State Water Board presents new watershed supply‑and‑demand models, plans public review and dashboards

Division of Water Rights staff told the State Water Resources Control Board on Sept. 3 that a multi‑year program is developing hydrologic supply‑and‑demand models and public dashboards for 18 watersheds to support local planning and future board decision making. Philip Dutton, program manager for the Supply and Demand Assessment (SDA) program, said the effort grew from the Russian River drought response and that the board has contracted Paradigm Environmental to develop models under a $15,000,000 contract.

Dutton and senior engineer Mohammad Sarabi explained that the models use the LSPC (Loading Simulation Program in C++) framework and rely on meteorological inputs, streamgage flow records, cleaned annual water‑use reports and geospatial watershed delineations. Dutton described a staged development process—work plans, data collection, model configuration, calibration/validation and final reports—and said staff will post work plans and model reports for public review as each watershed completes draft documents. The Navarro River draft report was released for comment through Oct. 9; others (e.g., Wallala River, Salmon Creek) will follow.

Sarabi described calibration and validation procedures (e.g., Navarro model calibrated on 2018, validated on 2004–2017) and demonstrated dashboards planned for water‑use demands, historic/current supply & demand estimates, and monthly updates. He said water‑use demand dashboards for nine watersheds are published and that, once models are finalized, staff will provide monthly supply and demand updates and run scenario analyses. Dutton emphasized these tools are intended to support local decision making—allocation exercises, voluntary water‑sharing programs, feasibility assessments for wet‑season storage, and technical assistance to GSAs (Groundwater Sustainability Agencies).

Why it matters: The modeling suite aims to provide consistent, accessible data for diverters, local agencies and the board so responses to future droughts can be better targeted and informed. Dutton said staff engagement in watersheds can also encourage improved water‑use reporting, and he described coordination with the division's Water Rights data system (CalWaterS upgrade) to enhance data flows.

Board discussion and next steps: Board members praised outreach and asked about groundwater–surface water interactions. Staff said LSPC models approximate groundwater where appropriate but will incorporate groundwater model outputs or partner with local GSAs when simple assumptions are insufficient. Staff plan technical workshops, monthly model runs and an availability of models for interested parties to run scenarios. A mid‑2026 update to the board was suggested.

Ending: Staff encouraged interested parties to subscribe to the program listserv and to review posted work plans, dashboards and draft reports on the program web page.