COMMITTEE AGENDA MEMORANDUM
Agricultural Water Advisory Committee
Government Code § 84308 Applies: Yes ☐ No ☒
(If “YES” Complete Attachment A - Gov. Code § 84308)
SUBJECT: title
Receive an Update on Valley Water’s South County Managed Aquifer Recharge Activities.
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RECOMMENDATION:
Recommendation
Receive an update on Valley Water’s South County managed aquifer recharge activities.
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SUMMARY:
Managed aquifer recharge continues to be essential for groundwater sustainability throughout Santa Clara County, but particularly in South County where local communities depend almost entirely on groundwater. Valley Water’s managed recharge using local and imported surface water helps balance groundwater pumping, and long-term planning helps ensure continued reliability far into the future. This memorandum describes Valley Water’s South County recharge program and related projects that are being evaluated as part of the Water Supply Master Plan 2050.
Background
For many decades, the amount of groundwater pumped in Santa Clara County has exceeded what is replenished naturally by rainfall or other sources. To ensure local groundwater supplies are sustainable, Valley Water augments natural groundwater recharge through the managed recharge of local and imported surface water. Water conservation and recycling programs as well as treated water deliveries (North County only) also protect groundwater supplies by reducing the need for groundwater pumping.
Each year, Valley Water determines optimal water supply operations, including managed recharge, based on available supplies and local needs. Long-term water reliability is evaluated through Valley Water’s Water Supply Master Plan and Urban Water Management Plan, which assess projected future supplies and demands and are updated every five years. Investments and projects to meet projected future shortfalls and ensure continued reliability are identified in the Water Supply Master Plan.
Current South County Recharge Facilities
South County overlies all or part of both primary groundwater basins in the county. This includes the Coyote Valley portion of the Santa Clara Subbasin (which extends north from the Cochrane Road area in northern Morgan Hill to the Coyote Narrows near Metcalf Road in San Jose) and the entire Llagas Subbasin (which extends south from Cochrane Road to the Pajaro River that forms part of the boundary with San Benito County). Based on 2016 to 2025 data, average South County annual pumping is 54,800 acre-feet per year (AFY), while natural recharge is estimated to be 26,100 AFY. To address this imbalance, Valley Water recharges 37,800 AFY of local and imported surface water, on average.
Using established local surface water rights at Uvas, Chesbro, Coyote, and Anderson reservoirs, Valley Water captures and stores large volumes of upper watershed stormwater runoff for delivery to groundwater recharge facilities in South County. Valley Water also has contracts with both the State Water Project and Central Valley Project to receive imported water via San Luis Reservoir and the federal San Felipe Division system and uses it for managed recharge in South County. In-stream and off-stream recharge facilities are located in areas with permeable soils that are connected to deep drinking water aquifers.
Valley Water operates three groundwater recharge systems in South County as shown in Attachment 1. Releases into Coyote Creek replenish groundwater in the Coyote Valley and extend into North County. The Upper and Lower Llagas recharge systems replenish the Llagas Subbasin, which support communities in the cities of Morgan Hill and Gilroy as well as unincorporated areas including San Martín. In addition to municipal wells, thousands of privately owned domestic, agricultural, and industrial wells depend on local groundwater. As summarized in Table 1, the annual recharge capacity of South County managed recharge facilities is over 54,000 AFY, with most capacity in creeks as compared to off-stream ponds. Attachment 2 provides more detailed information on the recharge capacity of individual facilities within the South County recharge systems.
Table 1 - South County Managed Recharge Facility Capacity Summary
|
Groundwater Management Area |
In-Stream Recharge (AFY) |
Off-Stream Recharge (AFY) |
Total Recharge (AFY) |
|
Coyote Valley (Santa Clara Subbasin) |
14,600 |
0 |
14,600 |
|
Llagas Subbasin |
25,000 |
14,700 |
39,700 |
|
Total |
39,600 |
14,700 |
54,300 |
Note: The annual recharge capacity shown assumes water is available all year and that ponds are in normal operational condition.
Potential South County Recharge Projects
Valley Water’s investments in reservoirs, imported water, and managed recharge facilities and operations have ensured reliable South County groundwater conditions for many decades. Valley Water closely monitors groundwater levels and prioritizes recharge to groundwater-dependent communities like South County, particularly during droughts. Groundwater recharge is essential for long-term reliability and has played a critical role in quick drought recovery. With "weather whiplash" (frequent shifts between extremely wet and dry years) becoming more common and the high, local reliance on groundwater, there is a need for additional recharge capacity in South County.
Several South County managed recharge projects were evaluated through the Water Supply Master Plan 2050 that was adopted by the Board of Directors on November 12, 2025. The proposed recharge projects include:
a) Madrone Channel Expansion - to increase recharge capacity to the existing facility by adding one or two ponds on land owned by Valley Water;
b) Coyote Valley Recharge Pond - to construct a new off-stream recharge pond(s) near the Cross Valley Pipeline to increase operational flexibility, reduce reliance on Coyote Creek flows, and help balance increased pumping;
c) Butterfield Channel Recharge - to connect the Butterfield Channel that is owned by the City of Morgan Hill to Valley Water’s raw water conveyance system so imported water can be recharged when the channel is not used for stormwater flows; and
d) San Pedro Ponds Improvement Project - to implement project(s) to enable the existing seven ponds to be operated at full capacity without interfering with septic systems on several adjacent residential properties in the unincorporated areas of Santa Clara County.
Not all four managed recharge projects are needed to ensure reliable groundwater supplies, and most of these projects are in the early conceptual phase. More substantial evaluation was conducted for the San Pedro Ponds, and an optimization study identified eight alternatives that could fully or partially restore the 4,700-AFY operating capacity of the San Pedro Ponds. The study looked at addressing the impacts of high groundwater table on septic systems in properties surrounding the San Pedro Ponds. Staff will continue to evaluate which of the four managed recharge projects will best support water supply needs.
In addition to managed recharge projects at Valley Water facilities, staff continue to explore the feasibility of Flood Managed Aquifer Recharge (Flood-MAR) in Santa Clara County to augment Valley Water’s extensive managed recharge program. Staff presented the pre-feasibility study report at the August 22, 2023, Water Conservation and Demand Management Committee and the October 2, 2023, Agricultural Water Advisory Committee meeting. Since then, staff reviewed water supply benefits of potential sites, as well as several Flood-MAR projects in the region. Lessons learned indicate that it often takes multiple years for a Flood-Mar project to be constructed, water supply benefits are small and intermittent, and the projects require on-going management and maintenance. Thus far, no feasible site has been identified for Flood-MAR.
Injection Wells
At the Agricultural Water Advisory Committee meeting of January 5, 2026, committee member Erin Gill requested a discussion of the pros and cons of direct injection with recycled water within the Santa Clara County. Attachment 3 includes a summary of the pros and cons of instream recharge and recharge ponds versus injection wells for managed recharge. In summary, staff favor the use of instream recharge and recharge ponds and do not recommend using injection wells because of the risk to groundwater quality, operational complexity, and increased costs.
ENVIRONMENTAL JUSTICE IMPACT:
There are no environmental justice impacts associated with this item.
ATTACHMENTS:
Attachment 1: South County Recharge Facility Map
Attachment 2: South County Recharge Facility Capacity
Attachment 3: PowerPoint
UNCLASSIFIED MANAGER:
Manager
Gregory Williams, 408-630-2867