One problem affecting developing countries is lack of water. In African, they have to walk miles just to get a gallon of water. A galloon of water isn't a lot to live off of.
Another is water not being evenly distributed. People build dams on rivers. This means one part of the country gets all the water they want while the other has rationed out water.
Finally, a problem is water pollution. In most countries, there is no sewage system and people have to use to bathroom on the streets or in rivers. There isn't a state-of-the art cleansing system and the water is either wasted or sadly has to be used.
Good luck!