How relevant is the problem of clean fresh water? a) for the world as a whole, b) for the countries of Tropical Africa

A) For the world as a whole, this is very important because the number of people is growing, a lot of toxic waste from enterprises appears and the water is polluted and perhaps in a couple of decades there will be little clean water relative to the number of people
B) For countries in tropical Africa, this is relevant because problems with clean water cause drought.