These dams consist of low concrete walls about 3 to 16 feet high, across small rivers that stop flowing during the dry season. Sand from erosion during the wet season will collect behind these walls and act as sponges, storing up to 40% of water which will proof useful to the locals during the dry season. These may sound primitive and low tech to some but I would think this is actually an intelligent way of harvesting water with minimum damages to the environment. A miracle indeed, especially, for nations like Africa.
The article and the video below also mentioned the amount of conservation work to reverse the effects of global warming in Africa compared to loud mouth world leading countries. Trees were planted over the course of 25 years and the effect of increased precipitation is becoming evident with a more productive ecosystem in the making.