Supply and Demand Assessment (SDA) - Sonoma Creek
Overview
Sonoma Creek is one of the major tributaries to the San Pablo and San Francisco Bays. The watershed covers approximately 170 square miles, and its elevation ranges from near sea level to approximately 2,723 feet. Sonoma Creek originates northeast of Kenwood at the heart of Sugarloaf Ridge State Park, where it flows southwest to converge with the tributaries descending from the Mayacamas and Sonoma Mountains. The river then flows for approximately 33 miles before descending towards San Pablo Bay. The watershed has a Mediterranean climate with distinct wet and dry seasons, and the land cover is mainly grassland and shrubland.
The Sonoma Creek watershed represents an important habitat for native aquatic species and spawning ground for anadromous fish, especially chinook salmon and steelhead trout. The initial decline in anadromous fish populations within the Sonoma Creek watershed was linked to an increase in sediment. The conservation of these species and their habitat, among other environmental concerns, led to the development of Total Maximum Daily Loads (TMDLs) for nutrients, pathogens, and sediment in 2011 and 2008. Major restoration projects and plans resulted in the delisting of Creek's TMDL for nutrients in 2014.
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Announcements
May 27, 2026 - Sonoma Creek Watershed Model Work Plan - Now Available
The work plan from Paradigm Environmental for development of a hydrologic model for the Sonoma Creek watershed is now publicly available in Model Development section below. Please email questions regarding the model development to DWR-SDA@waterboards.ca.gov.
Model Development
Outreach and Engagement
- Sonoma Creek Watershed Fact Sheet Coming Soon
Modeling in the Sonoma Creek Watershed
The SDA Unit has continued to work on the models and tools developed for the Russian River Watershed during the State Water Board's 2021-2022 Regional Drought Response. These tools provided the necessary information for the Division of Water Rights (Division) to assess water availability and issue water right curtailments to ensure adequate, minimal water supplies for critical purposes under the emergency regulation.
To capture the water demand in the SDA Program Watersheds, water right demand estimates were incorporated based on information from annual reports of water diversion and use submitted to the Division. The SDA Unit continued to develop the Division's demand dataset methodology and converted it into a series of R scripts and manual review spreadsheets that apply data quality correction flags. For example, the scripts identified and corrected unit conversion errors, duplicate reporting, and misplotted points of diversion. The SDA Unit then uses a water allocation tool adopted from the UC Davis Drought Water Rights Allocation Tool (DWRAT) to allocate available supply amongst water right holders based on their respective water right priority and water demands. This version of DWRAT allocates water at the subbasin level and accounts for imported flows.
The SDA Unit's demand methodology, along with the supply scripts and the watershed specific versions of DWRAT, will be made available on the California Water Board Data Center GitHub page as separate repositories.
Supply and Demand Assessment Program Links
Supply and Demand Assessment Information
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Contact Us
If you have questions or please email them to: DWR-SDA@waterboards.ca.gov
