Bureau of Reclamation Banner
San Luis Valley Project
Needs a description
Project Links
Project History
Project Data
Contact Information
Related Facilities
Related Documents
San Luis Valley Project (53 KB) (pdf)
General Description| Plan| Development| Benefits


General Description

The San Luis Valley Project is in the south-central portion of Colorado. The authorized project includes the Conejos Division, which regulates the water supply for 80,600 acres of land irrigated in the Conejos Water Conservancy District, and the Closed Basin Division, which will salvage shallow ground water now being lost to evapotranspiration in the Closed Basin of San Luis Valley. The water will be delivered to the Rio Grande for beneficial use in accordance with the Rio Grande Compact among the States of Colorado, New Mexico, and Texas, and the Treaty of 1906 with the Republic of Mexico. A small amount of water will be made available to the Alamosa National Wildlife Refuge. The Conejos Division included the construction of Platoro Dam and Reservoir, which was completed in 1951. The Closed Basin Division is now under construction.

Return to top


Platoro Dam stores floodwaters of the Conejos River, a tributary of the Rio Grande, for release when the normal flow falls below irrigation requirements. The plan includes no diversion or distribution works because the existing facilities of the district are adequate.

The Closed Basin Division facilities will deliver into the Rio Grande that water now being lost to evapotranspiration within the Closed Basin.

Facility Descriptions

Platoro Dam

Platoro Dam is on the Conejos River about 1 mile above the town of Platoro, Colorado. It is an earthfill structure consisting of a main embankment and a dike section, separated by a rock knoll in which the spillway is excavated. The maximum embankment height is 165 feet, and the dam contains 912,000 cubic yards of material. The reservoir formed by the dam has a capacity of 59,570 acre-feet, 6,060 acre-feet of which are for flood control and 53,510 acre-feet for joint use. The spillway is an open rock cut with a concrete control section having a capacity of 3,000 cubic feet per second. The outlet works, with a capacity of 1,000 cubic feet per second, is located in the right abutment.

Closed Basin Division

The Closed Basin Division is now in the construction stage. The plan for development provides for installation of a system of wells, pumping plants, laterals, and a canal to salvage ground water within the Closed Basin for delivery to the Rio Grande. The plan further provides for the preservation and enhancement of existing wildlife habitat and provides desirable fishing and recreation benefits. The plan also includes maintenance of an essentially constant storage level in San Luis Lake and construction of basic recreation facilities.

Operating Agencies

Platoro Dam and Reservoir is operated and maintained by the Bureau of Reclamation. The authorizing act provides that the Secretary of the Interior is authorized to operate and maintain the Closed Basin Division.

Return to top



The early settlers in the area, recognizing the necessity for irrigation to sustain agriculture, began to tap the rivers and creeks by means of small canals and ditches. The first priority for diversion of water from the Conejos River, dated March 1, 1855, was granted to Irrigation District No. 1, which built and operated the Guadalupe Main Ditch. Agricultural development of the county and of the project area received its greatest impetus with the arrival of a group of settlers in 1878. This group and those following began the construction of canals and the establishment of towns and villages. The canals and ditches constructed in the project area were generally community enterprises, each obtaining water by direct diversion from the Conejos River without storage to satisfy late season requirements. As is common in most irrigation areas not having storage facilities, the result has been peak diversion in the spring and early summer months and critical shortages in late season. With this condition limiting the crops, together with the availability of public grazing lands and native meadows, land use closely related to the livestock industry evolved.

After 1880, large canal construction increased rapidly, and by 1900 the greatest practicable amount of natural streamflow had been diverted. Water users then began to construct water storage facilities on the Rio Grande. Two reservoirs in the Upper Rio Grande watershed were completed in 1913 by private capital. These were the Rio Grande (Farmers Union) and the Santa Maria, with capacities of 51,000 and 43,500 acre-feet, respectively. The Continental Reservoir, on a tributary of the Rio Grande, with a capacity of 27,000 acre-feet, was completed in 1928. La Jara and Terrace Reservoirs on La Jara Creek and Alamosa River were completed in 1910 and 1912, respectively. These have a combined capacity of approximately 31,000 acre-feet. By 1910, a rising water table was causing serious damage to the valley lands. This seeped condition was accelerated by large irrigation diversions. Drainage to reclaim seeped lands began about 1911, and by 1921 eight drainage systems serving about 90,000 acres of land had been constructed. These drainage systems have reclaimed a considerable amount of land in the western area of the Closed Basin, but large areas to the east remain to be reclaimed.


Comprehensive engineering investigations in the San Luis Valley Project were initiated by the Bureau of Reclamation in 1936, which resulted in the authorization of the project.


The project was originally authorized by the Secretary of the Interior on February 1, 1940, under section 9 of the Reclamation Act of 1939. A supplemental finding of feasibility and authorization for Platoro Dam and Reservoir was submitted by the Secretary on March 7, 1949.

The Closed Basin Division was authorized by Public Law 92-514, 92nd Congress, October 20, 1972, (86 Stat. 964).


Construction of Platoro Dam and Reservoir was started in 1949 and completed in 1951. Construction of the Closed Basin Division facilities began on November 25, 1980.

Return to top



The increased water supply is of benefit to about 10,000 people living on the farms and in the six villages of the Conejos River area. Principal crops produced are alfalfa, clover, wheat, oats, barley, potatoes, and vegetables.

Water Salvage

A major impact of the Closed Basin Division will be the improvement the salvaged water supply will make in administration of the Rio Grande Compact and the United States-Republic of Mexico Treaty of 1906. This will benefit all the Rio Grande Compact States and the Ciudad Juarez Valley area of the Republic of Mexico. Some additional benefits may accrue to the agricultural economy of the Middle Rio Grande Project, New Mexico, and the Rio Grande Project, New Mexico-Texas.


Platoro Reservoir is in a beautiful mountain setting at a high elevation. It is an excellent recreation feature for the local people and for tourists who seek relief from the heat during summer months. Excellent fishing and boating are provided by the reservoir during seasons when water is in storage.

The Closed Basin Division facilities will provide a dependable source of water for stabilizing the storage level in San Luis Lake. The lake is well located with reference to the valley population distribution, and for tourists. Appreciable recreation benefits will be provided by the facilities.

Flood Control

Platoro Reservoir has 59,571 acre-feet of reservoir capacity assigned for flood control. The San Luis Project has provided an accumulated $5,721,000 in flood control benefits from 1950 to 1999.

Return to top

Last updated: May 17, 2011