The Carneros Watershed

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The Carneros Creek Watershed is located in Monterey County, on the central coast of California, contained within the Elkhorn Watershed. Carneros Creek, not to be confused with Carneros Creek of Napa County, is the main freshwater tributary to the Elkhorn Slough.

Picture of watersheds surrounding Elkhorn Slough. The Carneros Creek Watershed is contained within the Elkhorn Watershed and includes all areas upstream from Elkhorn Slough. Copied from Elkhorn Slough Foundation.

Location, Size and Climate

Located within Monterey and San Benito Counties, California, the Carneros Creek Watershed drains an area of 71.6 km² from the towns of Aromas, Las Lomas, and Prunedale. The area has a Mediterranean climate [1], characterized by hot dry summers and cold wet winters. Average annual precipitation for the area is 23.25 inches, with the majority of precipitation events occurring from November through March [2].

Environmental Concerns

Contained within the Elkhorn Watershed, the waters from the Carneros Creek Watershed flow into Elkhorn Slough and account for some of the potential watershed impacts on Elkhorn Slough. The Carneros Creek Watershed provides habitat to some species listed as threatened or endangered by the US Fish and Wildlife Service, such as the California Red-Legged Frog (Rana draytonii), California Tiger Salamander (Ambystoma californiense), and the Santa Cruz Long-Toed Salamander (Ambystoma macrodactylum croceum) [3]. Carneros Creek has been listed as impaired as defined under section 303(d) of the Clean Water Act[4]. Pollutants recognized under Carneros Creek's 303(d) listing includes:

  • Ammonia
  • Chlorophyll-a
  • Fecal Coliform
  • Low dissolved oxygen
  • Tubidity
  • pH

Land Use and Land Cover

Mixed land uses within the watershed include rural residential, livestock grazing, agriculture, and undeveloped/conservation areas. Agricultural operations utilize approximately 10% of the watershed primarily for growing strawberries. Other agricultural crops include, raspberries, flowers, vegetables, and fungi. [5]

Before settlement, it is believed that the watershed supported native grasslands, oak woodlands, maritime chaparral, and riparian areas. According to Largay [6], Carneros Creek fed numerous wetlands which were lost after channel control measures were implemented by settlers.

Surface Water and Groundwater Hydrology

Sometimes considered part of the Elkhorn Slough, Carneros creek is the only stream located within the Carneros Watershed, without any tributaries listed by USGS. Carneros Creek (Waterbody ID # CAR3060001020090115165216)[7] does not always appear in the maps and literature. Carneros is a seasonal stream; its flow depends on seasonal precipitation, leaving the creek dry during most summer and some winter months. It is this seasonal drying which enables seawater to travel upstream from the Elkhorn Slough flow into the creek during high tides [8].

According to the Department of Water Resources, there are at least two groundwater basins within the Carneros Watershed [9], however, as sited in Ferriz [10], the Carneros watershed is occupied by the lower sub-basin of the Salinas Valley Watershed, while according to the Pajaro Valley Water Management Agency [11], the lower reaches of the Carneros Watershed belong to the Pajaro Valley Groundwater Basin. More research needs to be done on this topic.

Available hydrological data

Location of Precipitation and Stream Gages in the Carneros Watershed

The Carneros Watershed has three flow gages within its watershed and several precipitation gages located in and around the watershed. These gages are managed and monitored by different organizations and agencies.

Precipitation Gages

Stream Gages

  • CSUMB at Johnson Road. Coordinates: 36.859882 N -121.707658
  • CSUMB at Sill Road. Coordinates: 36.861965 N -121.722738
  • USGS and DWR Pajaro. Coordinates: 36.902 N -121.605 W


A management plan for the Carneros Creek Watershed has been prepared by the Carneros Creek Association in 2000 to implement measures such as:

  • erosion control
  • sustainable flood management
  • water quality improvements
  • restoration of riparian corridors
  • and water conservation

Several local organizations, such as ALBA, the Elkhorn Slough Foundation, ESNERR, and Triple M Ranch, provide support, offer educational opportunities, and conduct research in The Carneros Watershed.

Restoration Activities

Multiple restoration projects are underway in the Carneros Watershed. Currently a wetland restoration project funded by the EPAs West Coast Estuary Initiative aims to restore 55 acres of floodplain surrounding Carneros Creek. This project began in July 2009 and is projected to end July 2013. Listed restoration-related activities in this project include:

  • non-native vegetation removal
  • native vegetation reintroduction
  • monitoring
  • adaptive management
  • education and training of land-use planners, land managers, farmers, and public [12]


  1. Holloway R. 2010. Annual Sediment Retention and Hydraulic Residence Time Variability in a Riverine Wetland Receiving Unregulated Inflow from Agricultural Runoff http:://
  2. The Weather Channel
  3. U.S. Fish & Wildlife Service Listed Species]
  4. State Water resources Board Integrated Report
  5. Largay B. 2007 ALBA Triple M Wetlands Restoration Project Existing Conditions and Conceptual Design
  6. Largay B. 2007 ALBA Triple M Wetlands Restoration Project Existing Conditions and Conceptual Design
  7. Final California 2010 Integrated Report( 303(d) List/305(b) Report)
  8. Pajaro Valley Water Management Agency
  9. California Department of Water Resources
  10. Ferriz H. 2001. Groundwater Resources in Northern California
  11. Pajaro Valley Water Management Agency
  12. Targeted Watershed Grants Program



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