Natural sources of water are rarely safe. When open to nature they can be contaminated with household and industrial waste, animal feces, parasites and waterborne diseases like cholera. They are also unreliable, drying up or running out. This means finding a new source that could be many miles away. A community cannot move every time this happens. It is therefore much better and safer to create a water facility that is local, and uses water that needs only minimal filtering, like groundwater, rainwater, or similar.