Each year, about 6 million acre-feet of Colorado River water is regulated at Imperial Diversion Dam, just north of Yuma, Arizona, for irrigation and other uses in California, Arizona and Mexico. That water must be released from storage in Lake Mead, nearly 300 miles to the north. It takes about five days for water released from Lake Mead to reach Imperial Dam.
By the time the water arrives at Imperial Dam, the water users that scheduled the water delivery may be unable to take it due to factors that limit those water users’ ability to utilize the water (such as the occurrence of precipitation during those 5 days for agricultural water users). In order to address this requested water that otherwise would be lost to the system, the United States Bureau of Reclamation (USBR) coordinated the construction of Brock Reservoir.
Brock Reservoir is a man-made reservoir, composed of two basins, with a total combined capacity of 7,945 AF. This project was approved and constructed during the period of 2008-2010, with a total cost of $172 million, and was partially financed by CAP, Southern Nevada Water Authority (SNWA), and Metropolitan Water District (MWD) of Southern California; each with an equal contribution of $28.6 million. According to USBR, it is estimated that the project could save 70,000 AF per year. As part of their contribution, SNWA can use 400,000 AF of Intentionally Created Surplus (ICS) water credits over 20 years, while CAP and MWD can each use 100,000 AF of ICS water credits starting in 2016.