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

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

OD255)

stage recorders in the canal immediately downstream of Morelos Dam; and silt sampling
stations in the canal system. Both countries are required to take annual river cross-sections
at various locations.

All-American Canal. Pilot Knob and Siphon Drop Poweq>lants - Construction of the
All-American Canal started in 1934 and was completed in 1940 when the first irrigation
water was delivered through it. It replaced the Alamo Canal which was originally
constructed in 1900 to provide a source of irrigation water to the Imperial Valley. Diversion
of water from the Colorado River into the Alamo Canal was made from a headworks facility
located near Pilot Knob. Several problems were associated in making this diversion,
including the removal of trash and constant dredging to control sediment. In 1905, a major
flood on the Colorado River washed out the Alamo Canal head works, and the Colorado
River partially changed course, flowing into the Salton Sea for nearly 2 years and inundating
approximately 330,000 acres of land in the Imperial Valley. On February 10, 1907, the
Southern Pacific Railroad Company was able to force the Colorado River back into its
natural channel.

The All-American Canal is approximately 80 miles long and provides irrigation water to over
500,000 acres of land in the Imperial Valley, over 78,000 acres in the Coachella Valley,
approximately 15,000 acres in the Reservation Division, and over 40,000 acres in the Valley
Division.

A wasteway was constructed on the All-American Canal at Pilot Knob in 1938, and a power
generation facility was added at Pilot Knob off the All-American Canal in 1961. Both
facilities are located upstream of Morelos Dam. The wasteway was constructed to protect
the All-American Canal and provide a place to discharge excess water back to the Colorado
River, in particular those deriving from sidewash inflows or water user cutbacks in Imperial
Valley. Pilot Knob Powerplant was constructed to allow generation of power from water
deliveries made in satisfaction of the 1944 Treaty with Mexico. Pilot Knob has 55 feet of
hydraulic head and can produce up to 33,000 kW of electricity, which is about twice the
hydraulic head that was available at Siphon Drop Powerplant. This made it economically
feasible to construct Pilot Knob Powerplant under a transferred water agreement with the
Yuma County Water Users' Association.

Currently, if Mexico's order at the NIB, less drainage return flows and sediment control
flows below Imperial Dam, is ereater than 800 cfs, the water is routed through the
Pilot Knob Powerplant to generate power, which then takes away water that would otherwise
have been delivered either below Laguna Dam or through the Siphon Drop Powerplant and
California wasteway near Yuma, Arizona. Prior to 1995, water was not transferred to
Pilot Knob Powerplant until a flow of 1,000 cfs was available for transfer.

Siphon Drop Powerplant was originally constructed in 1926 on the old Yuma Main Canal. It
was developed to generate power from water deliveries made to the Yuma Project through
the Yuma Main Canal until 1941, and from water delivered to the Yuma Project and Mexico

Appendix D - 6