Because of the force of gravity, water always moves downslope. Some groundwater reservoirs are like pockets and are trapped by certain types of rocks. Sometimes even the water that is infiltrating into the ground will not be able to reach and refill the pocket of water. These are called confined aquifers . One-third of our drinking water in the US comes from wells.
People drill holes in the earth to reach aquifers and pump water out from a tube called a well .
It is important to keep our aquifers free of polution so that our water is safe to drink.