Amistad Dam (
Spanish
Spanish might refer to:
* Items from or related to Spain:
**Spaniards are a nation and ethnic group indigenous to Spain
**Spanish language, spoken in Spain and many Latin American countries
**Spanish cuisine
Other places
* Spanish, Ontario, Can ...
: ''Presa la Amistad'') is a major
embankment dam across the
Rio Grande between
Texas,
United States, and
Coahuila
Coahuila (), formally Coahuila de Zaragoza (), officially the Free and Sovereign State of Coahuila de Zaragoza ( es, Estado Libre y Soberano de Coahuila de Zaragoza), is one of the 32 states of Mexico.
Coahuila borders the Mexican states of Nu ...
,
Mexico. Built to provide
irrigation water storage,
flood control, and
hydropower generation, it is the largest dam along the international boundary reach of the Rio Grande.
The dam is over long, lies mostly on the Mexican side of the border, and forms
Amistad Reservoir. It supplies water for irrigation in the
Rio Grande Valley, upstream of the Rio Grande's mouth on the
Gulf of Mexico at
Brownsville, Texas
Brownsville () is a city in Cameron County in the U.S. state of Texas. It is on the western Gulf Coast in South Texas, adjacent to the border with Matamoros, Mexico. The city covers , and has a population of 186,738 as of the 2020 census. It ...
/
Matamoros, Tamaulipas
Matamoros, officially known as Heroica Matamoros, is a city in the northeastern Mexican state of Tamaulipas, and the municipal seat of the homonymous municipality. It is on the southern bank of the Rio Grande, directly across the border from ...
.
The dam is owned and operated by the
International Boundary and Water Commission (IBWC), and also facilitates the
Amistad Dam Port of Entry. ''Amistad'' is derived from the
Spanish
Spanish might refer to:
* Items from or related to Spain:
**Spaniards are a nation and ethnic group indigenous to Spain
**Spanish language, spoken in Spain and many Latin American countries
**Spanish cuisine
Other places
* Spanish, Ontario, Can ...
word for "friendship", representing the two nations' cooperation on the dam.
History
Because of the Rio Grande's frequent floods and droughts, the sharing of its water between the US and Mexico has been a contentious issue since the 1800s. The 1906 Treaty for Equitable Distribution of the Waters of the Rio Grande enabled the construction of
Elephant Butte Dam
Elephant Butte Dam or Elephant Butte Dike, originally Engle Dam, is a concrete gravity dam on the Rio Grande near Truth or Consequences, New Mexico. The dam impounds Elephant Butte Reservoir, which is used mainly for agriculture but also provides ...
, the first major Rio Grande dam, in New Mexico. While this benefited water users along the middle Rio Grande, it did little to help the lower Rio Grande Valley, where water flows remained uncontrolled. The 1944
Treaty relating to the utilization of waters of the Colorado and Tijuana Rivers and of the Rio Grande authorized the IBWC to build dams on the uncontrolled border segment of the Rio Grande. The first dam to be completed under the treaty was
Falcon Dam
Falcon Dam ( es, Presa Falcón) is an earthen embankment dam on the Rio Grande between Starr County in the U.S. state of Texas and the city of Nueva Ciudad Guerrero in the Mexican state of Tamaulipas. The dam was built for water conservation, irr ...
in 1953.
[https://cdn.loc.gov/master/pnp/habshaer/tx/tx1100/tx1177/data/tx1177data.pdf ]
After the Rio Grande flooded massively in 1954, with a peak flow of recorded at
Del Rio,
planners realized that a much larger dam would be needed to control the river and two unregulated tributaries, the
Pecos and
Devils Rivers. The proposed site for the larger dam was about a mile (1.6 km) below the confluence of the Devils River and upstream of Del Rio.
During the initial planning stage, it was known as "Diablo Reservoir", a nod to the name of Devils River (''diablo'' meaning "devil" in Spanish). The final design was approved by the two governments as Minute 207, and authorized by an act of
U.S. Congress on July 7, 1960.
Work at the dam site began in August 1963 with foundation drilling and
grout
Grout is a dense fluid which hardens to fill gaps or used as reinforcement in existing structures. Grout is generally a mixture of water, cement and sand, and is employed in pressure grouting, embedding rebar in masonry walls, connecting sect ...
ing in the river bed to support the future concrete section of the dam.
Actual construction of the dam itself began in January 1965 and water was first impounded in 1968.
U.S. president
Richard Nixon and Mexican president
Gustavo Díaz Ordaz
Gustavo Díaz Ordaz Bolaños (; 12 March 1911 – 15 July 1979) was a Mexican politician and member of the Institutional Revolutionary Party (PRI). He served as the President of Mexico from 1964 to 1970.
Díaz Ordaz was born in San Andrés ...
dedicated the dam in 1969.
The construction of the dam required the relocation of of the
Southern Pacific Railroad tracks, of highways, and two bridges.
When the reservoir filled, it inundated ancient rock art left by
Native Americans who once lived in the areas. More than 170 archaeological sites were cataloged during salvage operations between 1958 and 1969, a difficult undertaking due to the arid and remote conditions of the area.
The hydroelectric power plants were added later, with the US plant completed in 1983 and the Mexican plant in 1987. Of the dam's roughly US$125 million cost, the US paid about 57% and Mexico 43%, in accordance with the division of water storage rights in the reservoir.
In 1993, the dam was determined to be silting up at the rate of per year, about 31% greater than had been expected at the time of construction.
Specifications
Dam and spillways
The dam has a total length of , almost 6 miles (10 km), of which are in Mexico and in the United States. The center section at the Rio Grande is a concrete
gravity dam long, with the remainder being earthen embankment. In total, the dam contains 13.5 million cubic yards (10,300,000 m
3) of earth, 1.8 million cubic yards (1,400,000 m
3) of concrete, 1.76 million cubic yards (1,300,000 m
3) of
riprap, and 12,500 tons (11,300 metric tons) of steel. The maximum height above the riverbed is , and the elevation at the dam crest is above sea level.
The roadway along the dam crest is wide.
The embankments are protected on both sides by riprap to reduce
erosion. The riprap is thick on the upstream (reservoir) side and thick on the downstream side.
Because the dam is founded on
karst
Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ...
ic
limestone of the Georgetown formation, a very deep
grout curtain was extended underground to block seepage and the risk of dam failure by internal erosion. Despite this, more than 30 sinkholes have been discovered near the upstream side of the dam and seepage rates have been recorded at over , which may be much higher due to unmeasured seepage on the Mexican side of the dam. However, because the water is traveling through bedrock and not the dam itself, this poses little threat to the dam's structural stability. During extreme flood events, however, this may still be a cause for concern.
Flood waters are released through a concrete ogee crest
spillway
A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure th ...
with 16
tainter gates. The gates measure and can spill up to .
The spillway empties into a stilling basin long, designed to dissipate erosion.
Water supply and flood control
The Amistad reservoir covers at normal (conservation) water levels of above sea level. It is one of the largest lakes in the Rio Grande system by both surface area and volume. Of the reservoir's capacity, 61% is dedicated to water conservation and
sediment control, 32% to flood control, and 7% to surcharge (flood storage above the top of the spillway gates, but below the crest of the dam). At the top of the flood control pool, the reservoir is and at the top of the surcharge pool it is . The lowest lake elevation at which water can be released is , or below normal levels.
At the top of the conservation pool, the reservoir extends up the Rio Grande, up the Devils River, and up the Pecos River. It has a shoreline of , of which are in the US and are in Mexico.
About 56.2% of the water released from Amistad Dam is allocated to the United States, and 43.8% to Mexico. The IBWC determines the fraction of water stored in Amistad Reservoir belonging to either country on a biweekly basis, based on this allocation. The reservoir levels fluctuate greatly due to the region's highly variable annual precipitation as well as heavy water use. The record high level was on September 22, 1974. It reached a record low level of on May 23, 2013, or below normal levels, after several consecutive years of drought.
The average annual inflow to Amistad Reservoir is about . Although the majority – about 70% – of the inflows to Amistad Reservoir comes from the Rio Grande, Devils, and Pecos Rivers, about 30% is from local
spring
Spring(s) may refer to:
Common uses
* Spring (season), a season of the year
* Spring (device), a mechanical device that stores energy
* Spring (hydrology), a natural source of water
* Spring (mathematics), a geometric surface in the shape of a h ...
s. Inflows typically peak between August and October due to
monsoon storms and
hurricane
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
s that strike the Gulf Coast. Flood flows caused by hurricanes are short-lived, but can be extreme,
with a maximum (since dam construction) of more than in late September, 1974.
Dam operators held the outflow from Amistad Dam at about ,
sparing a large part of the Rio Grande Valley from flooding.
Because of diversions of the Rio Grande in the upriver U.S. states of
Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...
and
New Mexico, the
Rio Conchos
The Río Conchos (Conchos River) is a large river in the Mexican state of Chihuahua. It joins the Río Bravo del Norte (known in the United States as the Rio Grande) at the town of Ojinaga, Chihuahua.
Description
The Rio Conchos is the main r ...
(which originates in
Chihuahua Chihuahua may refer to:
Places
* Chihuahua (state), a Mexican state
**Chihuahua (dog), a breed of dog named after the state
**Chihuahua cheese, a type of cheese originating in the state
**Chihuahua City, the capital city of the state
**Chihuahua Mu ...
, Mexico) actually provides the majority of the water flowing from the Rio Grande into the lake. Increasing water use in upriver communities has caused a steady decline in Rio Grande flows throughout the 20th and 21st centuries and has led to concerns about future water levels and supplies at Amistad.
Power generation
The dam has two hydroelectric power stations, one on either side of the border, with a capacity of 66
megawatts (MW) each. The maximum
hydraulic head is , with a minimum of required to run the plants. The four generators have a capacity of 33 MW each and are powered by a 42,300-
hp (31.54-MW)
Francis turbine. The maximum combined water flow through the power plants is .
In 2009, the Amistad Dam plants produced a total of 296,734,000
kilowatt hours.
Border crossing
The Amistad Dam Port of Entry was built when Amistad Dam was completed in 1969. The Dam was a bi-national effort to establish flood control on the Rio Grande and provide sources of water. Although US Department of Transportation statistics combine traffic counts with
Del Rio Texas Port of Entry
The Del Rio Texas Port of Entry is located at the Del Río – Ciudad Acuña International Bridge. A pontoon bridge was first built around 1919, and it was replaced by a more permanent bridge in 1929 built by the Citizens Bridge Company. That b ...
, approximately 65,000 vehicles crossed the dam into the US in 2005.
The border station was rebuilt by the
US Army Corps of Engineers
, colors =
, anniversaries = 16 June (Organization Day)
, battles =
, battles_label = Wars
, website =
, commander1 = ...
in 2012.
Recreation
The dam and reservoir are part of the
Amistad National Recreation Area
Amistad National Recreation Area is a national recreation area managed by National Park Service (NPS) that includes the area around the Amistad Reservoir at the confluence of the Rio Grande, the Devils River, and the Pecos River near Del Rio i ...
.
See also
*
Falcon Dam
Falcon Dam ( es, Presa Falcón) is an earthen embankment dam on the Rio Grande between Starr County in the U.S. state of Texas and the city of Nueva Ciudad Guerrero in the Mexican state of Tamaulipas. The dam was built for water conservation, irr ...
References
Links
Archival film footage of the Amistad Dam and Reservoirfrom the
Texas Archive of the Moving Image
The Texas Archive of the Moving Image (TAMI) is an independent 501(c)(3) organization founded in 2002 by film archivist and University of Texas at Austin professor Caroline Frick, PhD. TAMI's mission is to preserve, study, and exhibit Texas film ...
{{Rio Grande dams and diversions
Dams in Texas
Dams in Mexico
Dams completed in 1969
Dams on the Rio Grande
Hydroelectric power plants in Texas
Hydroelectric power stations in Mexico
1969 establishments in Texas
1969 establishments in Mexico