BY NORMAN ROZEFF
The construction of a number of major dams and reservoirs on the Rio Grande and its tributaries has removed the likelihood that the river will ever be as ferocious as it once was through much of its long history.
Amistad Dam near the city of Del Rio, Texas, is 574 miles upstream from the river’s mouth. The Amistad reservoir covers 65,000 acres, and of the reservoir’s 5,535,000-acre-foot capacity, 61 percent is dedicated to water conservation and sediment control. About 56.2 percent of the water released from Amistad Dam is allocated to the United States, and 43.8 percent to Mexico.
In periods of water conservation more water is stored here than at downriver Falcon Reservoir because of its lower evaporation ation rate.
Falcon Dam is an earthen embankment. The dam was dedicated on 19 October 1953 and work was officially complete on 8 April 1954. By October 1954, the dam’s hydroelectric power station began to produce electricity.
President Dwight Eisenhauer came to the LRGV to help dedicate this dam. It has a volume of 2,645,646 acre feet and a surface area of 87,400 acres.
Anzalduas Dam, named after a family that lived nearby in the 1950s, is a diversion dam located in Hidalgo County, Texas, approximately 11 river miles upstream of Hidalgo, Texas, and Reynosa, Tamaulipas. Construction of this dam began in April 1956 and became operational in April 1960.
The purpose of Anzalduas Dam is to divert the U.S. Share of floodwaters to it’s interior floodway. It also enables the diversion of waters to Mexico’s main irrigation canal.
Less significant but vastly important for the river’s water quality was the creation of the El Murillo Drain Diversion Canal. About eight miles upstream of Anzalduas was a high salinity drain coming from Mexican farmland irrigation waters.
In 1966 an international plan was worked out involving financing and project plans. In 1969 the project with its pumps and 75 miles of canal came to fruition. Salt and boron in the river waters was greatly reduced.
Retamal Dam is a diversion dam located 16 miles southeast of the City of McAllen, Texas. Construction on the Mexican portion of this dam began in November of 1971, and the U.S. portion was completed in May 1975. This diversion dam serves two flood control purposes. It enables Mexico to divert it’s share of floodwaters to it’s interior floodway and it also limits flood flows at Brownsville-Matamoros to the safe capacity of the Rio Grande.
On the Pecos River is the Red Bluff Dam and Reservoir. Very much less influential in the flows of the lower Rio Grande are the International Dam and Reservoir and the American Diversion Dam and Reservoir.
In recent years Mexico has constructed a number of dams on Rio Grande tributaries. One major one on the San Juan River is the Marte R. Gómez Dam with its sizable reservoir. On the Rio Alamo is the Las Blancas Dam. On a tributary to the Rio Salado is the Presa Venustiano Carranza (dam and reservoir) (Coahuila). On the Rio San Rodrigo (Coahuila) is the Fragua Dam and Reservoir. On a tributary of the Rio Conchos is the Franciso I. Madero Dam and Reservoir, also the Boqilla Dam and Toronto Lake (Chihuahua). On the Rio Conchos itself is the El Granero Dam (Luis L. Leon Dam) and El Granero Reservoir.
First proposed in the 1980s was the Brownsville Weir and Reservoir. This structure would be constructed below Brownsville on the river.
Its purpose would be to retain the occasional river floodwaters that now simply flow into the Gulf. The conserved waters could have multiple uses including irrigation and recreation. Objections to the construction of such a weir include raising water tables and possibly salinity levels in Mexico. Then some conservationists are critical of any ecological changes to the current status of the mouth of the river.
They fail to realize that the current construct at the mouth is totally man-made. In the last century dams and flood control structures built on the river and its tributaries have sharply curtailed the water exiting at the river’s mouth. When the river was untamed, flood waters would periodically sweep out the silt buildup at the mouth. After flooding, reports often noted a brown stream extending into the Gulf for up to three miles. The river’s mouth therefore was unstable and in constant change.
The building of a weir would likely stabilize the current ecology of the mouth.
In this series I have dealt mostly with the physical nature of the river. A Pulitzer Prize-winning book, “Great River, The Rio Grande in North American History” by Paul Horgan is the definitive work on the river and its people. In Volume I he begins the history of Native Americans then goes into with the colonization of New Mexico by Spanish soldiers and clerics and ends in the Mexican Revolution period of the 1910s.
The most comprehensive book of river’s transportation history is Pat Kelley’s “River of Lost Dreams, Navigation on the Rio Grande”.
The book published in 2010 titled “El Valle: the Rio Grande Delta” with a narrative by Lawrence Lof and astounding photos by Seth Patterson is a fitting conclusion to the river as it exists today.