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Floods should prompt dam rethink

Behind the natural flood disaster that has swamped central Mozambique and threatens far more damage is a human failure of management and coordination between the dams along the Zambezi river, according to a regional water expert.

The giant Kariba dam in Zambia and Mozambique's Cahora Bassa "do not talk to each other", Brian Davies at the University of Cape Town told IRIN on Thursday. They have failed to scientifically manage the flow of water along the 258 km stretch of the Zambezi that could have helped avert the current crisis in which both dams are full, and are now being forced to discharge water into an already flooded river system.

"There is no flow management. The dams have operated at minimal discharge on the mythical understanding that the more water there is in the dam the more money there is in the bank through the generation of hydro-power," said Davies, who worked on the initial ecological assessment of Cahora Bassa 25 years ago. "The people of Mozambique are at the butt end of this dreadfully managed system."

What is needed instead is a coordinated Zambezi river basin scheme that would allow dam engineers to release water ahead of the wet season, to leave enough room in the reservoirs to cope with increased water levels during the rains, Davies said. In the current crisis, Kariba is at peak capacity of 85 billion mt of water and Cahora Bassa at 63 billion mt. An accident such as a wall crack or a cascade of water over the lip of the reservoirs due to the intense pressure on the ageing dams would have "catastrophic" consequences, the ecologist warned.

The Zambezi river basin in Mozambique is a naturally occurring flood plain. In the past, human habitation patterns took flooding into account. When the waters subsided, people would move in to plant in the rich soils, and shift to higher ground when the floods returned, Davies said. But the construction of Cahora Bassa has meant that communities have settled much closer to the river.

Managed water releases ahead of the January to March rains would have an impact on settlements along the Zambezi, Davies acknowledged. "People will have to start changing their patterns of living. I know it is a difficult decision to take and would require enormous infrastructural aid," he said. But "one of these days there will be a cyclonic event" that the full dams would be unable to cope with.

"The route to go is to develop a communication strategy using present technology to, in tandem, draw down dam levels and plan for upstream flooding. That's what SADC (the Southern African Development Community) should be doing." Davies added: "Once the (current) aid programme has rescued these people in central Mozambique we need capacity building for a Zambezi river basin plan, that bangs engineers' heads together."


This article was produced by IRIN News while it was part of the United Nations Office for the Coordination of Humanitarian Affairs. Please send queries on copyright or liability to the UN. For more information: https://shop.un.org/rights-permissions

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