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General Description| Plan| Development| Benefits

 

General Description

The Carlsbad Project is in southeastern New Mexico near Ft. Sumner and Carlsbad. The Carlsbad Project stores water in Santa Rosa (a Corps of Engineers Dam), Sumner, Brantley, and Avalon Dams to provide water for about 25,000 acres within the Carlsbad Irrigation District. Project features include Sumner Dam and Lake Sumner (formerly Alamogordo Dam and Reservoir), McMillan Dam (breached in 1991 and replaced with Brantley Dam, Avalon Dam, and a drainage and distribution system to irrigate 25,055 acres of land in the Carlsbad area.

Located in the Chihuahuan Desert, the Carlsbad Project enjoys a number of sun-drenched days during the 212-day growing season. The project's water supply comes from the Pecos and Black Rivers. The Carlsbad Project was one of the earliest Reclamation projects and is significant as a surviving example of mixed 19th and 20th century technology. Many features of this project are listed on the National Register of Historic Places.

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Plan

The Project provides for regulation and storage of irrigation and flood water in Lake Sumner, and Avalon Reservoir, with diversion of water from Avalon Reservoir into a canal system to irrigate project lands on both sides of the Pecos River near Carlsbad.

Facility Descriptions
McMillan Dam and Reservoir

Rehabilitated in 1908, this zoned earthfill dam was 57 feet high and had a volume of 234,000 cubic yards. The reservoir capacity as built was 82,600 acre-feet but siltation had reduced the active capacity to about 33,600 acre-feet (based on survey of September 1964). The dam was located about 14 miles northwest of Carlsbad. When Reclamation completed Brantley Dam in 1991, Reclamation drained McMillan Reservoir and breached McMillan Dam.

Avalon Dam and Reservoir

In addition to forming a small storage and regulating reservoir, Avalon Dam serves as the diversion dam for the project by diverting water into the Main Canal. The dam is located on the Pecos River 5 miles north of Carlsbad, New Mexico. The dam is a zoned earthfill structure that was constructed by private interests in 1888. The dam washed out in 1893 and, after reconstruction, was washed out again in 1904 by the Pecos River flood. The Reclamation Service rebuilt the dam in 1907. The height of the dam was increased in 1912, and again in 1936. The dam now has a structural height of 60 feet and a volume of 202,000 cubic yards.

The dam now has a structural height of 60 feet and a volume of 202,000 cubic yards. This is an earthfilled structure 1,360 feet long and 53 feet high. There are three spillways and an outlet works.

The original reservoir storage capacity was 7,000 acre-feet; a 1996 resurvey showed a capacity of 4,466 acre-feet at the top of conservation pool.

Sumner Dam and Lake Sumner

Sumner Dam and Lake Sumner are on the Pecos River about 250 river miles north of Carlsbad and about 16 miles northwest of Fort Sumner, New Mexico. The dam is a zoned earthfill structure 164 feet high with a volume of 2,250,000 cubic yards.

The dam was constructed in 1937 with a major modification in 1956 which raised the dam and increased the spillway capacity. The dam is a zoned earthfill structure 164 feet high with a volume of 2,250,000 cubic yards. It is approximately 3,00 feet long, averages 30 feet wide at the crest, and is 164 feet high at the maximum section. The outlet works consist of a combination pressure tunnel and a 10-foot diameter penstock upstream of the gates and two penstocks, 5.5 feet in diameter, downstream. Releases are controlled by two 48-inch diameter jet flow valves, with a capacity up to 1,740 cubic feet per second at the top of the flood control pool. Irrigation releases, up to 100 cubic feet per second, may be made through a 20-inch jet flow valve. Larger releases are made through a service spillway near the west end of the dam. This service spillway is a tainter-gated chute-type structure with three 45-foot openings and an invert elevation at 4,259 feet mean sea level. An emergency spillway in the left abutment consists of a fuse plug type embankment. A 500-foot concrete sill, with a crest elevation of 4,275 feet mean sea level, is covered with earth and rock fill, and forms four individual sections at elevations 4,282, 4,283, 4,284, and 4,285 feet mean sea level. These sections are 130 feet, 130 feet, 118 feet, and 118 feet respectively.

The reservoir has an estimated active conservation capacity of 43,768 acre-feet in 1999. In addition to storage for irrigation, the dam and reservoir provide flood control and recreation benefits. While there is no storage allocated to recreation, there is a minimum pool of 2,500 acre feet. In 1980, a transfer of irrigation storage rights to Santa Rosa Dam (a Corps of Engineers' dam), and Reservoir in Northern New Mexico provided for more flood control storage in Lake Sumner (under direction of the Corps of Engineers).

Irrigation and Drainage System

From the east abutment of Avalon Dam, the Main Canal extends generally south along the Pecos River for about 3 miles below the dam, where it divides into the East Canal and the Southern Main Canal. The East Canal continues for about 6 miles. The Southern Main Canal runs south to the Pecos River, which it crosses about 1 mile northwest of Carlsbad through a concrete aqueduct, and continues in a generally southerly direction for about 21 miles to its terminus at the Black River Supply Ditch about 3 miles northwest of Malaga. The design capacities of the Main, East, and Southern Main Canals are 490,45, and 450 cubic feet per second, respectively.

The Black River Supply Ditch empties into the Black River just above a small concrete diversion dam that supplies water to the Black River Canal. This ditch irrigates lands south of the Black River and west of the Pecos River. Seepage and drainage water from Carlsbad Project lands is returned through a drainage system to the Pecos River. There are 151 miles of laterals, 37 miles of canals, and about 24 miles of drains.

Operating Agencies

Reclamation is responsible for the operation, maintenance, and oversight of the Carlsbad Project. The Carlsbad Irrigation District operates and maintains Sumner and Brantley Dams.

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Development
History

The Spanish started irrigating the land when they settled in the Pecos River Basin around 1600. Irrigation in the early 19th century flourished under the Spanish land grant colonization system and was continued after 1850 by the American settlers. The early irrigation systems were community ditches which diverted the normal flow of the river without the benefit of permanent diversion structures. In 1888, a large ranch was located in the general area of the present Carlsbad Project. The ranch manager initiated the first large-scale irrigation attempt. Since the natural characteristics of the area required a more comprehensive treatment than the enterprise could afford, it failed. For the next 17 years, various private interests attempted to make this project financially profitable, but without success.

During this period, project facilities were built, including McMillan Dam for water storage. Avalon Dam for both storage and diversion, the Main Canal, and a distribution system which irrigated 15,000 acres. Private operation of the project ended in 1904 when a Pecos River flood destroyed the central canal and much of the irrigation system and swept away Avalon Dam. Without water for the land, the project settlers faced complete ruin. Upon their request, in 1905 the Reclamation Service was authorized to purchase the system. Reclamation then began investigations prior to rehabilitating the project.

Investigations

By 1907, the system was repaired and extended to permit the irrigation of approximately 25,000 acres. McMillan Dam was rehabilitated in 1908, but by 1932 silt accumulation had reduced the storage capacity of the reservoir and leakage through gypsum and limestone strata had reduced its effectiveness. As siltation advanced, about 13,000 acres of salt cedars grew in the upper reservoir area. After a careful analysis of all factors involved, it was decided to construct a new reservoir at a different site rather than to attempt correction of the defective conditions at Lake McMillan. Detailed investigations resulted in the selection of Alamagordo Dam, now Sumner Dam, site.

Authorization

The original Carlsbad Project was authorized by the Secretary of the Interior on November 28, 1905. Sumner Dam was authorized for construction by the President on November 6, 1935, initial funds having been approved on August 14, 1935, under the Emergency Relief Appropriations Act of 1935. Section 7, Flood Control Act of August 11, 1939, declared Sumner Dam and Lake Sumner were to be used first for irrigation, then for flood control, river regulation, and other beneficial uses.

Brantley Dam and Reservoir of the Brantley Project was authorized on October 20, 1972, by Public Law 92-514, for the purposes of irrigation, flood control, fish and wildlife, recreation benefits, and to provide protection for Avalon Dam and as a replacement of McMillian Dam which was determined to be unsafe.

Construction

Avalon Dam was rebuilt and the project distribution system repaired and extended by 1907.

Sumner Dam was built during 1936-1937. Sumner Dam was raised 16 feet, the service spillway capacity increased, and an emergency spillway constructed during the 1954-1956 reconstruction.

McMillan Dam was rehabilitated in 1908 and breached in 1991. Sinkholes have been an ongoing problem along the eastern edge of McMillan Reservoir causing extensive water losses. The east dike was extended about 1,600 feet in 1934-1935, and construction of an extended dike 10,700 feet long was initiated in 1954 to cut off additional sinkholes. The dike was extended an additional 1,000 feet in 1968.

In 1967, the Carlsbad Irrigation District entered into a rehabilitation and betterment program with the Bureau of Reclamation for concrete lining and improvement of the irrigation distribution system. This program resulted in concrete lining and improvements to some 79 miles of laterals, which significantly reduced water losses and provided a more efficient delivery of water. The Carlsbad Irrigation District has received an extension of the rehabilitation and betterment program to line another 16 miles of laterals and about 9 miles of canals with concrete.

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Benefits
Irrigation

A long growing season, good soil, favorable markets, and irrigation facilities make intensive diversified farming practices attractive and profitable. Cotton and alfalfa are the principal crops, although wheat, barley, oats, and vegetables are produced in abundance.

Flood Control

Sumner Dam contributes materially to the economy of the area by controlling seasonal floods of the Pecos River. Brantley Dam of the Brantley Project, about 13 miles north of Carlsbad, New Mexico, also provides flood control benefits and also helps project Avalon Dam. Brantley Dam has 335,054 acre-feet capacity assigned to flood control functions.

The Carlsbad Project has provided an accumulated $639,000 in flood control benefits from 1950 to 1999.

Recreation

Lake Sumner is in a semidesert area and furnishes year round recreation benefits. There are camping and picnic grounds, cabin sites, and boat docks with small boats for hire. The reservoir provides good bass and catfish fishing in season.

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Last updated: Apr 18, 2011