� Liba Taylor/Panos Pictures

The Nile at Aswan, Egypt.

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Evaporation of Lake Nasser
After the construction of the Aswan High Dam, Lake Nasser behind the dam was filled by 1978. If it was in the UK, this vast reservoir would stretch from London to Newcastle. However, up to 10% of its water is lost through evaporation each year. The Egyptian government is sufficiently worried about this loss of water that they are considering storing more water in reservoirs in the highlands of neighbouring Ethiopia instead where evaporation is less of a problem. There are also concerns about the silt trapped behind the dam. Although the fishing industry in Lake Nasser is booming thanks to the nutrient-rich water, the rising level of silt may push the water higher, causing it to overflow. The gloomiest prediction is that the weight of the silt could weaken the foundations of the dam, causing it to collapse completely.

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