Water

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

The Groundwater Sustainability Plan (GSP) Annual Report (AR) datasets contain the following data submitted by Groundwater Sustainability Agencies (GSA) and Alternative Agencies as part of their GSP AR or Alternative to GSP AR: groundwater extraction, surface water supply, total water use, and change in storage volumes for a given water year. All data was originally submitted to the Department of Water Resources (DWR) through the Sustainable Groundwater Management Act (SGMA) Portal’s AR Modules (https://sgma.water.ca.gov/portal/gspar/submitted and https://sgma.water.ca.gov/portal/alternative/annualreport/submitted). Data records within each dataset correspond to either an entire basin or one of multiple GSP areas which collectively correspond to an entire basin. The GSP Regulations established the AR data requirements (23 CCR § 356.2) and tasked DWR with developing an online reporting system for GSAs and Alternative Agencies to electronically submit these data (23 CCR § 353.2). The data fields associated with these datasets were created by DWR to ensure GSAs and Alternative Agencies electronically submitted the required AR data to DWR’s online reporting system, the SGMA Portal (https://sgma.water.ca.gov/portal/). For additional information regarding the AR Modules and the AR submittal process, please view the DWR’s AR resources (https://sgma.water.ca.gov/portal/resources).

Updated Oct 7, 2026

Harvest Sources

The Groundwater Sustainability Plan (GSP) Monitoring dataset contains the monitoring sites and associated groundwater level, subsidence or streamflow measurements collected by Groundwater Sustainability Agencies (GSA) during implementation of their GSP. All data is submitted to the Department of Water Resources (DWR) through the Sustainable Groundwater Management Act (SGMA) Portal’s Monitoring Network Module (MNM). The GSP Regulations established the monitoring network criteria (23 CCR § 354.34) and the data and reporting standard for monitoring sites and measurements (23 CCR § 352.4). The data fields associated with these datasets were created by DWR to ensure that GSAs electronically submit monitoring site and measurement data which meets the GSP Regulation’s data and reporting standards. For additional information regarding GSAs, GSPs, and SGMA related monitoring, please view DWR’s SGMA Portal Resources at https://sgma.water.ca.gov/portal/.

Updated Oct 7, 2026

Harvest Sources

In California, water systems serving one (1) to 15 households are regulated at the county level. Counties vary in their practices, but rarely do counties collect data regularly from these systems. Even where data is collected, it is entirely voluntary. A review of well permit information suggests there are over 1 million such water systems in California. In early 2014, a cross-agency Work Group created an easily accessible reporting system to get more systematic data on which parts of the state had households at risk of water supply shortages. The initial motivation for local water supply systems to report shortage information was to obtain statewide drought assistance. The reporting system receives ongoing reports of shortages from local, state, federal and non-governmental organizations, and tracks their status to resolution. While several counties have developed their own tracking mechanisms, this data is manually entered into the reporting system. The cross-agency team, led by DWR, seeks to verify and update the data submitted. However, due to the volunteer nature of the reporting and limitations on reporting agencies, collected data are undoubtedly under-representative of all shortages to have occurred. In addition, reports are received from multiple sources and there are occasionally errors and omissions that can create duplicate entries, non-household water supply reporting, and under-reporting. For example, missing information or no data for a given county does not necessarily mean that there are no household water shortages in the county, rather only that none have been reported to the State.

Updated Oct 7, 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