Sunday, January 18, 2015

What could be done but probably won't

Africa’s richest natural resources are its rivers and lakes, and over the years, there have been many proposed projects to harness the continent’s immense water resources. One of the most talked-about is the Grand Inga Dam project in the DR Congo, first proposed over 50 years ago. Inga is at the mouth of the Congo river, where an immense drop in elevation plunges the water of the Congo – the world’s second largest by volume, after the Amazon – with so much force that that the hydropower potential generated is enough meet the electricity needs of the whole of sub-Saharan Africa.

Another plan is to channel water from the Oubangi river – one of the Congo river’s main tributaries – to replenish the waters of Lake Chad, which have shrunk by more than 90% over the past 50 years. At 25,000 in 1963, Lake Chad used to be Africa’s fourth largest lake. But higher evaporation rates in the arid Chad region – partly driven by climate change – and increased water withdrawals from feeder rivers for cotton and rice production have put increased demand on the lake, and it has dwindled to just 1,540 The idea to divert part of the Oubangi’s water into Lake Chad was first proposed in 1960s, but began to get international attention more recently. It involves creating a retention dam at Palambo, upstream from the city of Bangui, the capital of Central African Republic. Water from the dam would flow by gravity through a navigable, 1,350 km man-made canal into the Chari-Logone river system, the main feeder of Lake Chad that supplies 95% of its water. This arrangement would check the encroachment of the Sahara desert and act as a much-needed source of water for Sahelian communities – although Lake Chad is subject to much evapotranspiration, it is not saline, and so is one of the few sources of fresh water in the region.

Lake Kivu sits in a volcanic area between Rwanda and the DR Congo, where carbon dioxide and methane from below the earth surface seeps into the lake and lies quietly dissolved under 1,000 feet of water. But an earthquake or a lava flow could loosen the trap and catastrophically release the gases, as happened in Cameroon in 1986, when a deadly cloud of carbon dioxide from Lake Nyos asphyxiated over 1,700 people. Under certain conditions, the newly released methane could even explode as it hits the air. To avert danger, the Rwandan government has launched a grand engineering scheme to suck up explosive methane from depths of 1,000 feet and pipe it to a nearby power plant, generating 25MW of power. The Rwandan government says the KivuWatt project could double the country’s electricity production and reduce its dependence on imported diesel fuel that currently powers a large share of its electricity.

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