Valley Water filling up many percolation ponds across Santa Clara County

The recent series of atmospheric rivers delivered significant rainfall across Santa Clara County. These storms, which started in mid-December and lasted through mid-January, also helped fill local reservoirs and increased the Sierra Nevada snowpack.

While these storms have not pulled us out of drought, they have improved our water supply outlook.

Recently, Valley Water began using a portion of last year’s imported water supplies to fill many of the 102 percolation ponds across the county. These percolation ponds help replenish local groundwater, which supports about 40% of the water used in Santa Clara County. Percolation ponds are water supply facilities built in areas where permeable materials such as gravel and sand allow water to seep into our aquifers. Their primary and most important purpose is to allow water to filter underground to maintain healthy groundwater conditions.

The ponds that are expected to be full or almost full by the end of January and through at least the end of winter include:

  • The Upper Penitencia Creek system of 18 recharge ponds in east San José
  • City Park Pond, owned by the City of San José
  • Los Capitancillos Ponds, a system of 11 ponds near Coleman Road and Almaden Expressway in San José
  • Alamitos Pond and the system of Guadalupe Ponds off Highway 85 and Almaden Expressway in San José
  • The Los Gatos system of recharge ponds in Campbell (25 of 29 ponds)

Valley Water plans to increase our groundwater recharge efforts in mid-February by using imported water from San Luis Reservoir in Merced County. We anticipate filling several ponds in South County, including:

  • A series of 10 ponds in Madrone Channel along Highway 101 in Morgan Hill
  • The Main Avenue and Ponds and one of San Pedro Ponds in Morgan Hill
On Jan. 23, 2023, a view of a partially-filled Alamitos Pond at Valley Water headquarters on Almaden Expressway.

Valley Water is also using some of the rainfall-runoff recently captured in Anderson Reservoir for percolation into Coyote Creek to help recharge the groundwater basin in the Coyote Valley and the Santa Teresa area of south San José. Valley Water is releasing water from Anderson Reservoir this winter to keep water levels within the reservoir at 3.7% of capacity.

While the recent series of storms helped fill local reservoirs, Valley Water has not started diverting the recent rainfall-runoff into most of our percolation ponds. Rainfall-runoff that makes its way into creeks and streams is often filled with sediment and debris that can clog percolation ponds. After the sediments settle in the reservoirs, Valley Water will slowly release the water to creeks throughout the year. Some of that water will be diverted into percolation ponds.

Local groundwater levels have declined due to three years of drought. However, groundwater levels have been increasing recently due to a variety of reasons, including the recent wet weather and conservation by the community. We expect these positive trends to continue over the next several months.

It’s important to note that three incredibly wet weeks do not erase three years of drought. On Jan. 19, the U.S. Drought Monitor still classified all of Santa Clara County as being in moderate drought. We are cautiously optimistic that the significant snowpack levels in the Sierra Nevada will result in increased amounts of water imported from outside the county compared to the past few years.

But even when this drought ends, we know another one will impact us in the future. That’s why it’s important to make water conservation a way of life in Santa Clara County. Valley Water has many programs to help homeowners and businesses save water. For more information,


    1. Valley Water has plans to start filling McClellan Pond in the second half of March and will likely keep supplying it with water through the spring, summer, and October unless conditions change. We didn’t supply the pond with water this winter due to a planned pipeline outage to rehabilitate one of our main pipes.


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