Water Quality Monitoring

DWR has conducted water quality monitoring for the California State Water Project since 1968. This program is currently managed by the Division of Operations and Maintenance,  Environmental Assessment Branch. Initially, this program sought to monitor eutrophication (an increase in chemical nutrients) and salinity in the SWP. Over time, the water quality program expanded to include parameters of concern for drinking water, recreation, and wildlife.

Water quality samples collected for this program include chemical, physical, and biological parameters, collected at regular intervals throughout the year. The coverage of this program includes more than 40 locations associated with the SWP, from the Feather River drainage in the north to Lake Perris in the south. Samples at these locations are either collected by discrete grab samples or monitored by automated stations.

The goal of the water quality monitoring program is to provide accurate, reliable data to support:

  • Understanding spatial and temporal changes in SWP water quality.
  • The planning of future raw water and/or drinking water treatments.
  • Identifying and responding to toxic substance spills, floods, and other water quality emergencies.
  • Determining SWP water quality compatibility with California drinking water standards, contractual requirements with the State Water Contractors, or other criteria.


2024 Aquatic Herbicide and Algaecide Applications in the SWP

DWR's O&M will be applying herbicides and algaecides to several facilities throughout the State Water Project in 2024. Treatments will occur on an as-needed basis to control algae and aquatic weeds. The herbicides to be used may include copper, endothall, and/or diquat based compounds. Locations to be treated include, but are not limited to, the South Bay Aqueduct, Dyer Reservoir, Patterson Reservoir, Clifton Court Forebay, O'Neill Forebay, the California Aqueduct, the Coastal Branch Aqueduct, Pyramid Lake, Castaic Lake, East Branch Aqueduct, Silverwood Lake, Perris Lake, Quail Lake, Thermalito facilities, and Los Banos Reservoir. Public access to SWP waterbodies will be restricted during aquatic herbicide treatments. For questions email Tanya Veldhuizen, tanya.veldhuizen@water.ca.gov.