This water then evaporates into the atmosphere, condenses and becomes precipitation , thus completing the water cycle. The Occurrence of Groundwater Water can be found beneath the ground almost everywhere. About 97 percent of the world's fresh water is groundwater. The quality and amount of groundwater that is available varies from place to place. Major reservoirs of groundwater are referred to as aquifers .
Aquifers occur in two types of geologic formations.
Consolidated formations are those composed of solid rock with groundwater found in the cracks. The amount of groundwater in a consolidated formation depends on how many cracks there are and the size of the cracks. For example, consolidated limestone formations often contain caverns with much water in them. Unconsolidated formations are composed of sand and gravel, cobblestones or loose earth or soil material. The amount of groundwater in an unconsolidated formation varies depending on how closely packed the solid materials are and how finely grained they are.