The Cerro de Oro Dam ( en, Gold Hill Dam), also called the Miguel de la Madrid Hurtado Dam, is on the

Santo Domingo River Santo Domingo River is a river of Venezuela. It is part of the Orinoco River basin. See also *List of rivers of Venezuela This is a list of rivers in Venezuela. By drainage basin This list is arranged by drainage basin, with respective tributa ...

in the San Juan Bautista Tuxtepec municipality of the Papaloapan Region of

Oaxaca ) , population_note = , population_rank = 10th , timezone1 = CST , utc_offset1 = −6 , timezone1_DST = CDT , utc_offset1_DST = −5 , postal_code_type = Postal ...

state in southern

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...

. The dam operates in conjunction with the

Miguel Alemán Dam The Miguel Alemán Dam is on the Tonto River in the Papaloapan Region of Oaxaca state in southern Mexico, just upstream from the town of Temascal or Nuevo Soyaltepec, forming the Miguel Alemán Lake with an area of 47,800 hectares. The dam oper ...

, located on the

Tonto River The Tonto River is a river of Oaxaca, Mexico that flows from the mountains of Zongolica. It is dammed by the Miguel Alemán Dam near the town of Temascal or Nuevo Soyaltepec, forming the Miguel Alemán Lake. Below the dam, the river flows southe ...

to control floods in the

Papaloapan The Papaloapan River () is one of the main rivers of the Political divisions of Mexico, Mexican state of Veracruz (state), Veracruz. Its name comes from the Nahuatl ''papaloapan'' meaning "river of the Butterfly, butterflies". In 1517, Juan de Gri ...

basin in

Veracruz Veracruz (), formally Veracruz de Ignacio de la Llave (), officially the Free and Sovereign State of Veracruz de Ignacio de la Llave ( es, Estado Libre y Soberano de Veracruz de Ignacio de la Llave), is one of the 31 states which, along with Me ...

state. Construction began in 1973 and the dam was completed in May 1989. About 26,000 people were displaced by the project. Water quality in the reservoir is poor and deteriorating, affecting fish catches.

Purpose

The Santo Domingo joins the Valle Nacional River below the dam to form the Papaloapan river, which is joined by the Tonto river to the north of the city of San Juan Bautista Tuxtepec and meanders northeastward through the

coastal plain to the

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United S ...

. The Papaloapan river basin was subject to frequent flooding, with the damage sometimes compounded by cyclones. A particularly severe flood in September 1944 covered 470,000 hectares, with great loss of life and property. The Miguel Aleman dam reduced the problem, but further floods occurred after it had been completed in 1955. A flood in 1958 covered 195,000 hectares and one in 1969 covered 340,000 hectares. Meanwhile, the drainage capacity of the Papaloapan river was being reduced by silt carried by the Santo Domingo river. The Papaloapan river Commission recommended building the Cerro de Oro dam on the Santo Domingo river, which would reduce the extent of floods to a manageable level. The combined reservoir of the two dams would also support increased power generation from the Miguel Alemán dam.

Structure

The dam curtain is a massive structure of packed earth and gravel. The reservoir covers 22,000 hectares, joined by a channel to the 47,800 hectare reservoir formed by the Miguel Alemán, giving a combined capacity of 13,380 million m³. There are plans to add hydroelectric generation capacity to the dam, delivering about 10.8 megawatts.

Displaced population

Approximately 26,000 local people were forced to move. The original plan had been to move the people to the area immediately below the dam, but this was frustrated by large landowners in the target region. The move, mostly of Chinantec people, took place in two stages, ending up in 30 new villages in the Uxpanapa region of south-central

. The government bulldozed and burned large areas of the northern Selva Zoque forest to allow for farming in the new settlements, with mixed results. The displaced people later complained that the government had not met its promises in the amount of land allocated. The government denied making such promises, and stated that the people had not owned the flooded land since time immemorial and therefore were not entitled to compensation, although land had been provided.

Environmental issues

The reservoir waters have been changing from oligotrophic to eutrophic due to increased release of nutrients from submerged organic matter, combined with thermal stratification, making them less hospitable to many fish species. Land clearance around the reservoirs has caused increasing silting, and human activities have caused pollution from sewage, trash, fertilizers and pesticides. The dams have also affected populations of some species of fish and crustaceans in the tributary rivers by disrupting their migration patterns.

References

{{reflist Dams in Mexico Buildings and structures in Oaxaca Dams completed in 1989 Papaloapan River