As people explore local trails this summer, they might notice that some of Valley Water’s approximately 100 percolation ponds in Santa Clara County are dry. There’s no need to worry; our groundwater basins are mostly healthy and full.
Percolation ponds are facilities designed to allow water to seep into underground aquifers, thanks to the permeable gravel and sand in the surrounding areas. Their main purpose is to filter water underground and maintain healthy groundwater conditions. While these ponds aren’t specifically for wildlife, many types of birds, fish, and other animals benefit from them when there’s water. When the ponds dry up, animals often seek out other nearby water sources.
Santa Clara County’s groundwater basins are an important yet unseen part of our water supply. These basins hold more water than all 10 of our surface reservoirs combined, and over 40% of all water used comes from groundwater. Our groundwater basins are healthy thanks to careful management and good water supplies from the last three rainy seasons. In 2023 and 2024, Valley Water implemented a comprehensive groundwater recharge program that kept many percolation ponds throughout Santa Clara County filled during the summer and fall. Over each of the past two years, Valley Water has sent more than 100,000 acre-feet of surface water into the aquifers.
However, we want to avoid overfilling the groundwater basins, which could create increased artesian pressure underground. This pressure could cause water to surface through abandoned wells, leading to localized flooding in areas of San José, Santa Clara and other communities on the valley floor. Artesian wells naturally exist over large areas of Santa Clara Valley and do not need pumping to bring water to the surface.
We expect that many of Valley Water’s percolation ponds in Santa Clara County will remain filled with water through the end of 2025. The North County percolation ponds currently in operation include:
- Dr. Robert W. Gross Ponds, Piedmont Ponds, and City Park Pond in East San José
- Oka, McGlincy, Camden, Budd, Page and Sunnyoaks ponds in Campbell
- McClellan Ponds in Cupertino
- Kooser Ponds, Los Capitancillos Ponds, Alamitos Ponds and Guadalupe Ponds in South San José
Valley Water focuses on replenishing groundwater in South County, where residents and farmers rely almost entirely on it for their water supply. Valley Water continues to maximize groundwater recharge in South County in the following percolation pond systems in Morgan Hill:
- Madrone Channel
- Main Avenue Ponds
- San Pedro Ponds
Valley Water scientists and engineers continuously assess water supplies and monitor water levels in the aquifers. We will refill more recharge ponds when groundwater conditions require.
We will continue to carefully manage our precious water supplies to ensure safe, clean water for the community. Remember, every drop saved is water that can be used in the future. For more information about our conservation rebates and programs, visit watersavings.org
Nice piece. There are two other points about Valley Water percolation ponds that members of the public should be aware of: