General Description

The Palo Verde Diversion Project includes the Palo Verde Diversion Dam on the Colorado River, and a spillway and canal headworks to serve the Palo Verde Irrigation District. A levee system and drain were built to protect portions of the Colorado River Indian Reservation. The dam was constructed to replace a temporary rock weir built by the Bureau of Reclamation during World War II. The rock weir was an emergency structure replacing other diversion structures previously built by the Palo Verde Irrigation District.

The Palo Verde Irrigation District is on the west side of the Colorado River in the vicinity of Blythe, California. The district includes about 121,000 acres of valley and mesa lands.

Plan

The diversion dam maintains a constant water surface elevation at the canal intake during periods of normal riverflow. Except during periods of high river discharge, this forebay elevation is maintained at 283.5 feet.

The diversion facilities were designed to discharge 1,800 cubic feet per second into the Palo Verde desilting basin when the river is at the established forebay elevation.

The district diverts its water from the Colorado River on the basis of rights dating back to 1877. The water rights and water supply are adequate for valley lands. Diversion, however, has always been attended by difficulties, primarily those of maintaining satisfactory diversion conditions at the district intake.

The dam, spillway, and canal headworks were built by the Bureau of Reclamation. The canals serving the irrigation district were constructed by private interests.

Unit descriptions and facilities

Palo Verde Diversion Dam

The Palo Verde Diversion Dam, located on the Colorado River 9 miles northeast of Blythe, is a semipervious barrier of sand, gravel, and rockfill , with a crest width of 20 feet, a length of 1,850 feet which includes the spillway, and a maximum height of 46 feet above the streambed. The embankment, consisting of two zones, contains 157,000 cubic yards of material. Both the upstream and downstream slopes of the embankment are 4:1 from crest elevation to riverbed. The upstream zone consists of sand, gravel, and cobble fill, which is protected with 24 inches of riprap to elevation 20.0 feet. The downstream zone is rockfill taken from structure excavation and quarry. The spillway control structure is founded on rock at the right abutment of the dam. It is a gated structure consisting of three 50-foot bays, separated by two 8-foot-thick intermediate piers. The piers and gravity wall abutments support a bridge structure on which is mounted the hoist for operating the spillway radial gates. The headworks structure is designed to direct 1,800 cubic feet per second from the river into the settling basin of the Palo Verde Irrigation District canal system with diversion water at elevation 283.5 feet. The structure includes four 12- by 8-foot conduit barrels with a downstream transition and training channel.

A control house is located immediately upstream of the headworks. In it are housed the panels for the power distribution and control system, forebay stilling wells and probe units, emergency power units, and recording equipment. Emergency power is supplied by a 30-kilowatt, 230-volt, 3-phase, 60-hertz gas engine generator set for use during failure of the local power supply.

Levee System

The 30-mile levee system is divided into the Lower Arizona Levee, Upper Arizona Levee, and the California Levee. At the request of the Tribal Council of the Colorado River Indian Reservation at Parker, Arizona., the levees were located about 1,300 feet from the river channel so the shoreline would not be encroached upon and would, in the future, be made available for recreation development. The tops of the levees were surfaced with 6 inches of selected gravel to provide a roadway for maintenance purposes and access to various points on the river. The design flood for the levees is 75,000 cubic feet per second. The levees are provided with a 20-foot top, land-side slope of 1.5:1, river-side slope of 2:1, and 4 feet of freeboard. The amount of riprap placed varies within different sections of the levees.

Drain

A 21-mile-long intercepting drain was constructed parallel to and 300 feet from the landward side of the lower levee; the outfall is downstream of the dam. The drain was designed for a capacity of 30 cubic feet per second at the upstream end, increasing to 128 cubic feet per second at the outfall below the dam.

Operating agencies

The Palo Verde Diversion Dam and diversion works were turned over to the Palo Verde Irrigation district for operation and maintenance on December 17, 1957. Operation and maintenance of the levees and drain were transferred to the Bureau of Indian Affairs on August 20, 1958.

Development

In the late 1870's, Thomas Blythe secured title to a block of land comprising roughly the northern third of the Palo Verde Valley. Blythe cultivated some land with water that was diverted from the Colorado river by gravity. In 1923, the California State legislature passed a special act creating the Palo Verde Irrigation District. The act combined the duties and functions of the existing levee and drainage districts into one organization and authorized the newly created district to acquire the properties and water rights of the Mutual Water Company.

Investigations

Before the construction of Hoover Dam, the heavy silt load of the Colorado River constituted a serious problem to the district at the diversion point.

With the closure of Hoover Dam early in 1935, diversion conditions at the Palo Verde intake improved considerably. The clear water released from Hoover Dam materially reduced the district's silt problem. However, about two years after closure of Hoover Dam, retrogression of the riverbed started in the vicinity of the Palo Verde intake. By 1942, it had become difficult for the irrigation district to divert water under normal riverflow conditions.

In 1943 and 1944, the problem became serious since it seemed probable that Palo Verde Valley crops might be lost. To temporarily alleviate this problem, one provision of the First Deficiency Appropriations Act, approved April 1, 1944, authorized the Bureau of Reclamation to build a temporary weir for raising the river level to an elevation that would provide satisfactory diversion at the Palo Verde intake.

Construction began immediately after passage of the act, and a temporary rock weir was completed in 1945. Investigations for a permanent structure continued intermittently from 1944 until construction of the permanent works was authorized.

Authorization

The project was authorized by the Congress by the act of August 31, 1954 (68 Stat. 1045).

Construction

Construction began in 1956 on Palo Verde Diversion Dam, levees, and drain. The first water was diverted into the Palo Verde Irrigation District's canal system on October 28, 1957. Construction of the dam was completed on December 17, 1957.

The contract for the construction of the levees and drain was awarded February 2, 1956. The work was completed and accepted by the Government on August 4, 1958.

Benefits

Completion of the Palo Verde Diversion Dam ensured adequate diversion of irrigation water to the fertile and highly productive land in the Palo Verde Irrigation District. The principal crops are alfalfa, sudan grass, cotton, wheat, melons, and miscellaneous vegetables.

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