APPENDIX D - MAJOR FACILITIES ON THE LOWER COLORADO RIVER

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

Laguna 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 first 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 rockfill weir in the flood plain.

Laguna Dam passed flows 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 developed for use downstream. Prior to construction of the dam, the Colorado River downstream went through recurring cycles of flooding in the spring and drought during the summer and fall, which caused damage to crops and nearby property. Flows ranged from an estimated maximum of 300,000 cfs on July 8, 1884, to a low of 700 cfs recorded on December 28, 1924, with a recorded average flow of nearly 15,570 cfs prior to the construction of Hoover Dam.

The dam stores water to a maximum conservation pool of about 27 maf at elevation 1,221.4 feet above msl, and backs water upstream approximately 115 miles creating a surface area of about 163,000 acres at elevation 1,229 feet msl. The dam is 726 feet high and the water depth is approximately 590 feet.

The dam is a major source of power generation in the Southwest, and also provides protection to the downstream area from floods and drought. Water stored in Lake Mead provides a source of water for the lower basin States should a drought occur, although sediment accumulation in the upper end of the reservoir is gradually decreasing the water storage capacity. The powerplant generating capacity is approximately 2,080,000 kW with maximum release at approximately 49,000 cfs. The spillways have a maximum release capacity of about 400,000 cfs at 1,232 msl with the drum gates in a closed position. This provides a total release capacity of 449,000 cfs. Flood storage of 1.5 maf is located between elevation 1,219.6 and 1,229 msl.

Imperial Dam

Imperial Dam is located approximately 18 miles northeast of Yuma, Arizona. Construction of Imperial Dam and Desilting works by Reclamation began in January 1936 and was completed in July 1938. The dam was constructed to provide a diversion of Colorado River water to the Imperial and Coachella Valleys, the Reservation Division, and Yuma Valley through the All-American Canal on the west side of the dam; and to the Gila Project and the Yuma Auxiliary Project through the Gila Gravity Main Canal on the east side of the dam.

Imperial Dam, which raised the water surface above the original river 23 feet to elevation 181 feet msl, was designed to provide a maximum diversion of 15,155 cfs for the All-American Canal; 2,200 cfs for the Gila Gravity Main Canal; and was designed to pass a maximum flood of 180,000 cfs.

Imperial Dam created a reservoir that originally had a capacity of 85,000 acre-feet, but as was anticipated, the reservoir quickly filled with sediment. Intermittent dredging and sluicing operations are required to maintain a small reservoir pool of about 1,000 acre-feet in capacity to ensure diversions can be made to the All-American Canal and Gila Gravity Main Canal. Desilting works were provided for both the All-American Canal and Gila Gravity Main Canal. Sediment accumulations are sluiced downstream to the Laguna Desilting Basin where the sediment is removed by dredging and disposed of adjacent to the desilting basin.

Parker Dam

Parker Dam spans the Colorado River between Arizona and California 17 miles northeast of the town of Parker, Arizona. Constructed between 1934 and 1938 by Reclamation. Parker Dam's primary purpose is to provide reservoir storage from which water can be pumped into the Colorado River aqueduct and the CAP aqueduct. Lake Havasu, the reservoir behind Parker Dam, is about 45 miles long and covers 20,390 acres. It can store 648,000 acre-feet of water. The CAP began pumping water from Lake Havasu in 1985. It has a capacity for delivery to users in central and southern Arizona.

Parker Dam is one of the deepest dams in the world; 73 percent of its structural height of 320 feet is below the original riverbed. About 85 feet of the dam is visible. The dam's superstructure rises another 62 feet above the roadway across the top of the dam. Parker Powerplant is located on the California side of the Colorado River immediately below the dam. It houses four hydroelectric generating units. Each unit can produce 30,000 kW of hydroelectric power. Four 22-foot diameter penstocks carry up to 5,500 cfs each, to feed the generating units. Fifty percent of the plant's power output is reserved for MWD's use to pump water along the Colorado River aqueduct to the Pacific Coast. The remaining power is marketed by WAPA, a DOE agency. Under an agreement between Reclamation and MWD, the latter agency financed essentially the entire cost of constructing Parker Dam. MWD's Whitsett Pumping Plant, 2 miles upstream from the dam on Lake Havasu, lifts water from the reservoir into the Colorado River Aqueduct.

Davis Dam

The Davis Dam and Powerplant facility was constructed by Reclamation in Pyramid Canyon, 67 miles downstream from Hoover Dam. The site is 10 miles north of the point where Arizona, Nevada, and California meet, and approximately 2 miles upstream from Laughlin, Nevada, and Bullhead City, Arizona.

Completed in 1953, Davis Dam is an earth and rock-fill embankment with a concrete spillway, gravity structure, intake structure, and powerplant. The dam's primary purpose is to re-regulate Hoover Dam releases so that they meet downstream demand, including the annual delivery of 1.5 maf of water to Mexico. This is in accordance with the Mexican Water Treaty of 1944.

Located on the Arizona side of the river, the Davis Dam Powerplant is immediately downstream from the dam embankment. Each Davis unit is rated at 50,000 kW. DOE markets all of Davis energy and capacity. The forebay is formed by the intake, spillway, and gravity structures.

Lake Mohave lies behind Davis Dam and is bound for most of its length by the steep walls of Pyramid, Eldorado, and Black Canyons. The lake is relatively narrow, not more than 4 miles across at its widest point, but provides significant recreation opportunities and habitat for fish and wildlife. Additionally, the lake captures and delays flash flood discharge from the side washes below Hoover Dam.

Headgate Rock Dam

Headgate Rock Dam is located on the lower Colorado River about 1 mile northeast of the town of Parker, Arizona, and 14 miles below Parker Dam. It was constructed in 1941 as a diversion structure to provide irrigation water to the CRIT. A 3-unit, low-head powerplant was added to the structure in 1992.

The water retained by the dam is named Lake Moovalya which extends upstream approximately 10 miles and contributes a stable water surface to the recreational area referred to as the Parker Strip. The dam raises the river water level approximately 15 feet but develops no useable storage. The water releases below Headgate Rock Dam mirror the releases from Parker Dam.

The existing spillway capacity through all 7 gates is 140,000 cfs. The maximum powerplant discharge is 20,000 cfs. The maximum generating capacity of the powerplant is 19.5 MW.

Palo Verde Diversion Dam

The Palo Verde Diversion Dam consists of a concrete, gated structure with an adjacent embankment. It was constructed by Reclamation in 1956 and 1957, as a permanent replacement for the old Palo Verde rock weir. The dam raises the water levels approximately 12 feet, which is sufficient for the gravity flow to provide the water supply to the Palo Verde Valley including the city of Blythe. The dam has no useable storage even though the backwater from the dam reflects approximately 15 miles upstream. The dam is operated and maintained by the PVID.

Senator Wash Pumping/Generating Plant and Regulating Reservoir

Senator Wash is a pumped, offstream storage facility located approximately 2 miles upstream from Imperial Dam. It was constructed to supplement limited storage behind Imperial Dam and Laguna Dam. When sufficient storage is not available at Imperial and Laguna Dams, Senator Wash is used to regulate excess flows arriving at Imperial Dam to prevent over deliveries to Mexico, and to ensure demands can be met when flows arriving at Imperial Dam are less than water user demand.

Construction of Senator Wash began in 1964, with operation beginning January 30, 1966. The reservoir has a capacity of 13,836 acre-feet at elevation 251 feet msl. Senator Wash water surface elevation varies between 210 feet and 240 feet (current reservoir restrictions prevent raising the reservoir to elevation 251 feet due to concerns with seepage and high hydraulic pressure under the toe of Senator Wash Dam and along Squaw Lake Dike). The reservoir elevation fluctuates according to water user demand and flows arriving at Imperial Dam.

Glen Canyon Dam

Glen Canyon Dam, which formed Lake Powell, was completed in 1963 as a principle part of the Colorado River Storage Project. It is a concrete, arch dam 710 feet high and 1,560 feet wide. The maximum generating discharge capacity is 33,200 cfs which may be augmented by an additional 15,000 cfs through the river outlet works. The active capacity of Lake Powell is 20,876,000 acre-feet. Lake Powell has no legislated flood control space. The required system flood control space is allocated among selected project reservoirs including Lake Powell, to augment the 1.5 maf required to be available in Lake Mead.

The filling of Lake Powell occurred from 1963 through 1980, during which time all releases of water in the lower Colorado River system were in response to downstream demands and other consumptive uses.

Morelos Dam

Morelos Dam is located approximately 9 miles southwest of Yuma,Arizona. Morelos Dam was constructed by Mexico beginning in late 1948 and was officially operational on November 8, 1950. Its construction was authorized under Article 12 of the Mexican Water Treaty of 1944 to provide a diversion for the delivery of Colorado River water to the Mexicali Valley.

Minute 242 (Minutes are defined as decisions of IBWC and signed by the Mexican and United States commissioners) of IBWC and the Mexican Water Treaty of 1944 provide requirements for deliveries at the NIB and SIB near Yuma and San Luis, Arizona, respectively. Up to 140,000 acre-feet annually of agricultural drainage water can be delivered to Mexico at the SIB. The remaining 1,360,000 acre-feet of water is to be delivered to Mexico at the NIB annually and diverted at Morelos Dam to the Mexicali Valley. For several years after the United States Bypass Drain was completed in 1978, the Colorado River Channel downstream of Morelos Dam was normally dry. Flows below Morelos Dam now occur only when water in excess of Mexico's requirements arrive at the NIB. Recently, however, various wet open areas occur along the channel below Morelos Dam. Apparently scouring into the ground water table has resulted from flood flows which were passed below Morelos Dam several times since 1978. The area now supports extensive stands of riparian woodland vegetation and a number of areas of cattail marsh (Werner pers. comm. 1996)

Water in excess of Mexico's water order at the NIB is normally passed through Morelos Dam, through the Limitrophe Division, and into the original Colorado River Channel downstream. Water in excess of Mexico's water order occurs when surplus or flood releases are made from either the Colorado River system or the Gila River system. Excess water arriving at Mexico may also result from sidewash inflows that occur above or below Imperial Dam; from a sudden drop in water user demand; or when insufficient storage is available in Senator Wash, Imperial or Laguna reservoirs.

Flows arriving at Morelos Dam normally range from about 900 cfs to over 3,000 cfs during the year. During 1983, flows in excess of 40,000 cfs arrived at the NIB due to flood control releases on the Colorado River, and in 1993 flows in excess of 25,000 cfs arrived at the NIB due to flooding on the Gila River.

Mexico is responsible for the operation and maintenance of Morelos Dam and associated expenses. Gaging stations are provided and operated by the United States on the Colorado River at Yuma, at the NIB, 4 miles downstream of the NIB, and at the SIB. The United States provides monthly ground-water elevations for lands in the United States above and below Morelos Dam as well as a silt sampling station at Yuma, Arizona. Mexico is required to provide river gauges immediately upstream and downstream of Morelos Dam; 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 Powerplants

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 headworks, 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 greater 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 ort hrough 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 from 1941 through 1972 through the All-American Canal. The original powerplant was shut down in 1972, and a new powerplant was constructed and placed in operation in 1987. It currently operates to develop power from Yuma Project deliveries and deliveries made to Mexico. If Mexico’s order at the NIB, less drainage return flows and sediment control flows below Imperial Dam, is less than 800 cfs, the water is normally routed through the Siphon Drop Powerplant to generate power. Siphon Drop Powerplant requires a minimum flow of 350 cfs to operate and, to the extent possible, this flow is maintained through delivery requirements to Mexico and water ordered for the Valley Division of the Yuma Project.

The Yuma Main Canal wasteway, more commonly referred to as the California wasteway, was constructed in 1912 at the same time the Colorado River Siphon was constructed under the Colorado River at Yuma, Arizona, to deliver water to the Yuma Valley Division in Arizona. It was constructed to protect the Yuma Main Canal if excess flows are diverted into the canal or sudden cutbacks in water use in the Yuma Valley occur. The wasteway allows those excess flows to be diverted back into the Colorado River. Later, after the All-American Canal was constructed, a portion of the water delivery to Mexico was routed down the All-American Canal through Siphon Drop Powerplant and the Yuma Main Canal wasteway.

The Gila Gravity Main Canal

Construction of the Gila Gravity Main Canal occurred between 1936 to 1939. The canal is 20.5 miles in length with two tunnels and has a capacity of 2,200 cfs. It serves approximately 100,000 acres of farmland located in the WMIDD, the North Gila and South Gila Valleys, the Yuma Mesa Irrigation and Drainage District, and the Unit "B" Auxiliary Project.

The headworks for the Gila Gravity Main Canal are located at Imperial Dam. Since the Gila Project was originally authorized to irrigate 585,000 acres, three diversion outlets were originally provided at Imperial Dam. The acreage to be served by the project was reduced in 1947, so only one outlet and one desilting basin were put into operation.

The water delivery from the Gila Gravity Main Canal to the North Gila Canal started in 1943. Water was first diverted from the Gila Gravity Main Canal to the Wellton-Mohawk Division in 1952, and the last of the Wellton-Mohawk Project was completed in 1957. Water diversions to Yuma Mesa started in 1952 and water diversions to the South Gila Valley began around 1965.

Figure D1. List of owner/operators for major facilities along the lower Colorado River.

FACILITY	OWNER	OPERATOR	POWER PLANT	DIVERSION
Senator Wash	U.S.	IID	pumped storage	none
Laguna	U.S.	IID	none	none
Imperial	U.S.	IID	none	gravity
Palo Verde	U.S.	PVID	none	gravity
Headgate Rock	CRIT	U.S.	low head hydro	gravity
Parker	U.S.	U.S.	hydro	(see note 1)
Davis	U.S.	U.S.	hydro	none
Hoover	U.S.	U.S.	hydro	(see note 2)
Morelos	Mexico	Mexico	none	gravity
Pilot Knob Powerplant	U.S.	IID	low head hydro	none
Siphon Drop Powerplant	U.S.	Yuma Co Wat Users	low head hydro	none

Note 1 - MWD operates the Whitsett pumping plant and CAP operates the Havasu Pumping Plant from the lake behind Parker Dam.

Note 2 - Southern Nevada operates pumped diversion from the lake behind Hoover Dam.

General: During normal years all water released through the dams is discharged through the power plants if so equipped within the capacity of the power plant. Otherwise it is released through discharge gates or valves. No water goes over the dams during normal years. Hoover Dam is equipped with a Pelton wheel generator for system power and startup. All other generators and pumps are turbine type.