Water Quality in California

Public Policy Institute of California (PPIC) | February 23rd, 2026

Water Quality in the State Water Project, 2000 and 2001

California Department of Water Resources (DWR) | April 1st, 2004

Water quality is routinely monitored at about 30 stations throughout the State Water Project (SWP). Water quality samples are collected by staff of the five field divisio

Water quality is routinely monitored at about 30 stations throughout the State Water Project (SWP). Water quality samples are collected by staff of the five field divisions in the Division of Operations and Maintenance and sent to Bryte Laboratory for analysis. SWP stations include those located in the Feather River watershed, North Bay Aqueduct, South Bay Aqueduct, and the California Aqueduct with its four terminus lakes in Southern California (Figure 1-1). Samples are collected on the third Wednesday of each month at the regular stations. Analyses include minerals, metals, metalloids, nutrients, organic chemicals, and disinfection by-product precursors. Further, around 15 automated water quality stations continuously monitor parameters such as salinity and turbidity on a real-time basis. Station descriptions and water quality constituents analyzed are detailed in Appendix A. Monitoring in the SWP is done on a routine basis to identify trends and assess water quality conditions with respect to long-term trends, operations, hydrology, seasons, emergencies, water treatment issues, and drinking water standards. Primary and secondary Maximum Contaminant Levels (MCLs) apply to drinking water and were compared to SWP data to provide a relative indication of raw water quality. MCLs are presented in Appendix B. Water quality trend assessment focused on salinity, bromide, and organic carbon. Water quality in the California and South Bay Aqueducts was good during 2000 due, in part, to above normal water year conditions in the Sacramento and San Joaquin Valleys. Drier conditions in 2001 resulted in less favorable water quality with respect to mineralogy. North Bay Aqueduct exports exhibited the usual impairments during winter as a result of organic carbon and turbidity increases. Water quality in the Feather River watershed was excellent, as usual, with low to non-detectable levels of minerals and minor elements.

Water quality measurements in San Francisco Bay by the U.S. Geological Survey, 1969–2015

Nature Portfolio (Springer Nature) | August 8th, 2017

The U.S. Geological Survey (USGS) maintains a place-based research program in San Francisco Bay (USA) that began in 1969 and continues, providing one of the longest reco

The U.S. Geological Survey (USGS) maintains a place-based research program in San Francisco Bay (USA) that began in 1969 and continues, providing one of the longest records of water-quality measurements in a North American estuary. Constituents include salinity, temperature, light extinction coefficient, and concentrations of chlorophyll-a, dissolved oxygen, suspended particulate matter, nitrate, nitrite, ammonium, silicate, and phosphate. We describe the sampling program, analytical methods, structure of the data record, and how to access all measurements made from 1969 through 2015. We provide a summary of how these data have been used by USGS and other researchers to deepen understanding of how estuaries are structured and function differently from the river and ocean ecosystems they bridge.

Water Quality of Groundwater Used for Public Supply in Principal Aquifers of the Western United States

U.S. Geological Survey (USGS) | September 8th, 2020

Water Quality Science in the Sacramento-San Joaquin Delta: Chemical Contaminants and Nutrients

Delta Stewardship Council (Delta Council) | July 26th, 2018

This review focuses on contaminants and nutrients in the Sacramento-San Joaquin Delta (the Delta), and on how findings about them have been sometimes used and sometimes n

This review focuses on contaminants and nutrients in the Sacramento-San Joaquin Delta (the Delta), and on how findings about them have been sometimes used and sometimes neglected in decisions related to ecosystem health in the Delta. The review considers water quality measurements made both in support of basic research and as part of routine monitoring studies in the Delta. However, the topic of monitoring per se is not comprehensively covered in this review because the Delta ISB is in the initial stages of reviewing the extensive monitoring enterprise in the Delta. This review of water quality is based on responses to a questionnaire sent to government agencies and science programs, interviews with water quality specialists and users of water quality data, relevant scientific publications, presentations observed in workshops and conferences, and public comments received on draft versions of the review. While we sought input from a broad range of stakeholders, we do not assume that we received a complete range of perceptions about this important issue. Additionally, water quality research and monitoring efforts are constantly evolving in the Delta, and several new programs and improvements were made as this review was being researched and prepared. This review should be considered to be part of an ongoing process by the Delta ISB.

Water Right Decision 1485: Sacramento-San Joaquin Delta and Suisun Marsh

California State Water Resources Control Board (SWRCB) | August 16th, 1978

Water storage decisions will determine the distribution and persistence of imperiled river fishes

Ecological Society of America (Wiley) | December 17th, 2020

Managing the world’s freshwater supply to meet societal and environmental needs in a changing climate is one of the biggest challenges for the 21st century. Dams provid

Managing the world’s freshwater supply to meet societal and environmental needs in a changing climate is one of the biggest challenges for the 21st century. Dams provide water security; however, the allocation of dwindling water supply among reservoirs could exacerbate or ameliorate the effects of climate change on aquatic communities. Here, we show that the relative sensitivity of river thermal regimes to direct impacts of climate change and societal decisions concerning water storage vary substantially throughout a river basin. In the absence of interspecific interactions, future Colorado River temperatures would appear to benefit both endemic and nonnative fish species. However, endemic species are already declining or extirpated in locations where their ranges overlap with warmwater nonnatives and changes in water storage may lead to warming in some of the coolest portions of the river basin, facilitating further nonnative expansion. Integrating environmental considerations into ongoing water storage negotiations may lead to better resource outcomes than mitigating nonnative species impacts after the fact.

Water Temperature Modeling Platform Mid-Term Review

Delta Stewardship Council (Delta Council) | October 21st, 2021

Water Wasted to the Sea?

University of California, Davis (UC Davis) | July 15th, 2017

Watershed Action Plan Santa Ana Region - Riverside County

Riverside County | January 18th, 2017

The Watershed Action Plan (WAP) for the Santa Ana Watershed Region of Riverside County (SAR) and its Permittees is a requirement of the Riverside County Municipal Separat

The Watershed Action Plan (WAP) for the Santa Ana Watershed Region of Riverside County (SAR) and its Permittees is a requirement of the Riverside County Municipal Separate Storm Sewer System (MS4), Permit Order No. R8-2010-0033 as adopted by the Santa Ana Regional Water Quality Control Board (Regional Board) in January 29, 2010 (2010 MS4 Permit). The purpose of this requirement is to coordinate existing watershed approaches to address water quality and hydromodification impacts resulting from urbanization within the SAR. This requirement is to be achieved by evaluating existing programs relating to the integration of water quality, stream protection, stormwater management, and re-use strategies with land planning policies, ordinances, and plans within each jurisdiction to the maximum extent practicable (MEP). Throughout implementation of the 2010 MS4 Permit along with the development of this plan, the Regional Board has emphasized that the plans for each jurisdiction should address cumulative impacts of development on vulnerable streams; preserve or restore, consistent with the MEP standard, the structure and function of streams; and protect surface water and groundwater quality.