The Tri-Valley Water
Zone 7 Water is the water wholesaler for the region and is charged with ensuring water continues to flow on this elaborate journey over hundreds of miles to get to the Tri-Valley community. As the water wholesaler, it serves as the lead agency in exploring and participating in the various planning and implementation phases of long-term water reliability projects, many of which can take 10-20 years to plan, fund, and construct. The agency collaborates closely with the retail partners and the community throughout the planning stages to ensure the community is educated about the costs and benefits of these projects.
Currently, the Tri-Valley area imports 70% of its water through the Delta and the South Bay Aqueduct. The local groundwater basin provides a mechanism to store some of that imported water for increased reliability during short term drought cycles, however, we need other resources to sustain our community for extended periods of drought.
The goals of the Tri-Valley water reliability effort are to diversify our water supply, increase conveyance options for water flows into our community, and secure additional storage capacity to ensure we have a reliable water supply system. By exploring these options fully now, we can be prepared to invest in the community’s future water needs. This includes identifying the right combination of projects and securing support for funding these important investments in our community’s future, to be implemented over the next 10-20 years.
At this stage, the Tri-Valley Water Partners are still exploring different opportunities to address our various water supply challenges. Check out the different projects we are studying as potential solutions at this time.
Water Supply Reliability
Bay Area Regional Desalination Project
Five Bay Area water agencies — the Contra Costa Water District (CCWD), the East Bay Municipal Utility District (EBMUD), the San Francisco Public Utilities Commission (SFPUC), the Santa Clara Valley Water District (SCVWD) and Zone 7 Water Agency (Zone 7) — are jointly exploring a regional desalination project where brackish water from the Delta would be desalinated in eastern Contra Costa County and used as a new source of supply for the Tri-Valley and other water agencies. This water could be delivered via a water exchange through the Delta or delivered through a planned intertie that would connect Zone 7’s and EBMUD’s systems.
Key benefits: Desalination provides a drought-resistant water supply from a regional source.
Delta Conveyance Project
Delta conveyance is the movement of water through the network of waterways in the Sacramento-San Joaquin Delta, the hub of the State Water Project – California’s most critical water delivery infrastructure. Multiple sources of water come through the Delta, making the dependability of its infrastructure of critical importance to water reliability for the Tri-Valley.
The State Water Project’s 1960-era infrastructure is aging and needs to be upgraded to meet the challenges ahead including ecosystem decline, seismic risk and climate change/sea level rise. The Delta Conveyance Project would add new conveyance facilities in the Delta, including two new intakes located away from sensitive fish habitat and 20 feet above sea level and a new tunnel. The key benefits of the project to the Tri-Valley are related to the proposed new tunnel that could bypass the southern part of the Delta when the Delta is unusable due to poor water quality or the presence of endangered or threatened species. The project would therefore increase SWP reliability and improve water quality.
Key benefits: The proposed Project would increase the reliability of the SWP system and improve water quality while protecting the Delta ecosystem.
Los Vaqueros Reservoir Expansion and Transfer Bethany Pipeline
The Los Vaqueros Reservoir is an off-stream reservoir located in southeastern Contra Costa County with a capacity of 160,000 acre-feet. Contra Costa Water District is planning to expand the reservoir to 275,000 acre-feet and construct the Transfer-Bethany Pipeline, to connect the reservoir to Bethany Reservoir and the South Bay Aqueduct (SBA) system, which are part of the SWP system.
While the project could potentially provide new supplies from the Delta, Zone 7 is primarily evaluating the Project as additional local storage upstream of Zone 7’s system, making it more accessible. Zone 7 could store excess supplies in Los Vaqueros Reservoir for later use during droughts or emergencies when supplemental supplies are needed. With a new connection to the SBA, the Project also provides the benefit of emergency conveyance, a crucial element for when there are pumping restrictions in the Delta, thus adding much needed operational flexibility, particularly in times of drought.
Key benefits: The project would improve water supply reliability by increasing accessible local storage and providing alternative/emergency conveyance when Delta pumping is restricted.
The Sites Reservoir project offers a unique opportunity to construct a new multi-benefit water storage infrastructure project that helps to achieve local, state and federal goals for water supply reliability, the environment, the economy and flood protection.
The 1.5 million acre-foot off-stream reservoir will capture and store stormwater flows from the Sacramento River increasing Northern California’s surface storage capacity by 15 percent. Water stored in Sites Reservoir will then be available for use during drier years, while also contributing to renewable energy goals, providing groundwater recharge and year-round recreational opportunities. Sites Reservoir will be operated to improve water supply resilience to climate change, increasing our statewide water reliability when it’s most needed. Sites Reservoir offers the potential for a significant source of new supply for the Tri-Valley - about 10,000 acre-feet per year--and storage that will be located upstream of Zone 7’s system. This water could be used during both normal years and dry years to supplement other supplies.
Key benefits: The Sites Reservoir would provide a significant source of new supply for use during normal and dry years.
A water transfer is the sale of water from a willing seller (with extra supplies) to a willing buyer. In a water exchange, a portion or all of that water may be returned to the seller within a given time. Water transfer/exchange agreements can be made between Zone 7 and a private entity, an agricultural district, and/or other water agencies (e.g., a municipal SWP contractor). They can be short-term (one year) or long-term agreements. Water transfers/exchanges can be used to fill water supply gaps until more permanent solutions are in place.
Key benefits: Transfers and exchanges can be implemented immediately using existing infrastructure.
Groundwater Banking Programs
Zone 7 has agreements with Semitropic Water Storage District and Cawelo Water District in Kern County for 78,000 acre-feet and 120,000 acre-feet of storage capacity, respectively. Zone 7 stores excess supplies during wet years then withdraws stored water from these banks when needed during dry years (e.g., 2014 and 2021) to supplement low surface water supplies. Water is delivered via the South Bay Aqueduct as surface water and then deducted from these banks via exchange with other State Water Project contractors.
Key benefits: The groundwater banks provide a source of supplemental water supply during dry years and emergencies, and use existing SWP infrastructure for delivery.
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