groundwaters

Groundwaters are waters stored beneath the Earth's surface in soil pores and rock fractures. They are a major part of the hydrological cycle, replenished by infiltration and recharge from surface water, and discharged slowly to springs, rivers, or pumped for use. Groundwater moves through permeable layers called aquifers, typically under the influence of gravity and pressure.

Aquifers can be unconfined, where the water table forms the upper surface, or confined, overlain by an impermeable layer that elevates pressure within the aquifer. Groundwater is accessed via wells or emerges as springs, supporting municipal, agricultural, and industrial water supplies in many regions.

Globally, groundwater provides drinking water and irrigation in areas with limited surface water. It supports ecosystems and influences surface water flows through baseflow during dry periods.

Quality varies with geology and pollution sources. Naturally occurring minerals and elements such as arsenic can occur in some regions, while human activities introduce nitrates, pesticides, fuels, or heavy metals. Contamination and over-extraction can cause groundwater depletion, subsidence, reduced streamflow, and saltwater intrusion in coastal aquifers. Protection relies on monitoring, land-use planning, and controlling pollution at recharge zones.

Managed properly, groundwater resources can be sustainably used through measures such as aquifer recharge, groundwater banking, and withdrawal limits. Integrated water-resource management considers surface and groundwater together, with monitoring networks, data sharing, and policies to balance demand with natural recharge.