WSP12636

• File Number: 8282.300
• Description: Colorado River Operations and Accounting - Lower Basin Administrative Procedures
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 8/1/1996
• Author: DOI-BOR
• Title: Description and Assessment of Operations-Maintenance and Sensitive Species of the Lower Colorado River - Volume II - Appendices-Etc - 08-01-96
• Water Supply Pro - Doc Type: Report/Study

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APPENDIX D - MAJOR FACILITIES ON THE WWER COWRADO RIVER

The following section presents a brief description of the major facilities on the lower
Colorado River.

~~una Dam - Construction of Laguna Dam began in July 1905, and the diversion structure
was completed in 1909. Laguna Dam was originally constructed to serve as a diversion
structure and desilting works for the Yuma Main Canal on the California side of the
Colorado River and for the North Gila Canal on the Arizona side of the Colorado River.
The dam raised the water level above the original stream bed approximately 13 feet
(138 to 151 feet msl). The Yuma Main Canal served the Yuma Project which consisted of
the Reservation Division in California and the Valley Division in Arizona. The Yuma
Project was the ftrst Reclamation Project on the lower Colorado River. The dam originally
diverted water to approximately 14,700 acres of land in the Reservation Division, over
53,000 acres in the Valley Division and approximately 3,500 acres in the North Gila Valley.
In 1941 a turnout was constructed on the All-American Canal at Siphon Drop to supply part
of the water for the Yuma Project. In June 1948 the diversion works for the Yuma Main
Canal were sealed at Laguna Dam and all of the water for the Yuma Project was delivered
through the All-American Canal.

Delivery of water to the North Gila Irrigation District through the Gila Gravity Main Canal
was authorized in May of 1953. Diversions into the Gila Gravity Main Canal are made at
Imperial Dam. This ended the need to divert water to North Gila from Laguna Dam, and
the Arizona heading for the North Gila Canal was sealed.

Today Laguna Dam serves as a regulating structure for sluicing flows that control sediment
below Laguna Dam, and to help store excess flows that arrive at Imperial Dam to prevent
over deliveries to Mexico. Water stored behind Laguna Dam can be used to make up part of
Mexico's water order when a shortage of water relative to water user demand arrives at
Imperial Dam. Laguna Dam also protects the downstream toe of Imperial Dam.

Total storage behind Laguna Dam is currently estimated to be 700 acre-feet. Prior to the
1983 Colorado River flood the capacity was approximately 1,500 acre-feet. Dredging was
carried out behind Laguna Dam in the 1950s to the early 1970s, in order to maintain its
relatively small storage capacity. Sediment removed from above Laguna Dam was placed
directly downstream of the rocktill weir in the flood plain.

Laguna Dam passed flpws in excess of 180,000 cfs prior to the construction of Hoover Dam.

Hoover Dam - Hoover Dam was authorized under the Boulder Canyon Project Act in 1928.
The dam was constructed in the Black Canyon of the Colorado River about 36 miles from
Las Vegas, Nevada. Construction started in 1931 and was completed in 1935.

Hoover Dam was constructed to provide storage so a reliable water resource could be

Appendix D - 1