Are there plans to fill more of Valley Water’s percolation ponds in Santa Clara County this summer?

As people enjoy local trails this summer, they may notice some of Valley Water’s percolation ponds in Santa Clara County are empty and dry.

There’s no reason to be alarmed. In fact, the absence of water in some of Valley Water’s 102 percolation ponds is a sign that our groundwater basins are mostly full and healthy.

Percolation ponds are water supply facilities built in areas where permeable gravel and sand allow water to seep into underground aquifers. The ponds’ primary and most important purpose is to allow water to filter underground to maintain healthy groundwater conditions. The ponds were not created to support wildlife, although many types of birds, fish and other animals take advantage of these ponds when water is available. When the ponds are dry, animals often find other nearby bodies of water to enjoy.

Our groundwater basins remain mostly full and healthy thanks to careful water management and abundant water supplies the past two rainy seasons. In 2023, Valley Water implemented a full groundwater recharge program which kept percolation ponds across Santa Clara County filled with water during the summer and fall. Valley Water sent more than 100,000 acre-feet of local and imported surface water into aquifers in 2023.

However, we do not want to overfill the groundwater basins, which would happen if we continued to release water into all percolation ponds.

Refilling more percolation ponds could result in increased artesian pressure underground, which could bring water to the surface via abandoned wells, causing localized flooding. This could cause problems in the cities of San Jose, Santa Clara, and neighboring cities on the valley floor. Artesian wells occur naturally over large areas of Santa Clara Valley and do not require a pump to bring water to the surface.

Our groundwater scientists and engineers assess water supplies and needs often and regularly track the water levels in the aquifers. We will refill more ponds when the groundwater conditions warrant it.

However, many of Valley Water’s percolation ponds across Santa Clara County are expected to have water for the remainder of 2024. North County percolation ponds in operation include the:

• Dr. Robert W. Gross Ponds, Piedmont Ponds, and City Park Pond in East San Jose
• Oka, McGlincy, Camden, Page and Sunnyoaks ponds in Campbell
• McClellan Ponds in Cupertino
• Los Capitancillos Ponds and Alamitos Pond in South San Jose

Valley Water continues prioritizing groundwater recharge in South County. These communities, including residents and farmers, depend almost entirely on groundwater for their water supply needs. Valley Water recently completed inspection and repair of the Santa Clara Conduit, which brings imported surface water to the county from San Luis Reservoir. With that important work done, Valley Water will maximize groundwater recharge in South County in the following percolation pond systems:

• Madrone Channel and Main Avenue Ponds in Morgan Hill
• San Pedro Ponds (at a limited capacity due to work on pipes)

We will continue to carefully manage our precious water supplies to ensure safe, clean water for the community. And just a reminder, every drop saved is water we can use in the future. Check out our conservation rebates and programs at watersavings.org.