Groundwater Systems, Uses, and Challenges

Groundwater Definition and Distribution

Groundwater is water stored beneath Earth's surface in the pore spaces of soil and rock and within fractures in rock formations. It accumulates below the water table, where these spaces become completely saturated. Permeable rock or unconsolidated material that can provide a usable quantity of groundwater is called an aquifer. Groundwater is naturally recharged when precipitation, streams, and rivers infiltrate and percolate downward, and it may return to the surface through springs, seeps, wetlands, or discharge into oceans. It can also be extracted through wells for drinking water, agriculture, industry, and other uses. Groundwater is widely distributed and represents about 30% of the world's readily available freshwater, or roughly 99% of Earth's liquid freshwater. It occurs in many types of geological settings, including sedimentary basins, alluvial river valleys, fractured rocks, karst formations, and large confined aquifer systems such as Australia's Great Artesian Basin. Groundwater storage can be much greater than surface-water storage and may remain underground for days to millions of years. Its distribution, quality, and availability depend on geology, climate, topography, recharge rates, and human extraction.

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Aquifers and Water Tables

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