Water table is the name given to the level of water in any sponge-like saturated pervious rock below the surface of the ground. The level rises and falls in response to seasons of great or little rainfall. This ground water is the source of supply for perennial streams and springs. It is literally filtered water, since it has to pass through several feet of soil before reaching this low level. Streams supplied entirely from the water table are, therefore, clear at all times. Farm wells must be dug deeper than the lowest level to which the water table ever falls, or they become dry during long continued droughts.