Importance of Groundwater
The average American consumes 1 to 2 liters of drinking water per day. Virtually all drinking water in the United States comes from fresh surface waters and ground water aquifers.
Groundwater is the water found underground in the cracks and spaces in soil, sand and rock. It is stored in and moves slowly through geologic formations of soil, sand and rocks called aquifers.
A large portion of the world’s fresh water resides underground, stored within cracks and pores in the rock that make up the Earth’s crust. Half of the U.S. population relies on ground water for drinking water. In many parts of the United States, people rely on ground water for drinking, irrigation, industry, and livestock. This is particularly true in areas with limited precipitation, limited surface water resources, or high demand from agriculture and growing populations. Some ecological systems, such as wetlands or surface waters fed by springs and seeps, also rely on ground water.
Public and private wells are installed so that groundwater is made accessible to people. 99% of residents living in rural communities rely on groundwater for their drinking water supply.
An aquifer is an underground geological formation of sand, soil, gravel and rock able to store and yield water. Aquifers can be depleted, which is always a concern. Stressors that can deplete aquifers include changes in precipitation and snowmelt patterns; withdrawal of ground water for drinking, irrigation, and other human uses; and impervious paved surfaces that prevent precipitation from recharging (the replenishment of an aquifer by the absorption of water) ground water. Some deep aquifers may take thousands of years to replenish.
Some consequences of aquifer depletion include:
- Lower lake levels or—in extreme cases—intermittent or totally dry perennial streams. These effects can harm aquatic and riparian plants and animals that depend on regular surface flows.
- Land subsidence and sinkhole formation in areas of heavy withdrawal. These changes can damage buildings, roads, and other structures and can permanently reduce aquifer recharge capacity by compacting the aquifer medium (soil or rock).
- Salt water intrusion. Changes in ground water flow can lead to saline ground water migrating into aquifers previously occupied by fresh ground water.
Importance of Fresh Surface Waters
Surface water such as lakes, ponds, rivers, and streams, hold less than one thousandth of a percent of the water on the planet, but they serve many critical functions for the environment and for human life. These fresh surface waters sustain ecological systems and provide habitat for many plant and animal species. They also support a myriad of human uses, including drinking water, irrigation, wastewater treatment, livestock, industrial uses, hydropower, and recreation. Fresh surface waters also influence the extent and condition of other water resources, including ground water, wetlands, and coastal systems downstream.