The cause seems to be human rainforest destruction, an area the size of Texas has been stripped of trees, and climate change that seems to be evolving parts of the rainforest into a savanna habitat.
Ethiopia wants to develop her share of the river, a notion that terrifies Egypt. The fact is there is not enough water in the longest river on earth to serve all the humans who need it. There is the very real threat that the future will see wars fought over Nile River water.
end of the century the ice fields feeding the Ganges will have disappeared. This could reduce the flow of the river by two-thirds.
While this will leave one-third of India's population short of water the effect on Bangladesh will be substantially worse. Reducing the flow of the river will cause brackish water intrusion on the freshwater delta. Add in a rise in sea levels and this nation of 160 million is endanger of disappearing from the face of the earth.