Source Water Protection


Protecting water at the source, mainly reserviors and associated intakes, is important for water quality and water supply reliability.  

Potential Risk

Reserviors and associated intakes are susceptible to potential contamination from land use practices, such as agricultural and urban runoff, recreational activities, livestock grazing, and residential and industrial development. Imported water sources are also at risk from wastewater treatment plant discharges, seawater intrusion, and wildfires in open space areas. In addition, local sources are  vulnerable to potential contamination from commercial stables and historic mining practices.

Pollutants include MTBE, excess nitrates, mercury, perchlorates and other contaminants. Monitoring water quality and preventing or removing contaminants effectively are key components of source water protection.  


Protecting source water safeguard public health, help reduce costs and allow the District and city planning departments make well-informed land use decisions.
Safeguard Public Health- Source water protection offers the first line of defense against potentially harmful pollutants by stopping contaminants at the source. Such efforts greatly reduce public health risks.

Reduce Costs- Keeping pollutants out of the water supply costs less than removing them at water treatment plants.  Therefore, source water protection programs provide a more economical solution to cleaning contaminated source water supplies.

Provide Information for Planning Purposes- District managers and local planning agencies can take advantage of source water assessments to develop effective emergency response plans, water infrastructure reliability plans, and municipal land use and development planning and zoning efforts. 


Both the Federal Environmental Protection Agency and the California Department of Health Services require Source Water Assessments and Watershed Sanitary Surveys. These assessments examine possible sources of contamination, identifies vulnerabilities and prioritize activities needed to protect source water.

The steps involved in assessing source water include: 

Delineation- defines source water protection zones.

Inventory- an inventory of the Possible Contaminating Activities (PCAs) within the source protection zones.

Vulnerability Analysis- identifies the potential sources of contamination. This information is used to alert the public water system to the contaminant sources that have the greatest likelihood of affecting the water supply.

Reporting- Assessment reports include maps of the source water area, lists of potential sources of contamination, and summaries of the vulnerability analyses.

Protecting Our Water

The District works to protect, enhance, and restore surface water quality in the County's drinking water supply reservoirs. Source Water Protection Zones created by the District include substantial protective buffer zones around reservoirs, source water intakes and creeks supplying drinking water. District managers use information from Source Water Assessment reports to identify and prioritize protection activities for local and imported water supplies. The District collaborates with state and local agencies and the community to determine appropriate source water protection measures to prevent surface water contamination.


Watershed Management Program

The Watershed Management Program is a jointly administered program that provides heightened awareness in the local community about watershed protection and Best Management Practices (BMPs) through education. The Watershed Management Program also protects local drinking water from contaminant sources, and raises awareness about watershed management and protection of water resources in the local area.


Septic Systems and Waste Disposal Facilities

The District evaluates septic systems and waste disposal facilities. When problems are identified, the District works with the Department of Environmental Health and the homeowners to resolve the problem.


Livestock and Manure Handling Areas

The District works with the County Parks and Recreation Department and individual horse stable operators to reduce contaminated storm water runoff from livestock and manure handling areas.


Recreational Activities

In collaboration with the County Parks and Recreation Department, the community, and recreational boaters, the District works to ensure that no contamination events occur from recreational activities on or near the reservoirs. The strategy includes water quality monitoring, and managing the number and type of watercraft allowed on the reservoirs.


Regulations/Land Use Policies

The District partners with cities to integrate source water protection in municipal permit requirements, guidelines and standards, zoning, and land use regulations for community projects and activities in reservoir watersheds.

The District works to prevent and reduce pollution to streams, including developing stormwater protection and pollution prevention plans. The District participates with 14 other agencies in the Santa Clara Valley Urban Runoff Pollution Prevention Program to implement pollution prevention measures, monitoring, and public education and outreach.


Land Preservation

The District’s land preservation projects aim to protect the county’s streams through purchasing land, development rights or conservation easements for habitat enhancement, mitigation, and water quality. The project operates in partnership with property owners, parks and open space districts, land trusts and conservation organizations.


Incident Response/Pollution Prevention Hotline

A 24-hour Incident Response/Pollution Prevention hotline facilitates emergency response planning and reporting of spills and illicit discharges. The Hotline number, 1-888-510-5151, is used for reporting incidents of illegal dumping of trash, debris and hazardous materials in water ways.


Creek Cleanup

District maintenance crews provide routine creek cleanup for trash, debris, and sediment that accumulate in district waterways. In addition, the district's Adopt-A-Creek Program coordinates volunteers to organize stream clean-up days.


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