Office of the Delta Watermaster

Important Information about Water Reporting for Water Year 2023 for Water Reporters in the Legal Delta under California Law

All water use reports are due before June 1, 2024.

The Delta ACP website is now live for water reporting in the legal Delta ( for both statement and license reporting. As a result of technical challenges in bringing the Delta ACP website online for filing license reports, the Office of the Delta Watermaster is EXTENDING THE DEADLINE FOR WATER YEAR 2023 REPORTING TO JUNE 15, 2024 for filers on the DeltaACP platform.

We greatly appreciate all efforts to migrate reporting to the website in the Legal Delta. The importance of gaining a shared understanding and greater accuracy of consumptive water use in the Delta remains a leading priority of the Office of the Delta Watermaster.

In this regard, we also greatly appreciate the continued research, experiments and dialogue of the Delta Measurement Experimental Consortium, which will meet next on Wednesday, May 22, 2023 from 3:00 p.m. to 4:30 p.m..

Pursuant to 23 CCR §936, diverters seeking coverage under the Delta ACP are hereby granted an extension of time to complete reporting by June 15, 2024, so as to accommodate the additional time required to update the Delta ACP user interface for license reporting.

Please note that the Office of the Delta Watermaster is encouraging all eligible water users within the Legal Delta to file their WY 2023 Supplemental Statements of Water Diversion and Use (for their Statement Numbers [“S0____”]) and Reports of Licensee (for their Licenses [“A0____”]) through the Delta Alternative Compliance Plan website ( The Delta ACP reporting platform provides a singular repository to better measure and understand actual consumptive use in the Legal Delta.

The Office of the Delta Watermaster – Background

The Office of the Delta Watermaster was created as part of the Delta Reform Act of 2009. The Watermaster is an independent officer of the State, appointed to a four-year term by the State Water Resources Control Board, reporting jointly to the Water Board and to the Delta Stewardship Council.

Important Reminder!

Water Rights Reporting

Delta Measurement Experimentation Consortium

Overlap Memo

2015 Informational Order

  Access the 2015 Informational Order FTP Document Repository

Username: IORR-FTP
Password: AccessIORR

General Water Rights Resources


The Watermaster is responsible for overseeing the day-to-day administration of water rights, and, when necessary, for taking enforcement action, related to water diversions within the Delta. The Watermaster also confers with and assists both the Water Board and the Stewardship Council as they carry out their respective legislative mandates to achieve the dual objectives of enhancing the Delta ecosystem and improving water supply reliability within the constraints of the water rights system and of the Delta as an evolving place.

The Delta – The Hub of California’s Water Management System

The Delta is an inland estuary located at the confluence of the Sacramento and San Joaquin Rivers just before their outlet to San Francisco Bay and the Pacific Ocean. The Delta is comprised of a network of islands, channels and wetlands which make up the largest estuary on the Western Coast of the United States. The Delta is the hub of California’s water management system as well as an important ecological system supporting a variety of species, several of which are protected under endangered species acts. The Delta ecosystem and the water management facilities located there are under pressure from a variety of natural and man-made stressors including:

  • water diversions from its natural tributaries;
  • withdrawal of a portion of its water to meet the needs of users throughout the State;
  • invasive species which compete with or prey upon its endangered natives;
  • the constant risk of salinity intrusion from the Ocean and of salinity concentration by farming;
  • degradation in its water quality from historic causes such as hydraulic mining and current causes such as farm and urban runoff;
  • channelization of its waterways and the fragility of some of its levees;
  • oxidation and erosion of friable peat soils which have left some islands subsided below the surrounding water table;
  • complex (and sometimes conflicting) regulatory constraints; and
  • a clash of public and private interests that has generated decades of litigation and conflict.

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Delta Waterway
Photo credit: Department of Water Resources


For Questions or Comments
Contact the Office of the Delta Watermaster:

Phone: 916-319-8264

U.S. Mail:
Office of the Delta Watermaster
State Water Resources Control Board
P.O. Box 100
Sacramento, CA 95812-0100

Delta Challenges