Key Characteristics

The Uvas-Llagas Watershed is a 104-square-mile region which is distinguished by its agricultural lands and natural areas.  Uvas-Llagas is part of the larger Pajaro River Watershed which covers portions of Santa Cruz, Monterey, San Benito and Santa Clara Counties.

Key characteristics of the Uvas-Llagas Watershed:

  • 50% of water use in the Uvas-Llagas is for agricultural purposes.
  • The creeks in the Uvas-Llagas are the only waterways in Santa Clara County that flow southward.
  • Trails and open space in the watershed include the 20-acre San Pedro Ponds walking trail and Uvas Canyon County Park.
  • Major water resource management issues in South County include:
    • Water supply reliability
    • Perchlorate in groundwater
    • Nitrates in both surface and groundwater
    • Llagas Creek flood protection
    • Protection and enhancement of steelhead habitat

Potential Partners and Collaborators

The District collaborates closely with other jurisdictions, agencies and stakeholders in and around the watershed to create healthy, livable environments. This collaboration is aimed at preserving and protecting the watershed through effective land use policies and programs. The South County Watersheds, also known as Uvas-Llagas Watersheds, are carefully managed through significant coordination with local stakeholders and landowners.

The District coordinates with a number of key federal and state agencies in regulating and managing this watershed, including: Army Corp of Engineers; Bureau of Reclamation, Environmental Protection Agency; Federal Emergency Management Agency; Department of Water Resources; Department of Agriculture; National Resource Conservation Service; Federal Fish and Wildlife Service, National Marine Fisheries Services; California Parks and Recreation; State Lands Commission, State Water Resources Control Board; and California Fish and Game.

On the regional level, the District collaborates with agencies to ensure that projects and programs in the watershed are consistent with county-wide goals. Key partners include: Midpeninsula Regional Open Space District; Regional Water Quality Control Board; South County Regional Wastewater Authority; Santa Clara Valley Audubon Society; and the Santa Clara Basin Watershed Management Initiative and its subgroups, notably the Coyote Watershed Workgroup and the Flood Management Subgroup. In addition, the District coordinates with other regional efforts such as the South Bay Water Recycling Program, Habitat Conservation Plan, the Santa Clara Valley Urban Runoff Pollution Protection Program (SCVURPPP), the Fisheries and Aquatic Habitat Collaborative Effort (FAHCE), the Santa Clara County Open Space Authority (SCCOSA) and the Santa Clara Valley Habitat Conservation Plan.

Portions of San Jose and Morgan Hill and all of Milipitas are located in the watershed, as well as portions Santa Clara County. Each jurisdiction’s general plan, zoning ordinance and other guiding documents establish their approach to infrastructure, flood protection, water quality, water supply, open space and recreation. The District works with each jurisdiction to ensure that overall programs and policies are compatible, effective and achievable.

In addition, the District also partners with various community groups to conduct stewardship activities in various creeks in the watershed. For example, South County Property Management, South Valley Disposal and Recycling, Malo Court Homeowners Association and the Morgan Hill Police Department  have adopted parts of Llagas Creek. Similarly, the Gilroy High School Interact Club, Sunnyslope School and Cub Scout Pack #770 have adopted parts of Uvas Creek. The District will continue to promote ongoing joint community partnership and advocacy opportunities.


Watershed Maps

The interactive map below shows the location of the Uvas-Llagas Creek watershed and illustrates some of the area's key features, such as major creeks, flood zones and groundwater basins.

To view key features, choose a layer from the "Select a layer to display" menu on the map below. You can select multiple layers to view at one time. Individual layers contain specific data that you can access by clicking on the layer itself.



Location and Natural Settings

Together, the Uvas Watershed and Llagas Watershed are commonly referred to as the South County Watersheds. Combined they drain a 104 square mile portion of the larger Pajaro River Watershed. The 1,300 square mile Pajaro River Watershed encompasses portions of four counties: Santa Clara, Santa Cruz, San Benito and Monterey. The Pajaro River Watershed extends from the Santa Cruz Mountains on the west to the Diablo Mountain Range on the east. The South County Watersheds occupy the western portion of the larger watershed.

The South County is largely comprised of agricultural and rural residential uses. Gilroy and Morgan Hill serve as the main urban centers, although the majority of the area is expected to remain in agriculture.


Key Water Resources Features

Water Supply

Approximately one-half of water use in the South County Watershed is devoted to the agricultural industry. This industry demand as well as projected urban water demand increases, is likely to result in water supply shortages. To address the potential deficit, the District is collaborating with local stakeholders, other agencies, cities and the County toward additional water conservation management.



There are two reservoirs in the South County, Chesbro and Uvas. The District maintains and operates both reservoirs with the main purpose of capturing runoff from winter storms. The Chesbro Reservoir was completed in 1955 with the construction of the Chesbro Dam approximately three miles west of Morgan Hill. The reservoir has an average surface area of 283 acres, a capacity of 7,945 acre-feet.

In 1957, the Uvas Dam was completed, creating the Uvas Reservoir about two miles south of the Watsonville/Uvas Roads intersection. The reservoir has an average surface area of 288 acres, a capacity of 9,835 acre-feet.

Based on reservoir management practices, the District developed a series of rules to administer reservoir capacity and use. These rules take into account the various functions of the reservoir and include water temperatures needs, flood water storage needs, fish stream flow needs and minimum stream depth needs.


Major Creeks and Other Sources

While Uvas and Llagas are the major creeks in the watershed, other tributaries include Jones Creek, Crews Creek, Sargent Creek, Pacheco Creek, Gavilan Creek and sections of the Pajaro River.



The Santa Clara Valley Groundwater Basin consists of three subbasins: The Santa Clara Valley Subbasin in North County and the Coyote and Llagas Subbasins in South County. Groundwater recharge occurs through rainfall, stream flow seepage, and percolation of irrigation water, among other natural and artificial means.

The District operates several stretches of active in-stream recharge and four sets of recharge ponds to balance groundwater extraction and ensure groundwater sustainability in the South County Watershed.


Watershed Health

In managing watershed health, a balance must be found between the needs of habitat protection, water supply, flood management and ecosystem restoration and the needs for housing, economic development and recreation.




The South County Watersheds have a significant history of flooding, including in: 1937, 1955, 1958, 1962, 1963, 1969, 1982, 1986, 1996, 1997, 1998 and 2002. To increase 100-year flood conveyance capacity, the District initiated a number of flood control efforts. The Upper Llagas Creek Flood Protection Project is intended to improve channel stabilization, reduce erosion and sedimentation, improve water quality and to enhance fish and wildlife habitat. The Lower Llagas Creek Flood Protection Project focuses on increasing the capacity of the levee network. 


Water Quality

The Central Coast Regional Water Quality Control Board's analysis of Total Maximum Daily Loads (TMDL) determined that the South County Watershed is impaired for nitrate and perchlorate. The most common source of nitrate loading is fertilizer. The source of perchlorate is believed to be a former manufacturing facility. A number of farmers and ranchers have developed various methods to help reduce polluted runoff, contained in the Farm and Range Water Quality Plans.




Environmental Stewardship


Riparian Habitat

The majority of land in the undeveloped South County Watershed valley and floodplain is devoted to agriculture. Consequently, habitat restoration efforts will largely be on or near farm operations. Partnering with various agencies and stakeholders, the District is committed to implementing strategies and recommendations in the Santa Clara Valley Habitat Conservation Plan. This Plan seeks to establish long-term habitat protection and biodiversity in the South County watersheds. The Uvas and Llagas Creeks provide support to various habitats and species of special status, including the California tiger salamander.


Aquatic Habitat

Uvas Creek provides aquatic habitat for potential spawning and rearing for Steelhead, except under conditions of extreme drought. Llagas Creek has much less adequate habitat and spawning and rearing is less frequent and less extensive.




Browse the Framework

Related Plan Elements

District Has Primary Jurisdiction
E- Maintain the design floodwater conveyance capacities within District-owned channels. (P)
District Advocates
E- Support and promote land use decisions to maintain stream capacity. (T)
District Collaborates
E- Assist municipalities and citizens when needed to lessen potential flood impacts. (C)
District Collaborates
E- Include municipal planners in regional or local flood management planning activities. (C)
District Collaborates
E- Ensure floodplain maps (alluvial and tidal) are based on best available data. (C)
District Has Primary Jurisdiction
E- Balance the protection and restoration of sensitive fisheries and aquatic species, such as steelhead trout, with a reliable water supply. (P)
District Collaborates
E- Implement stream stewardship opportunities in capital and maintenance activities, including stream rehabilitation and environmental enhancements and seek to achieve the physical stability and ecological health of streams. (P and C)
District Collaborates
E- Engage in habitat conservation planning.(P and C)
District Has Primary Jurisdiction
E- Protect groundwater recharge areas in creeks and riparian corridors. (P)
District Has Primary Jurisdiction
E- Protect and preserve groundwater recharge areas.(P)
District Has Primary Jurisdiction
E- Improve water quality of listed impaired water bodies.(P and C)
District Collaborates
E- Promote the protection and preservation of water quality and providing stream stewardship. (C)
District Advocates
E- Promote the protection and preservation of sensitive groundwater recharge areas. (T)
District Collaborates
E- Reduce pollutants in streams from urban runoff and minimize the effects on surface and ground water.