Groundwater is a critically important resource in Ventura County. Proper management of this limited resource is vital to meet the current and future demands of urban, industrial, agricultural and in-stream water uses. The Ventura County Groundwater Section addresses all water supply sources including groundwater, surface flows, imported and reclaimed water, as well as alternative resources such as conjunctive use and desalination. Water management programs include drought planning, governmental quality compliance, and several water conservation programs.
The Groundwater Section has been providing groundwater information (water well levels and water quality lab results) along with well construction data to the public for more than 45 years, and will continue to improve such service as much as possible. In addition, we conduct data gathering of both groundwater quality and groundwater levels by sampling and measuring existing water extraction wells and aquifer-specific monitoring wells on a routine basis. Such activities help us understand and track vital water resources to address any potential concerns before they become problems. New and existing information is recorded, coordinated, and included in topical studies.
Groundwater is just one piece of the larger water supply and demand picture, and the Groundwater Section has focused recently on integrating our information into regional Watershed Management Planning efforts. Working with other agencies and interests helps achieve our goals toward water quality protection and quantity improvement. Our data collection routines support consultant and public needs, statewide Department of Water Resources (DWR) data needs, and special studies or reports.
A variety of water quality issues affect Ventura County water resources. Quality issues include wastewater and package treatment plants, seawater intrusion, septic tanks, urban stormwater runoff, abandoned water wells, agricultural runoff, aggregate resource management and naturally occurring contaminants. All of our efforts and tasks add to a continuing a Countywide effort to maintain and improve the management and quality of water resources.
An aquifer is a layer of porous sand, gravel, silt or a mix of those in some combination that contains and transmits groundwater. When water can percolate from the surface down into the saturated zone, we call that an unconfined aquifer. This saturated layer is called the water table. Below the water table, all pore spaces are saturated with water. Any silty clay, tightly compressed silt, or non-porous deposits (like fractured bedrock) with low porosity that only permits limited transmission of groundwater is called an aquitard because it slows or retards the flow of groundwater. An aquiclude is a substrate with porosity that is so low it is virtually impermeable to groundwater. A confined aquifer is a sandy or porous layer with an impermeable layer of solid rock or hard clay above and below it. Groundwater in a confined aquifer is under pressure so when a well is drilled into it, the trapped groundwater can flow up the well casing. This can sometimes create an artesian well that will flow freely without the need for a pump.
The characteristics of aquifers vary with the underlying geology where they occur. Alluvial or stream-deposited materials that have accumulated as valley fill sediments create the best aquifers and are usually the most productive sources of groundwater. There are five such aquifers beneath the Oxnard Plain stacked like a layer cake with clay or shale layers separating them like the frosting between slabs of a stacked up sponge cake. The more wells (or straws as some people call them) there are that suck groundwater from these aquifer layers, the lower the pressure in each water-bearing zone. If too much groundwater is sucked out of a particular area, subsidence (aquifer collapse or sinking of the ground surface) can occur. This can cause roads to sink, bridges to collapse, buried pipelines to break, and other very costly problems.
The volume of groundwater in an aquifer can be estimated by measuring water levels in local wells and by examining geologic records from well-drilling to determine the extent, depth and thickness of water-bearing (aquifer) sediments. When wells are drilled, the depth to water is recorded and soil samples are collected for analyses. Pumping tests are also performed in each well to determine the flow characteristics of each aquifer or well location.
Groundwater makes up about twenty percent (20%) of the world’s freshwater supply, which only equals about 0.61% of the entire world’s water volume (includes all oceans and permanent ice). This makes groundwater an important resource that often serves as a natural storage tank available during times of drought. Unfortunately, we often rely too much on groundwater as our main supply during droughts that last longer than a couple of years, and this dependence on groundwater can lead to over-pumping and water shortages. Groundwater is naturally replenished by surface water from precipitation, streams, and rivers, however this recharge does not occur during drought periods. So groundwater can only be a short-term ‘reservoir‘ of fresh water.
Groundwater is withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is called Hydrogeology or Groundwater Hydrology. Groundwater is often cheaper, more convenient, and less vulnerable to pollution than surface water. Therefore, it is commonly used for public water supplies. California annually withdraws the largest amount of groundwater of all the states. Groundwater pollution most often results from improper disposal of wastes on land. Major sources include industrial and household chemicals and garbage landfills, excessive fertilizers and pesticides used in agriculture, industrial waste ponds, process wastewater from industrial manufacturing, oil field brine pits, leaking underground storage tanks or pipelines, sewage sludge, and septic systems.
Ventura County Groundwater Goals:
- To Protect and Enhance Existing Water Supplies, and
- To Conserve Existing Water Supplies for Current and Future Needs.
We do this by:
- Continuing to support all water conservation programs and encourage full implementation of best management practices (BMP’s) for urban, agriculture and industrial uses.
- Supporting the beneficial recycling of wastewater and appropriate water conservation measures while recognizing the extent to which some treated wastewater is already recycled following discharge.
- Protecting and Enhancing Existing Surface Water and Groundwater Supplies.
Water demand in Ventura County has nearly tripled over the last 25 years, and is expected to double again by 2050. Groundwater is the largest single source of water in Ventura County. It provides about 67% of the locally utilized water in the County. Agricultural demand accounts for 68% of the total demand for groundwater in the County. So it is vitally important that the Ventura County Groundwater Section maintain a due diligence over our limited underground and unseen water supplies.
Groundwater Resource Management:
Groundwater management agencies (like the local Fox Canyon Groundwater Management Agency or FCGMA), are tasked with calculating the safe or “sustainable yield” of Ventura County aquifers. The effects of groundwater overdraft may take decades to notice, and sometimes centuries to replace. Groundwater management and planning often mean calculating groundwater withdrawal limits, and issuing permits or assigning annual extraction allocations based on predicted effects several years or even decades into the future.
A couple of ways groundwater can be artificially recharged are worthy of brief mention. Diverting surface runoff from streams or rivers into “percolation” or “recharge ponds” has been demonstrated as one effective means by several water districts. Direct recharge via injection wells is another method – but often costly – and with limited success. More recently, flood mitigation schemes intended to protect infrastructure built on floodplains, have been proposed by diverting flood waters into agricultural fields or designated basins to recharge aquifers to utilize so-called natural flooding in a positive way.
Phone: (805) 654-2907
PLEASE NOTE: Requests for well seal inspection (for new wells or destruction of old wells) must be made at least 24 hours in advance.
More Information about Water Well Permits.
PLEASE NOTE: A new fee schedule took effect on July 1, 2015
Phone: (805) 654-5164
PLEASE NOTE: All new wells in the Fox Canyon Groundwater Management Agency boundary must first obtain a no-fee permit from the FCGMA prior to applying for a well construction permit from the County Watershed Protection District – Groundwater Section. Special requirements may also apply from the Santa Paula Basin Pumper’s Association, the Ojai Basin Groundwater Management Agency, and various cities within the county.
Water Level Or Water Quality Data:
Phone: (805) 654-2907
Well Log or Well Location Information:
Phone: (805) 654-2907
Water Supplier or Purveyor Information:
Phone: (805) 654-2907
Water Purveyors MAP: Inventory of Public and Private Water Purveyors in Ventura County:
(PDF, 2.67 Mb, 26″ Wide x 28″ High)
Phone: (805) 645-1321
- 2015 Groundwater Report
- 2014 Groundwater Report
- 2013 Groundwater Report
- 2012 Groundwater Report
- 2011 Groundwater Report
- 2010 Groundwater Report
- Basin Map (PDF, 678 KB)
Well Ordinance Information:
- Notice to Prospective Well Owners and Moratorium Area Map
- Exhibit No. 1: Policies and Procedures for Water Well Flowmeter Calibration
- Ventura County Well Ordinance No. 4468
- Ventura County Well Ordinance No. 4501
- Resolution 21-070
- Ventura County Fee Schedule on Letterhead
- Procedures for Locating a Well