Cachuma Reservoir


March 2019 Cachuma 2

In 1945, the Water Agency was established by the State of California.  The Water Agency entered into a master contract with the United States Bureau of Reclamation (USBR) for development of the Cachuma Project and subcontracts with Carpinteria Valley Water District, Montecito Water District, the City of Santa Barbara, Goleta Water District, and the Santa Ynez River Water Conservation District Improvement District No. 1, all of which are designated as Member Units of the project.  The project was authorized in 1948, by the Secretary of the Interior pursuant to section 9(a) of the Reclamation Project Act of 1939.  Construction of the Cachuma Project by the USBR began in 1950 and was completed in 1953.

Water is diverted from the reservoir using the 6.4 mile long Tecolote Tunnel through the Santa Ynez Mountains to the South Coast Conduit and distribution systems. The Santa Ynez River Water Conservation District Improvement District No. 1 receives its Cachuma allocation through State Water exchanges with the other member units.

Drainage Area 
417 square miles 
Surface Area Full 
3,200 acres 
Maximum Water Surface Elevation 
753 feet above sea level 
Maximum Capacity 
193,304 acre-feet 
Current Maximum Yield 
25,714 acre-feet per year


USBR Cachuma Project
Current Cachuma conditions 

Cachuma Member Units
Carpinteria Valley Water District 
Montecito Water District 
City of Santa Barbara 
Goleta Water District 
Santa Ynez River Water Conservation District Improvement District No. 1

Federal Cachuma Contracts
Master contract between USBR and Santa Barbara County Water Agency (1949)
Master contract between USBR and Santa Barbara County Water Agency (1996)

Cachuma Operation and Maintenance Board
The Cachuma Operation and Maintenance Board (COMB) formed in 1956 pursuant to an agreement with the USBR. The agreement transferred to the Member Agencies the responsibility to operate, repair and maintain all Cachuma Project facilities, except Bradbury Dam, which the USBR continues to operate.  COMB's Member Agencies include Goleta Water District, the City of Santa Barbara, Montecito Water District, and Carpinteria Valley Water District.  COMB is responsible for diversion of water from Lake Cachuma to the Member Agencies through the Tecolote Tunnel.  In addition COMB operates and maintains the South Coast Conduit pipeline, flow control valves, meters and instrumentation at control stations and turnouts along the South Coast Conduit and at four regulating reservoirs.

Central Coast Water Authority
The Central Coast Water Authority (CCWA) was formed in 1991 to construct, manage, and operate Santa Barbara County's local facilities for distribution and treatment of State Water.  The extension of the Coastal Branch of the State Water Project terminates at Lake Cachuma which is the delivery point and conveyance for State Water to the South Coast agencies.  A contract between CCWA and USBR allows for storage and conveyance of up to 13,750 acre-feet of non-Project water if capacity in the lake is available.

Water Rights Resources
In accordance with State Water Resources Control Board water rights orders, releases are made from the lake at rates, amounts, and times requested by the Santa Ynez River Water Conservation District Improvement No. 1.

The State Water Resources Control Board determines water rights necessary to protect public trust values and downstream water rights on the Santa Ynez River below the Bradbury Dam.  The most recent Cachuma Project water rights order hearing information can be found on the State Water Board's Cachuma Project webpage.

Cachuma Conservation Release Board was established in 1973 to represent its members (currently the City of Santa Barbara, Goleta Water District, and Montecito Water District) in protecting their Cachuma Project water rights and other related interests.  

The National Marine Fisheries Service (NMFS) issued a Biological Opinion (BO) in 2000 for the USBR's operation and maintenance of Bradbury Dam.  The BO examined the effects of the Cachuma Project operations on Southern California steelhead (Oncorhynchus mykiss) in accordance with Section 7 of the Endangered Species Act of 1973.  The BO addresses operations to improve habitat conditions downstream of Bradbury Dam for the steelhead while maintaining current water deliveries.  NMFS concluded that Cachuma Project operations are not likely to jeopardize the continued existence of steelhead.  
Recreation is one of the indirect benefits of the Cachuma Project.  USBR owns the 3,000 acre lake and 6,200 acres of land surrounding the lake.  Under contract with USBR, the County Parks Department operates and maintains the 375 acre Cachuma Lake Recreation Area on the south shore of the lake.  The original operation and maintenance contract was signed in 1953.  The most recent management agreement was executed in 2011 which allows for the continued operation and maintenance of the Recreation Area through 2036.  

Costs to Excavate Cachuma 
Frequently the question comes up about excavating Cachuma Reservoir while the Lake is low as a way to increase storage and water supplies. While this sounds like a good idea, in reality the costs of such a move makes little sense.  To quantify the costs it is best to put the project into perspective in terms of overall costs, and costs per acre-foot.

Cachuma functions as a true reservoir and as such the volume of the lake is not utilized in a single year, but rather stores water in wet years to last through a critical drought period.  As such, the excavation of materials must be allocated over the drought period.  For Cachuma, that requires about a 10-1 ratio of volume excavated to yield provided.  This accounts for evaporation and other losses in the reservoir.

So for ease of calculation, we will assume that we desire to get 1,000 acre-feet of yield out of Cachuma. Thus we need to excavate 10,000 acre-feet of new volume.  The cost breakdown is as follows:
10,000 acre-feet equals 16.1 million cubic yards.
At $10 per cubic yard (conservatively low) that renders an excavation cost of $161 million.
Adding in environmental, permitting, engineering, and construction management (25%), that leaves us at about $200 million.

NET PER ACRE FOOT COSTS = $200,000 per acre-foot

Technical issues with the project could easily increase these costs several fold.  First, it needs to be recognized that one cannot dig a 10,000 acre-foot hold in the lake.  The sedimentation is spread out over the lake bottom so in effect one must either skim this material over 100's of acres, or a localized excavation that can ensure connection to the lake (not stranding this volume) that still covers a sizable area.

The material needs to be trucked, or a location found close to place the excavated material that ensures it does not re-enter the lake.  In calculating the costs, there was no allowance for property acquisition either, so as such the costs of this work could be significantly higher.

Thus, at a cost of over $200,000 per acre-foot, there are many other options for water supply that are more economic and less environmentally harmful.  


Bradbury Dam and Cachuma Reservoir