Brock Reservoir



The Warren H. Brock Reservoir is a United States Bureau of Reclamation facility that is located adjacent to the All-American Canal 25 miles west of Yuma, Arizona. Often water users on the lower Colorado River cannot fully utilize the water arriving at Imperial Dam causing excess flows to Mexico. Unexpected canal outages, weather conditions and high run-off into the river are a few of the reasons for excess flows diverted to Mexico. These unexpected changes coupled with limited storage near the Imperial Dam and a 4-day water transit time from Lake Mead lead the Bureau of Reclamation to guide the construction and financing of the Warren H. Brock Reservoir. The reservoir was constructed primarily to reduce excess flows to Mexico and provide storage of at least 70,000 acre-feet of excess water each year, but has also created operational flexibility in the lower Colorado River region.

The old Brock Research Center was selected as the best location for a river storage reservoir because of its location along the All-American Canal and ability to flow completely by gravity. The Brock Research Center grew a variety of crops on about 500 acres of farm land between the years of 1940s and late 1990s. Water was diverted from the All-American Canal above AAC Drop 2 before the land was reverted back to the Bureau of Reclamation.

The Brock Reservoir project cost over $172 million. Southern Nevada Water Authority contributed $115 million in return for 400,000 acre feet, which can be taken from Lake Mead at a maximum rate of 40,000 acre-feet a year until 2036. The Metropolitan Water District and the Central Arizona Project each contributed $28.6 million to the Brock Reservoir project. Both will receive 100,000 acre feet of Lake Mead water that can be taken between the years of 2016 and 2036, at a maximum rate of 65,000 acre-feet per year.

Construction began in October 2008 and was completed in September 2010. Seven million cubic yards of soil was removed to create the two 4,000 acre-feet storage cells and then covered with 1,800 rolls of geo-membrane lining and 9 inches of soil cement.

In order to assure maximum flow to the Brock Reservoir, a 6.5 mile lined canal was constructed to carry inlet water from 3 gates located at AAC Drop 1. Outlet water from the Brock Reservoir follows a ¼ mile outlet channel which is pipelined under the Interstate 8 highway and returns to the All-American Canal below AAC Drop 2.


The All-American Canal is used as the conduit for excess flows to the Brock Reservoir. When there are excess flows, the Yuma Area Office will direct the operators at Imperial Dam to divert the excess flows to the Brock Reservoir. The Imperial Dam operators will notify the IID Dispatching Unit that excess flows are being released into the All-American Canal. When the excess flow arrives at the AAC Brock inlet gates, is diverted into the Brock Reservoir inlet canal and flow to the Brock Reservoir storage cells.

When there’s a shortage of flow at Imperial Dam, the Yuma Area Office directs the Imperial Dam operators to reduce the flow into the All-American Canal to manage the shortage. The Imperial Dam the IID Dispatching Unit of the All-American Canal flow reduction and when the decrease arrives at the AAC Brock Reservoir outlet channel, the outlet gates are opened and reservoir storage is used to make up for the water reduction from the Imperial Dam.

The IID Dispatching Unit has the direct SCADA control of the Brock Reservoir. However, the Reservoir is operated under the direction of the Yuma Area Office (USBR).

Surface Area 485 acres
Maximum Depth 22 feet
Inlet/Outlet Capacity 1,800 c.f.s
Cell 1 Storage Capacity 4,000 acre feet
Cell 2 Storage Capacity 4,000 acre feet
Total Capacity 8,000 acre feet
Brock Reservoir Summary Report [PDF] Updated 3/2015