River, lakes, and inland seas store 60,000 cubic miles of fresh water. Although most of fresh water is stored in the 7,000,000 cubic miles of found in glaciers and ice caps. Water goes through a cycle process, which replenishes it's supply of water, this is why we can always supply ourselves. Americans use close to 75 to 80 gallons of water per person a day. Our everyday need of water is taken from surface water and groundwater.
Ground water is found under ground in rock formations called aquifers.
It will take millions of years to form large amounts of them.