Niles Cone Groundwater Basin

The Supply

Local runoff from the Alameda Creek watershed accounts for about 40% of our total water supply and is used to recharge the aquifers of the Niles Cone Groundwater Basin. This runoff, together with water released from the South Bay Aqueduct at a location east of the town of Sunol, flows down Alameda Creek and into the Alameda Creek Flood Control Channel. Here, the water is captured behind three large, inflatable rubber dams. These dams divert water to the Quarry Lakes where water percolates to recharge the underlying groundwater basin.

About sixteen wells are used to extract water from the groundwater basin. Together, these wells are capable of producing up to 47.5 million gallons of water per day. This water is blended with San Francisco Regional Water System supplies before being delivered to customers.

Groundwater Monitoring

The continued protection and enhancement of the Niles Cone Groundwater Basin is vital to ACWD's ability to continue to meet the water supply needs of the people it serves. Consequently, the basin has been the object of vigorous conservation activities on the part of the District. These activities have included an extensive monitoring program to determine the location and movement of saltwater that has intruded into a portion of the groundwater basin.