How Much Water is Stored in the Livermore-Amador Valley Groundwater Basin
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 A groundwater basin is like a hidden treasure for the population living above it.  It is estimated that the Livermore-Amador Valley Groundwater Basin contains approximately 280,000 acre-feet of porous space filled with about 225,000 acre-feet of fresh water.  The basin is a treasure because it offers our community a secure reserve water supply.  In the event of a prolonged drought, there is enough stored water to supplement the reduced surface supplies to meet the Valley's needs for seven years.  Currently, the groundwater basin provides at least 15% of our drinking water.   During drought years, it is depended on even more.

Groundwater basins are like a surface water reservoir.  If you take out more water than you put back in, the level in the reservoir drops.  In fact, years ago, excessive use of groundwater resulted in reducing the groundwater volume to a low of 127,000 acre-feet.  In contrast, following heavy rains in 1983, the basin held 267,000 acre-feet of groundwater.  The groundwater basin is "naturally" recharged by precipitation, surface runoff and irrigation.

To augment the natural recharge, Zone 7 currently maintains the basin at about 225,000 acre-feet through artificial stream recharge of the Arroyo del Valle and Arroyo Mocho.  This means that imported surface water, when available, is released into the stretches of these streams where the water can seep into the groundwater basin.