased surface water
10	City of Santa Paula	Ventura	31,018	Community	Groundwater
11	Port Hueneme City Water Dept	Ventura	21,407	Community	Purchased surface water
12	California Water Service Co - Westlake	Ventura	19,533	Community	Purchased surface water
13	Fillmore Water Dept	Ventura	16,419	Community	Groundwater
14	Triunfo Water & Sanitation District	Ventura	13,898	Community	Purchased surface water
15	Casitas Municipal Water Dist	Ventura	11,005	Community	Surface water
16	Naval Base Ventura County, Port Hueneme	Ventura	8,625	Community	Purchased surface water
17	Ojai Water System	Ventura	6,801	Community	Purchased surface water
18	Ventura River Water District	Ventura	6,100	Community	Purchased surface water
19	Naval Base Ventura County, Point Mugu	Ventura	5,700	Community	Purchased surface water
20	Pleasant Valley Mutual Water Co	Ventura	5,000	Community	Purchased surface water
21	Channel Islands Beach Csd	Ventura	4,560	Community	Purchased surface water
22	Meiners Oaks Cwd	Ventura	4,200	Community	Purchased surface water
23	Smith Forks Water System	Ventura	3,000	Transient non-community	Groundwater
24	Rio Mesa High School/Oxnard Uhs	Ventura	2,600	Non-transient non-community	Groundwater
25	Crestview Mutual Water Co	Ventura	2,079	Community	Purchased surface water
26	Cal American Wc - Las Posas Estates	Ventura	2,039	Community	Purchased surface water
27	Cal American Water Company - Piru	Ventura	2,003	Community	Groundwater
28	Ventura Cwwd No. 17 - Bell Canyon	Ventura	1,946	Community	Purchased surface water
29	Vineyard Avenue Acres Mwc	Ventura	1,820	Community	Groundwater
30	Ventura Cwwd No. 38 - Lake Sherwood	Ventura	1,759	Community	Purchased surface water
31	Cal American Wc - Rio Plaza	Ventura	1,709	Community	Groundwater
32	Ventura Cwwd No. 19 - Somis	Ventura	1,429	Community	Purchased surface water
33	Garden Acres Mutual Water Co	Ventura	1,335	Community	Groundwater
34	Vineyard Ave Estates Mwc	Ventura	1,200	Community	Purchased surface water
35	Limoneira Ranch #1	Ventura	1,187	Community	Purchased groundwater
36	Dempsey Road Mutual Water Co	Ventura	990	Community	Purchased surface water
37	Rio Manor Mutual Water Co	Ventura	983	Community	Groundwater
38	Nyeland Acres Mutual Water Co	Ventura	975	Community	Groundwater
39	Lake Piru Park - Uwcd	Ventura	960	Transient non-community	Surface water
40	Rio School Dist/Rio Del Valle School	Ventura	820	Non-transient non-community	Purchased surface water
41	Senior Canyon Mutual Water Co	Ventura	800	Community	Surface water
42	Cal American - Yerba Buena	Ventura	690	Community	Groundwater
43	Brandeis Bardin Institute	Ventura	665	Community	Purchased surface water
44	Glass House Camarillo Cultivation, LLC	Ventura	600	Non-transient non-community	Groundwater
45	Rancho Sespe Workers Imp Assoc	Ventura	600	Community	Groundwater
46	Rio School Dist/ Rio Real School	Ventura	550	Non-transient non-community	Purchased surface water
47	Usfs - Wheeler Gorge Campground	Ventura	500	Transient non-community	Groundwater
48	Thomas Aquinas College	Ventura	472	Non-transient non-community	Groundwater
49	Cloverdale Mutual Water Co.	Ventura	455	Community	Groundwater
50	Strickland Mutual Water Company	Ventura	429	Community	Groundwater

All other water systems in Ventura County (42)

The remaining active systems filed under Ventura County, largest first, with the population each reports serving.

Ventura County water systems: frequently asked questions

How many public water systems are in Ventura County, California?

EPA's SDWIS records file 95 active public water systems under Ventura County, California: 68 community systems (72%), 20 non-transient non-community systems (21%) and 7 transient non-community systems (7.4%).

Who supplies drinking water in Ventura County, CA?

The largest community water systems filed under Ventura County are Oxnard Water Dept (200,232 people served), Ventura Water Department (113,500 people served) and Ventura Wwd No. 8 - Simi Valley (94,738 people served). Which system serves a particular address depends on its service area, which EPA's SDWIS records do not include; a water bill or the local utility can confirm it.

Does Ventura County's drinking water come from groundwater or surface water?

Of the 95 active public water systems in Ventura County, 55% draw mainly on groundwater and 45% on surface water, counting purchased supplies. The largest system, Oxnard Water Dept, uses purchased surface water.

Where can I find a water quality report for Ventura County?

Each community water system must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1, covering the previous calendar year. 68 community systems are filed under Ventura County, so the report to look for is the one from the system that supplies your address.

How can I check violations for a water system in Ventura County?

Open the system's profile from the list on this page. Each profile shows the most recent Safe Drinking Water Act violations in EPA's records, with plain-English labels and whether each one is resolved. For current compliance status, EPA ECHO is the primary source.

More California water systems

About this data

Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.

Cite as: AquaCensus, “Public water systems in Ventura County, California”, https://aquacensus.com/water-systems/california/ventura (data as of October 1, 2026).