Water Supply & Storage

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

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

Harvest Sources

This dataset contains the daily elevation and storage data for the State Water Project reservoirs.

Updated Oct 7, 2026

Harvest Sources

DWR continuous groundwater level measurements contains continuous time-series data from automated recorders at sites operated by the Department of Water Resources. Readings are taken at 15-minute to one-hour intervals. Some of the readings are relayed to the California Data Exchange Center. However, most of the monitoring sites are visited once every month or two, when readings are off-loaded from data recorders, then finalized and published. Wells monitored for this dataset are located within Butte, Colusa, Glenn, Mendocino, Modoc, Sacramento, San Joaquin, Shasta, Siskiyou, Solano, Sutter, Tehama, Yolo, and Yuba Counties. Water-level measurements are the principal source of information about changes in groundwater storage and movement in a basin, and how these are affected by various forms of recharge (e.g., precipitation, seepage from streams, irrigation return) and discharge (e.g., seepage to streams, groundwater pumping). Water-level monitoring involves "continuous" or periodic measurements. Continuous monitoring makes use of automatic water-level sensing and recording instruments that are programmed to make scheduled measurements in wells. This provides a high-resolution record of water-level fluctuations. Resulting hydrographs can accurately identify the effects of various stresses on the aquifer system and provide measurements of maximum and minimum water levels in aquifers. Continuous monitoring may be the best technique to use for monitoring fluctuations in groundwater levels during droughts and other critical periods when hydraulic stresses may change at relatively rapid rates, or when real-time data are needed for making water management decisions [see usgs reference](https://ca.water.usgs.gov/sustainable-groundwater-management/groundwater-levels-california.html).

Updated Oct 7, 2026