Jul 012013
 

The El Macayo dam on the border of Tabasco and Chiapas states in southern Mexico was officially inaugurated last month. The 90-million-dollar dam, which has been under construction for a decade, is designed to regulate flow along the River Grijalva (aka Mexcalapa and Carrizal) that flows through the city of Villahermosa in Tabasco.

Presa El Macayo (Chiapas/Tabasco)

Presa El Macayo (Chiapas/Tabasco)

The city and surrounding settlements have suffered severe flooding many times in recent years, and the El Macayo dam should bring some much-needed relief to around 700,000 people who live in the areas of greatest risk..

Villahermosa floods 2007

A flooded district of Villahermosa, the capital of Tabasco state in 2007. Photo: AFP

Why does the state of Tabasco have a high risk of floods?

The Grijalva–Usumacinta river system is one of the world’s largest in terms of volume. It is easily the river system with the greatest flow in Mexico. It is essentially a double river, with two branches of similar length which both start in Guatemala. Each branch flows about 750 km (465 mi) through Chiapas before they unite in Tabasco about 25 km from the Gulf of Mexico. Each of the two branches has a flow of about 14% of Mexico’s total. The flow of the combined Grijalva–Usumacinta River is about twice that of the Missouri River in the USA.

The state of Tabasco itself receives an average rainfall three times higher than Mexico’s national average rainfall, and accounts for 38% of the country’s freshwater.

Given these conditions, it is not surprising that the state of Tabasco is one of the most vulnerable states for flooding in Mexico. The UN’s Economic Commission for Latin America and the Caribbean has estimated that the state suffered around $4.5 billion in losses from flooding between 2007 and 2011.

Integrated Hydrology Plan

The dam is only one small component in an Integrated Hydrology Plan that is has been designed by the National Water Commission, Conagua. The agency has been assigned more than $110 million this year to complete existing hydrology-related infrastructure projects and update flood protection plans. The previous government spent $640 million to begin a flood management program for the state; this included building flood prevention infrastructure, dredging the major rivers and constructing flood-alleviation channels.

Arturo Núñez, governor of Tabasco state, says that the state’s flood management program should include the relocation of residents currently living in the most vulnerable areas, as well as reforestation of the drainage basins, continued regular dredging of the main rivers, and a reorganization of irrigation systems.

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