In Santa Clara County , approximately 160,000 acre-feet of groundwater is pumped by local water retailers and private well owners each year (one acre-foot equals approximately 326,000 gallons, the average amount of water used by two families of five in one year. An acre-foot of water would cover one acre one foot deep). Groundwater is used for many beneficial uses, including municipal and domestic use, agriculture, and industrial use. The district proactively manages the local groundwater subbasins to ensure a safe and reliable supply of groundwater is available both now and in the future.
In addition to being an important water supply source, the groundwater subbasins also have vast storage capacity which serves as protection against droughts. This enables the district to store excess water in normal and wet years so it is available during dry years or outages. Although groundwater is replenished naturally through rainfall and other sources, this natural recharge is not sufficient to balance the amount of groundwater withdrawn each year.
The Alamitos groundwater recharge pond.
Groundwater recharge
The district operates and maintains 18 major recharge systems, which consist of both in-stream and off-stream facilities. Local reservoir water and imported water are released in over 30 local creeks for artificial in-stream recharge to the groundwater basin.
In addition, the district releases locally conserved and imported water to 71 off-stream facilities (percolation ponds) which range in size from less than 1 acre to more than 20 acres. Through these streams and percolation ponds, the district recharges the groundwater basin with about 157,000 acre-feet of water each year.
This recharge program helps the district counterbalance pumping, maintain the supply of groundwater, and prevent land subsidence. Historically, as much as 13 feet of non-recoverable land subsidence has occurred in the northern portion of the county, at significant costs to local communities. By importing water and through ongoing recharge and monitoring, the district has effectively halted land subsidence in the county.