WHAT IS Groundwater

Groundwater is water that is found underground rather than on the surface. Groundwater is created when rain seeps into the ground through permeable surfaces rather than evaporating into the atmosphere. It can be accessed through wells drilled or dug into the ground.


Groundwater is considered all the water underground. There are three primary layers under the land surface: the unsaturated zone, the water table, and the saturated zone. The unsaturated zone is right beneath the land surface and is the barrier between the land surface and the water table. The water table is the next layer. It may be a few feet or a few hundred feet deep, and it rises or falls depending on how much water is in it. It gets recharged by water flowing into it through to surface from rain or snow. The saturated zone in underneath the water table and is filled with sand, gravel and other rocks and large objects that make up the aquifer. Groundwater from the aquifer discharges into lakes and streams, or it can be accessed by drilling wells through the unsaturated zone and water table into the aquifer.

Groundwater is used as the primary water source for half the population of the United States, especially those living in rural areas. Groundwater is used to provide water to people. It is also used by farmers to water crops and ranchers to provide water to livestock. 

Chemicals and pollutants that are dissolved in water at the surface can filter into groundwater reservoirs, such as aquifers. This poses a substantial environmental threat because the chemicals can affect the health of those drawing on groundwater sources. Polluted groundwater can have a substantial economic impact if livestock become sick or farmland polluted. Stationary sources of pollution include landfills and lined ponds for wastewater, while spills of hazardous chemicals can also pose threats.

Groundwater Controversies

The development and increased use of hydraulic fracturing, or fracking, to gain access to underground sources of oil and natural gas has brought renewed focus to groundwater threats. Fracking uses pressurized chemicals and water to break into underground reservoirs. Much of the water used in this process remains underground as the reservoir is depleted, but a portion is brought up to the surface. This water must be treated in order to be safe, but groundwater supplies can become unsafe and unusable if untreated water seeps back underground.

In some areas unrestricted use of groundwater by farmers has led to a depletion of groundwater resources, which causes significant problems during drought conditions. Some states, such as California, have historically considered groundwater a private natural resource rather than one owned by the public, allowing farmers and landowners to extract as much water as they wanted.

Large corporations have also drawn groundwater to sell as bottled water by striking deals with state environmental agencies to draw water from public reservoirs. These contracts, which are written so the corporations do not have to pay the states for the water they take, may not be legal.