Delta Watermaster: CalWaters launch and OpenET data improve Delta measurement; warns of federal science cuts

Delta Watermaster Jay Ziegler told the board on July 16 that the office is preparing for a broader rollout of the state’s new CalWaters reporting platform and that OpenET and a Delta Measurement Experimental Consortium are improving the board’s ability to estimate consumptive use across the legal Delta. "This Cal Waters data system [was delivered] on time and on budget," Ziegler said, and he described the reporting transition as "a process" that will mature as the agency integrates alternative compliance programs and agent training.

Why this matters: CalWaters and OpenET data aim to reconcile diversions reported at points of diversion with downstream consumptive use, a relationship essential to managing flows and protecting beneficial uses in the Delta. Ziegler told the board the Delta has roughly 2,800 water‑rights entries and about 1,000 unique owners; high compliance reporting (the office cited about 98% reporting) gives the Watermaster a clearer basis to analyze diversion patterns and to spot outliers.

Technical updates and pilots: Will Anderson, the Watermaster’s senior engineer, summarized comparative data. He reported that OpenET‑derived consumptive‑use estimates account for about two‑thirds of the Delta estimates and that some in‑Delta programs are filing via the Delta Alternative Compliance Platform (Delta ACP). Anderson said the top 10 owners account for about one‑third of reported in‑Delta diversions and that most large owners have registered measuring devices; where devices are lacking, the measurement consortium and OpenET can help fill gaps. The consortium is now working with organizations such as the Metropolitan Water District, the Nature Conservancy and UC researchers to deploy pilot measurement projects, including island‑scale diversion metering and eddy‑covariance flux studies.

Sediment management and special projects: The Watermaster reported new momentum on organized sediment management after observing sandbar formation and navigation blockages in previous high flows. Ziegler said the Department of Water Resources has circulated a revised memorandum of understanding intended to coordinate state, federal, tribal and local agencies for expedited dredging and pilot projects in the South Delta.

Funding and federal cuts: Ziegler warned of a troubling federal budget trend that could reduce key monitoring and research programs. He said the U.S. Bureau of Reclamation’s Western Office had already absorbed a 20% reduction and additional cuts were proposed; other federal reductions flagged included cuts to the Pacific Salmon Restoration Fund and to NOAA research budgets. "We are in an alarming moment," Ziegler told the board, and he urged continued state attention to retain critical data continuity and quality for Delta decision‑making.

No formal board actions were proposed. The Watermaster stressed continued coordination with CalWaters, regional boards and the Delta Measurement Experimental Consortium to refine measurement approaches and agent training for the October reporting period.

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