Source Water Assessment Reports


Deep blue body of water with mountain ridge in the background.

Zone 7 Water Agency draws from a diverse portfolio of drinking water sources including local and imported surface water as well as groundwater which we pump from wells. We carefully monitor all these sources to ensure their continued quality and to protect the safety of our water supply.

A source water assessment is conducted on each groundwater well as required by the California State Water Resources Control Board, commonly referred to as the State Water Board. Sanitary surveys for surface water supplies are conducted every five years. The latest sanitary survey for the Delta and the State Water Project was completed in June 2017.

Protecting our source water is an important part of providing safe drinking water to the public that meets the stringent Zone 7 water quality targets. By monitoring for potential contaminants, we can proactively address threats to water quality. For example, groundwater sources can be vulnerable to releases from chemical/petroleum pipelines, leaking tanks, groundwater contamination plumes, septic tanks, and wastewater-collection systems.

Surface water can become contaminated as it travels through the Sacramento and San Joaquin watersheds and the Delta. After leaving the Delta, water is transported to Zone 7 via the South Bay Aqueduct (SBA). The SBA water quality can become polluted from local cattle grazing, wildlife activities and recreational activities in the watersheds of the Bethany and Del Valle reservoirs. In order to deliver the high-quality water we expect in Zone 7, we proactively participate in a number of activities to improve water supply reliability and the water quality of the SBA.

View Source Water Assessment Reports

Zone 7 drinking water sources include local and imported surface water as well as groundwater. A source water assessment is conducted on each drinking water source as required by the State Water Resources Control Board, Division of Drinking Water (DDW). The State Water Project’s Watershed Sanitary Survey is updated every five years, while assessments for Zone 7’s local wells and water treatment plant intakes on the South Bay Aqueduct are done on a one-time basis. Click on the links below for each applicable report:

Groundwater wells
Treatment Plant Intakes on South Bay Aqueduct
State Water Project

To view Zone 7’s annual Consumer Confidence Report, click here.