Santa Clara River Valley – Oxnard
Statistics
- Basin Name
- Santa Clara River Valley – Oxnard
- Basin Number
- 4-004.02
- SGMA Basin Priority
- High
- Critically Overdrafted
- Yes
- Hydrologic Region Name
- South Coast
- Counties
- Ventura
Basin Notes
2003: Bulletin 118 basin description
2014: CASGEM Basin Prioritization: High
2016: Basin boundary boundary modification accepted with the Las Posas and Pleasant Valley subbasins
Revised basin boundary description
2019: Basin boundary modification per DWR: “revises and aligns the shared boundary between the Mound and Santa Paula subbasins to align with the Santa Paula adjudicated boundary. The modification also revises the shared boundary between the Oxnard, Mound, and Santa Paula subbasins to align with the Fox Canyon Groundwater Management Agency’s boundary and the Santa Paula adjudication boundary, where applicable. The scientific modification along the northern boundary of the Mound subbasin follows mapped alluvial units using a more detailed, 1:24,000 scale, qualified map.” Priority status remains high and critically overdrafted. Basin prioritization comments –
- Groundwater levels: CRITICAL OVERDRAFT 2016 Source: DWR 1) CASGEM/WDL/GWIDS: Longterm hydrographs show groundwater level decline. Source: DWR 2) There is evidence for the occerrence of long-term overdraft in at least two of the groundwater basins of the District. Groundwater levels have generally been declining for periods of several decades in the Oxnard Plain and Pleasant Valley basins. While the factors causing declining groundwater trends may have varied among these two basins, long-term replenishment rates have not kept up with long-term withdrawal rates in either of them. Thus, these basins are considered by the District to be in a condition of long-term overdraft. – Annual Investigation and Report of Groundwater Conditions within United Water Conservation District, March 2016
- Salt intrusion: Although groundwater levels in the Oxnard Plain area (Mound, Oxnard, Santa Paula, Pleasant Valley, & Las Posas Valley) have been relatively stable or have shown an increasing trend, in the coastal regions this stability is largely due to seawater intrusion and results in water of unusable quality replacing high quality groundwater. Rising groundwater levels in the Las Posas Valley are a result of active management to increase groundwater recharge beneath the Arroyo Las Posas. Seawater intrusion began in the Oxnard Plain area by 1930s and was widespread as early as the 1940s. Changes in groundwater management, including pumping reductions, shifting of pumping locations, construction of the Freeman Diversion, and the operation of the Pumping Trough and Pleasant Valley pipeline systems have significantly reduced seawater intrusion, but seawater intrusion conditions persist. Source: CentralCoastGWReport-Aug2014.pdf 2) Water purveyors in the Piru, Fillmore, Santa Paula, Mound, and Oxnard subbasins include United Water Conservation District and Ventura County. United Water Conservation District operates surface water facilities to encourage groundwater protection through conjunctive use (UWCD 2012). Groundwater issues within the United Water Conservation District service area (which includes all of the basin) include overdraft conditions, sea water intrusion, and high nitrate concentrations. Source: Final Long Term Operations EIS, U.S. Bureau of Reclamation, Chapter 7
- Subsidence: Water-level declines in the basin have induced land subsidence that was first measured in 1939 and have resulted in as much as 2.7 feet land subsidence in the southern part of the Oxnard Plain. The model simulated a total of 3 feet of land subsidence in the southern part of the Oxnard Plain and as much as 5 feet in the Las Posas Valley subbasins. Model simulations indicate that most of the land subsidence occurred after the drought of the late 1920s and during the agricultural expansion of the 1950s and 1960s. The results also indicate that subsidence occurred primarily in the upper-aquifer system prior to 1959, but in the lower-aquifer system between 1959-93 owing to an increase in pumpage from the lower-aquifer system. “groundwater and oil and gas production are probably major causes in the Oxnard Plain subbasin, and tectonic activity is probably a minor cause (Hanson et al., 2003)” Source: U.S. Geological Survey (USGS); Michelle Sneed provided information for two continuous GPS stations (VNCO and P729), but neither are in the Oxnard subbasin. Source: UNAVCO
2020: January 13, 2020 – Groundwater Sustainability Plan submitted to DWR by the Fox Canyon Groundwater Management Agency
2021: November 18 — GSP approved by DWR
At-A-Glance
California Water Library Documents About This Basin
Establishing ecological thresholds and targets for groundwater management
Nature Portfolio (Springer Nature) | April 3rd, 2024
Groundwater is critical for many ecosystems, yet groundwater requirements for dependent ecosystems are rarely accounted for during water and conservation planning. Here w
LandFlex Program’s Guidelines
California Department of Water Resources (DWR) | December 8th, 2022
LandFlex is a program that will provide $25 million in block grants to local government agencies to grant to farmers who limit agricultural water use. Local government ag
Statement of Findings regarding the Approval of the Oxnard Subbasin Groundwater Sustainability Plan
California Department of Water Resources (DWR) | November 18th, 2021
Relative risk of groundwater-quality degradation near California (USA) oil fields estimated from 3H, 14C, and 4He
Applied Geochemistry (Elsevier) | June 5th, 2021
Relative risks of groundwater-quality degradation near selected California oil fields are estimated by examining spatial and temporal patterns in chemical and isotopic
Groundwater Sustainability Plan for the Oxnard Subbasin
Fox Canyon Groundwater Management Agency (FCGMA) | December 13th, 2019
The Fox Canyon Groundwater Management Agency (FCGMA, or the Agency) has developed this Groundwater Sustainability Plan (GSP) for the Oxnard Subbasin (Subbasin; DWR Basin
Groundwater Sustainability Plan for the Pleasant Valley Basin
Fox Canyon Groundwater Management Agency (FCGMA) | December 13th, 2019
The Fox Canyon Groundwater Management Agency (FCGMA, or the Agency) has developed this Groundwater Sustainability Plan (GSP) for the Pleasant Valley Basin (PVB; DWR Basi
Status and Understanding of Groundwater Quality in the Santa Clara River Valley, 2007: California GAMA Priority Basin Project
U.S. Geological Survey (USGS) | September 26th, 2011
Groundwater quality in the approximately 460-square-mile Santa Clara River Valley study unit was investigated from April through June 2007 as part of the Priority Basin P
The Green Visions Plan for 21st Century Southern California: 21. Hydrology and Water Quality Modeling of the Calleguas Creek Watershed
University of Southern California (USC) | November 2nd, 2009
The hydrology and water quality simulation presented in this report is a part of the Green Visions Plan for 21st Century Southern California project. The primary
Simulation of Ground-Water/Surface-Water Flow in the Santa Clara–Calleguas Ground-Water Basin, Ventura County, California
U.S. Geological Survey (USGS) | July 15th, 2003
Ground-water is the main source of water in the Santa Clara–Calleguas ground-water basin that covers about 310 square miles in Ventura County, California. A steady incr
Bulletin No. 122, Ventura County and Upper Santa Clara River Drainage Area Land and Water Use Survey, 1961
California Department of Water Resources (DWR) | April 1st, 1965
Water Supply Conditions in Southern California during 1958-1959, Volume II, Water Level Data, Central Coastal and Los Angeles Regions
California Department of Water Resources (DWR) | May 1st, 1961
Bulletin No. 39-58, Water Supply Conditions in Southern California during 1957-1958, Volume II, Precipitation and Water Level Data, Central Coastal and Los Angeles Regions
California Department of Water Resources (DWR) | August 1st, 1960
Bulletin No. 39-57, Water Supply Conditions in Southern California during 1956-1957, Volume II, Precipitation and Water Level Data Central Coastal and Los Angeles Regions
California Department of Water Resources (DWR) | June 16th, 1958
Bulletin No. 39-57 Volume I Bulletin No. 39-57 Volume III Bulletin No. 39-57 Volume IV
Bulletin No. 39-W, Southern California Area Investigation, Ground Water Levels and Precipitation Records in Los Angeles, San Gabriel and Santa Ana River Basins and Antelope Valley and Water Supply Summary for Southern Portion of California 1954
California Department of Water Resources (DWR) | June 1st, 1956