Comment Malthus (Score 1) 569
You failed to mention Malthus or cycles of growth & famine. To every biosystem there is a maximum of people it can sustain. It is likely that the villages you talk about have grown until that limit was reached. What happens next is a you described: one resource runs out. But digging deeper wells will only help until those run out too.
What did not happen is that the villagers have adapted to the new situation, or hat they have a brighter future. In the west less then 1% is active in farming, but you forced another generation into farming, which does not have a very bright future without modern practices.
You brought in manpower, which Africa has more then enough of. When you were done, the knowledge your engineers had is leaving the country again. Your African co-workers might have learned something too, but they will want to cash in on that and will likely move into the city.
Foreign aid needs to improve all aspects of life, not just digging a well and call it a day.