The largest use of ground water is to irrigate crops. Ground water can be obtained by drilling or digging wells . A well is usually a pipe in the ground that fills with ground water. This water can then be brought to the land surface by a pump. Shallow wells may go dry if the water table falls below the bottom of the well, as illustrated below.
Water leaving an aquifer is called discharge water.
Water that is pumped from a well is discharge water. Ground water might also discharge naturally as springs or into swamps, lakes, or rivers. Some wells, called artesian wells , do not need a pump. These wells are drilled into an artesian aquifer which is sandwiched between two impermeable layers. Water enters an artesian aquifer in a permeable recharge zone which can be miles away from the well.