A Usable groundwater is enclosed in the aquifers, which are subterranean areas (or the layers) of permeable material (like sand and gravel) that channel the groundwater's flow. The Aquifers can be either confined or unconfined. If a confined aquifer goes after a downward grade from a recharge zone, the groundwater can turn out to be pressurized as it flows. This can form artesian wells that flow freely not including the need of a pump. The top of the upper unconfined aquifer is known as the water table or phreatic surface, where water pressure is equivalent to the atmospheric pressure.