Rock catchment with water storage in reservoir
A rock catchment is a type of ground catchment system whereby a large rocky surface is used as the source of surface runoff which is channeled and stored in either a tank or a dam. Rock catchments are, however, considered as a separate category because they are so different from other ground catchment systems having several distinctive features such as gravity flow supplies. Where suitable sites exist rock catchment dams are one of the cheapest and most effective types of rainwater storage system (granite inselbergs in Africa are ideal locations for rock catchments)
For more information: how to harvest surface runoff through rock catchment