Groundwater is the water located beneath the Earth's surface in the cracks and spaces of soil, sand, and rock formations. It is stored in permeable geological formations called aquifers, which can be made of materials like gravel, sand, sandstone, or fractured rock such as limestone. The water moves slowly through these formations, filling the pores and fractures in the subsurface
. The upper boundary of the saturated zone where groundwater is found is called the water table. Groundwater is replenished or recharged primarily by rain and snowmelt that infiltrate down through the soil and rock layers. It can naturally discharge to the surface through springs or seep into lakes and streams, helping to maintain surface water levels
. Groundwater is a critical resource, providing drinking water to over half of the population in the United States and supporting agricultural irrigation and industrial uses worldwide. It is generally cleaner than surface water due to natural filtration as it moves through soil and rock
. However, groundwater can be vulnerable to pollution from human activities such as landfills, septic tanks, leaking underground storage tanks, and excessive use of fertilizers and pesticides. Over-extraction can also lower the water table, causing wells to dry up and leading to water shortages in some regions
. In summary, groundwater is the subsurface water stored in soil and rock pores and fractures, essential for drinking water, agriculture, and ecosystems, but it requires careful management to prevent depletion and contamination.
