Here is one you won't find on many newstands. and here is how it works. The earth has little pockets where underground lakes and rivers exist, or there are large sections of porous sand that are filled with water. It gets there from rainfall and is gently filtered by the many layers of dirt, topsoil, sang, gravel and minerals. It produces fresh water. When you deplete an aquifer, often the weight of the earth collapses causing a sinkhole to where the water should be or subsidence, where the layers of gravel, etc. compressed and the water will never fill those regions again--forever limiting the water there. When you dry out farmland it is game over! welcome dust bowl.