Supply and Demand Assessment (SDA) - Big Creek
Overview
The Big Creek Watershed encompasses approximately 235 square miles along California's Central Coast and drains directly into the Pacific Ocean. Please note that the modeling domain includes Big Creek and some neighboring watersheds Big Creek itself is a free-flowing river, and the broader region includes several notable coastal streams such as the Big Sur River, San Carpoforo Creek, and Willow Creek. Originating on the western slopes of the Santa Lucia Mountains, these rivers generally flow east to west before reaching the coast. Ecologically, Big Creek and its neighboring rivers provide critical habitat for steelhead trout. These streams support important spawning and rearing areas as well as diverse aquatic and riparian ecosystems. Wildfire is a significant environmental stressor, driven by the area's dense and flammable vegetation. Post-fire flooding and sedimentation can severely impact stream habitats, while steep slopes and seismic activity contribute to erosion. The Big Sur River, another key steelhead stream within the broader coastal region, has seen declining populations in recent years due to reduced streamflow.
The watershed experiences a Mediterranean climate, with cool, wet winters and warm, dry summers. Mean annual precipitation varies across the region, averaging 42.5 inches in the northern Big Sur basin, 47.9 inches in the central Big Creek basin, and 35.4 inches in the southern San Carpoforo Creek basin. Land cover is dominated by shrub/scrub (35%), grassland/herbaceous (26%), and evergreen forest (25%) communities, with smaller portions of mixed forest (11%) and developed open space (2%).
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Announcements
May 27, 2026 - Big Creek Watershed Model Work Plan - Now Available
The work plan from Paradigm Environmental for development of a hydrologic model for the Big 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
- Big Creek Watershed Fact Sheet Coming Soon
Modeling in the Big 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
Project Watersheds:
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Contact Us
If you have questions or please email them to: DWR-SDA@waterboards.ca.gov
