Groundwater

Groundwater is water which occurs below the solid surface of the earth. The term groundwater usually refers to as subsurface water which occurs in fully saturated soil and rock formations, but may also include water occurring in partially-saturated formations.

Soil and rock formations contain void spaces between individual soil particles and in fractures in rock which water can enter and move through. Water can enter these formations from neighboring saturated formations, from infiltration from surface water flow and precipitation, and from deliberate groundwater recharge.

Naturally-occurring groundwater is about 4% of the total water on the earth, and is about two-thirds of the total fresh water in the world. As a result, it is an important source of drinking and irrigation water in many areas of the world. Depletion of groundwater sources faster than natural recharge, and pollution of groundwater resources are significant concerns around the world.