Water Quality

California State Water Resources Control Board

Changes to instream flow are known to be one of the major factors that affect the health of biological communities. Flow alteration can degrade physical habitat and alter water quality, reducing the ability of a stream to support aquatic life. Understanding the relationship between changes in flow and changes in benthic invertebrate communities (a key indicator of stream health) is critical to informing decisions about ecosystem vulnerability, identifying causes of stream and watershed degradation, and setting priorities for future watershed management. Among the range of approaches available for setting flow targets that support biological integrity, a recently completed project in southern California evaluated the Ecological Limits of Hydrologic Alteration (ELOHA) framework to assess the effect of flow alteration on the condition of benthic macroinvertebrate (BMI) communities across the region. The ELOHA framework establishes recommended targets using a process that includes estimation of flow alteration and development of flow-ecology relationships based on the response of biological communities to changes in flow. This project applied to the ELOHA framework to develop regional flow-ecology relationships and targets based on responses in the benthic macroinvertebrate community. The objectives of this project were: 1) Develop a recommended set of flow targets for southern California streams that would maximize the likelihood of maintaining healthy biological communities as indicated by the California Stream Condition Index (CSCI) for benthic invertebrates. 2) Produce a set of tools that can be readily applied to future sites to estimate hydrologic alteration relative to biologically-define targets. This project was led by the **[Southern California Coastal Water Research Project (SCCWRP)](http://www.sccwrp.org/Homepage.aspx)** and developed flow-ecology relationships using data from nearly 600 bioassessment sites sampled over the past eight years. The California Stream Condition Index (CSCI), a measure of biological condition based on benthic macroinvertebrate communities, was calculated at each of these sites (for more information on the CSCI, refer to the **[CSCI Fact Sheet](http://www.waterboards.ca.gov/water_issues/programs/swamp/bioassessment/docs/csci_factsheet.pdf)** and the **[Bioassessment scores map](http://www.waterboards.ca.gov/water_issues/programs/swamp/bioassessment/csci_scores_map.shtml)** that shows statewide CSCI scores and stream hydrologic classifications). The degree of hydrologic alteration at each of these sites was assessed by comparing estimates of present-day and historical flows using a set of regionally calibrated hydrologic models. Differences from historic flow conditions were compared to CSCI scores to estimate the probability of good biological conditions along gradients of increasing hydrologic alteration. The datasets presented here provide the biological and flow metrics calculated for each site to develop recommended flow targets and management priorities at those sites. For more information, please refer the final report for this project, available **[here](http://ftp.sccwrp.org/pub/download/DOCUMENTS/TechnicalReports/974_RecomFlowTargetsForBioIntegrity.pdf)**.

Updated Oct 9, 2026

Harvest Sources

This dataset contains annual validated water loss audit reports submitted to the Department of Water Resources by California urban retail water suppliers, as required under Title 23, California Code of Regulations Section 638.5(c) (Regulation). California Water Code Section 10608.12(af) specifies that urban retail water suppliers are those water suppliers directly providing potable municipal water to more than 3,000 service connections or that supply more than 3,000 acre-feet per year at retail for municipal purposes. The Regulation mandates that urban retail water suppliers with multiple separate potable water systems submit a separate audit for each system, regardless of system size. The dataset includes individual water loss audits for all potable water systems owned by urban retail water suppliers, including reports from water suppliers newly classified as urban retail water suppliers. While all submissions are available at the WUEdata.ca.gov portal, this dataset provides a cleaned version with only the latest submissions (older submissions that were corrected are not included). Water system boundaries for the water system water loss data in this dataset may be available in the Water Board's DDW California Drinking Water System Area Boundaries (SABL) tool. The link to this tool can be found in Additional Resources as part of this dataset. Water loss audits evaluate real water losses (leaks) and apparent water losses (e.g. data errors, water theft) occurring in a potable water distribution system. Estimating the scale and cost of these losses allows utilities to identify opportunities for saving water and recovering revenue. California water loss audit submissions were reviewed by validators and submitted to DWR starting in 2016. The reviews followed the validation methodology detailed in Water Research Foundation Project 4639: Level 1 Water Audit Validation. Level 1 water audit validation aims to: * Identify and, where possible, correct inaccuracies in water audit data and application of methodology. * Evaluate and communicate the uncertainty inherent in water audit data. The data is provided "as is" (as submitted by the water systems). More information on this dataset can be found in the file "Data Source and Notes" available at the on the home page of this dataset.

Updated Oct 7, 2026

Harvest Sources

The California Department of Water Resources (DWR) discrete (vs. continuous) water quality datasets contains DWR-collected, current and historical, chemical and physical parameters found in routine environmental, regulatory compliance monitoring, and special studies throughout the state.

Updated Oct 7, 2026

Harvest Sources

(Webpage Under Development) The Department of Water Resources (DWR) provides Technical Support Services (TSS) to assist Groundwater Sustainability Agencies (GSAs) with the implementation of their Groundwater Sustainability Plans (GSPs) and other local entities to better understand groundwater conditions. These services support data collection, groundwater monitoring, and improved understanding of groundwater conditions to help advance sustainable groundwater management efforts across California. Through the TSS program, DWR has partnered with GSAs and other entities on projects across the state to drill and construct groundwater monitoring wells, install groundwater level recording and telemetry equipment, perform downhole camera and geophysical surveys, and collect and analyze groundwater for general chemistry. The data and reports generated from these efforts are publicly available to support ongoing groundwater management and planning. Additional information can be found on the [Assistance and Engagement webpage](https://water.ca.gov/Programs/Groundwater-Management/Assistance-and-Engagement "Assistance and Engagement webpage"). #Summary of Completed TSS Projects To date, DWR has completed TSS projects in **35 groundwater subbasins**, constructing **234 monitoring wells** at **92 sites** statewide. Each of these wells have been assigned a State Well Number (SWN), have had a Well Completion Report (WCR) submitted to DWRs Online System for Well Completion Reports (OSWCR), and have been registered either through the California Statewide Groundwater Elevation Monitoring (CASGEM) Online System or the Sustainable Groundwater Management Act (SGMA) Portal’s Monitoring Network Module (MNM). Groundwater level data from these wells are collected by the GSA or DWR and submitted to CASGEM and/or the MNM. These data can be viewed on the [Water Data Library (WDL)](https://wdl.water.ca.gov/waterdatalibrary/ "Water Data Library (WDL)"). WCRs for these wells can be found using the [Well Completion Report Map Application](https://dwr.maps.arcgis.com/apps/webappviewer/index.html?id=181078580a214c0986e2da28f8623b37 "Well Completion Report Map Application"). A summary table of completed TSS wells including their associated well name(s), site code(s), SWN(s), and WCR number(s), can be viewed and/or downloaded here: [DWR Completed TSS Wells](https://data.cnra.ca.gov/dataset/completed-tss-wells/resource/5263a74b-aae2-4040-9e69-7bf85b9ff120) An interactive GIS map containing a feature set of all completed TSS wells can be accessed here: [GIS Map of Completed TSS Wells](https://www.arcgis.com/apps/mapviewer/index.html?url=https://services.arcgis.com/aa38u6OgfNoCkTJ6/ArcGIS/rest/services/DWR_Technical_Support_Services_(TSS)_Wells/FeatureServer&source=sd “GIS Map of Completed TSS Wells”) The individual TSS well locations, associated borehole lithologic information, and groundwater level data can be viewed on the [SGMA Data Viewer](https://sgma.water.ca.gov/webgis/?appid=SGMADataViewer#gwlevels “SGMA Data Viewer”) by: 1. Checking the “DWR TSS Wells” box under the “Groundwater Levels” tab on the left side of the screen. 2. Clicking on any one of the well location symbols that appear on the interactive map. 3. Clicking on one of the associated Site Code numbers that appear in the results table. #Completed TSS Projects by Groundwater Subbasin Below is a list of subbasins in which TSS projects have been completed. These projects are organized by DWR Region ([Northern Region]( https://water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Groundwater-Management/Assistance-and-Engagement/Files/Basin-Points-of-Contact/NRO_a11y20250115.pdf “Northern Region”), [North Central Region]( https://water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Groundwater-Management/Assistance-and-Engagement/Files/Basin-Points-of-Contact/NCRO_a11y20230705.pdf “North Central Region”), [South Central Region]( https://water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Groundwater-Management/Assistance-and-Engagement/Files/Basin-Points-of-Contact/SCRO_a11y20241219.pdf “South Central Region”), and [Southern Region]( https://water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Groundwater-Management/Assistance-and-Engagement/Files/Basin-Points-of-Contact/SRO_a11y20250115.pdf, “Southern Region”)). Each subbasin listed below has one or more completed TSS project. As more TSS projects are completed, they will be added to this list. All completed TSS projects have several associated documents and datasets, including a Well Installation Summary Report, TSS Agreement between DWR and the GSA, CEQA Notice of Exemption (NOE), Land Use or License Agreement, Local Drilling Permit, Composite Lithologic Log, Survey Report, and a Water Quality Analytical Report. Some projects also include downhole geophysical logs. These data and reports can be accessed by clicking on the subbasin below in which the project is located. ##Northern Region [Antelope Subbasin](hyperlink "Antelope Subbasin") [Big Valley Subbasin](hyperlink "Big Valley Subbasin") [Butte Valley Subbasin](hyperlink "Butte Valley Subbasin") [Colusa Subbasin](hyperlink "Colusa Subbasin") [Corning Subbasin](hyperlink "Corning Subbasin") [Enterprise Subbasin](hyperlink "Enterprise Subbasin") [Red Bluff Subbasin](hyperlink "Red Bluff Subbasin") [Shasta Valley Subbasin](hyperlink "Shasta Valley Subbasin") [Sierra Valley Subbasin](hyperlink "Sierra Valley Subbasin") [Wyandotte Creek Subbasin](hyperlink "Wyandotte Subbasin") ##North Central Region [Cosumnes Subbasin](hyperlink "Cosumnes Subbasin") [Eastern San Joaquin Subbasin](https://data.cnra.ca.gov/dataset/completed-tss-wells/resource/e2cb0649-70e2-4695-98f6-766521a080fb "Eastern San Joaquin Subbasin") [North Yuba Subbasin](hyperlink "North Yuba Subbasin") [Petaluma Valley Subbasin](hyperlink "Petaluma Valley Subbasin") [Santa Rosa Plain Subbasin](hyperlink "Santa Rosa Plain Subbasin") [Solano Subbasin](hyperlink "Solano Subbasin") [Sonoma Valley Subbasin](hyperlink "Sonoma Valley Subbasin") [South Yuba Subbasin](hyperlink "South Yuba Subbasin") [Tracy Subbasin](hyperlink "Tracy Subbasin") [Ukiah Valley Subbasin](hyperlink "Ukiah Valley Subbasin") [Yolo Subbasin](hyperlink "Yolo Subbasin") ##South Central Region [Delta Mendota Subbasin](hyperlink "Delta Mendota Subbasin") [Kaweah Subbasin](hyperlink "Kaweah Subbasin") [Kern County Subbasin](hyperlink "Kern Subbasin") [Kings Subbasin](hyperlink "Kings Subbasin") [Paso Robles Area Subbasin](hyperlink "Paso Robles Area Subbasin") [Tule Subbasin](hyperlink "Tule Subbasin") [Turlock Subbasin](hyperlink "Turlock Subbasin") ##Southern Region [Borrego Springs Subbasin](hyperlink "Borrego Springs Subbasin") [Cuyama Valley Subbasin](hyperlink "Cuyama Valley Subbasin") [Indian Wells Subbasin](hyperlink "Indian Wells Subbasin") [Indio Subbasin](hyperlink "Indio Subbasin") [Mound Subbasin](hyperlink "Mound Subbasin") [Oxnard Plain Subbasin](hyperlink "Oxnard Plain Subbasin") [Pleasant Valley Subbasin](hyperlink "Pleasant Valley Subbasin")

Updated Oct 7, 2026

California State Water Resources Control Board

Wastewater discharges are regulated by the Water Board. Those regulated are generally required to submit Self-Monitoring Reports to the State or Regional Water Board. Some dischargers submit their reports through the electronic Self-Monitoring Report (eSMR) module of the California Integrated Water Quality System (CIWQS). Generally these are for discharges into surface waters regulated by an individual National Pollutant Discharge Elimination System (NPDES) permit, though other dischargers may be included in this dataset as well. This dataset are the monitoring results that have been submitted as data points after the submitters have been approved for electronic submittals (i.e. after the "all electronic date"). Note that this dataset does not include records where the sampling date falls outside of the years shown below. The excluded records include: records where the sampling date is missing, records where the sampling date is invalid (e.g., records with sampling dates in the future or unreasonably far in the past), and records for samples taken prior to year 2006. The excluded records represent approximately 0.1% of all records in the complete eSMR dataset.

Updated Sep 30, 2026