Groundwater (or ground water) is the water present beneath Earth 's surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water.The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table.Groundwater is recharged from, and eventually flows to, the surface naturally; natural discharge often occurs at springs and seeps, and can form oases or wetlands.Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells.he upper level of this saturated layer of an unconfined aquifer is called the water table or phreatic surface. Below the water table, where in general all pore spaces are saturated with water, is the phreatic zone. Substrate with low porosity that permits limited transmission of groundwater is known as an aquitard.