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Encyclopedia > Groundwater

Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from, and eventually flows to, the surface naturally; natural discharge often occurs at springs and seeps, streams and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... The word ground has several meanings: The surface of the Earth Soil, a mixture of sand and organic material present on the surface of the Earth Ground (electricity), in electrical engineering, something that is connected to the Earth or at the voltage defined as zero (in the US, called ground... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For other uses, see Soil (disambiguation). ... Porosity is a measure of the void spaces in a material, and is measured as a fraction, between 0–1, or as a percentage between 0–100%. The term porosity is used in multiple fields including manufacturing, earth sciences and construction. ... For other uses, see Fracture (disambiguation). ... An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well. ... Cross section showing the water table varying with surface topography as well as a perched water table The water table or phreatic surface is the surface where the water pressure is equal to atmospheric pressure. ... A natural spring on Mackinac Island in Michigan. ... A seep is a wet place, where a liquid, usually water, has oozed from the ground to the surface. ... For the English rock band, see Oasis (band). ... A subtropical wetland in Florida, USA, with an endangered American Crocodile. ... For other uses, see City (disambiguation). ... Village pump redirects here, for information on Wikipedia project-related discussions, see Wikipedia:Village pump. ... Hydrogeology (hydro- meaning water, and -geology meaning the study of the Earth) is the part of hydrology that deals with the distribution and movement of groundwater in the soil and rocks of the Earths crust, (commonly in aquifers). ... Water covers 70% of the Earths surface. ...


Typically, groundwater is thought of as liquid water flowing through shallow aquifers, but technically it can also include soil moisture, permafrost (frozen soil), immobile water in very low permeability bedrock, and deep geothermal or oil formation water. Groundwater is hypothesized to provide lubrication that can possibly influence the movement of faults. It is likely that much of the Earth's subsurface contains some water, which may be mixed with other fluids in some instances. Groundwater may not be confined only to the Earth. The formation of some of the landforms observed on Mars may have been influenced by groundwater. There is also evidence that liquid water may also exist in the subsurface of Jupiter's moon Europa. This article or section does not cite its references or sources. ... While these two men dig in Alaska to study soil, the hard permafrost requires the use of a jackhammer In geology, permafrost or permafrost soil is soil at or below the freezing point of water (0 °C or 32 °F) for two or more years. ... Earth cutaway from core to exosphere. ... Petroleum geology is a term used to refer to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil exploration). ... Lubrication occurs when opposing surfaces are separated by a lubricant film. ... Old fault exposed by roadcut near Harrisburg, Pennsylvania. ... Adjectives: Martian Atmosphere Surface pressure: 0. ... For other uses, see Jupiter (disambiguation). ... Europa is the name of : Europe, the continent, in most European languages (most Germanic languages, Latin and some Romance languages, and some Slavic Languages) Europa (mythology), a beautiful Phoenician princess in Greek mythology Europa (moon), the smallest of the Galilean moons of planet Jupiter Europa, a small island in the...


Aquifers

Main article: Aquifer

An aquifer is a layer of relatively porous substrate that contains and transmits groundwater. When water can flow directly between the surface and the saturated zone of an aquifer, the aquifer is unconfined. Because water tends to flow downward due to gravity, the deeper parts of unconfined aquifers are usually more saturated with groundwater. An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well. ... An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well. ...


The upper level of this saturated layer of an unconfined aquifer is called the water table or phreatic surface. Below the water table, where generally all pore spaces are saturated with water is the phreatic zone. Cross section showing the water table varying with surface topography as well as a perched water table The water table or phreatic surface is the surface where the water pressure is equal to atmospheric pressure. ... Cross section showing the water table varying with surface topography as well as a perched water table The water table or phreatic surface is the surface where the water pressure is equal to atmospheric pressure. ... This article does not cite any references or sources. ...


Substrate with relatively low porosity that permits limited transmission of groundwater is known as an aquitard. An aquiclude is a substrate with porosity that is so low it is virtually impermeable to groundwater.


A confined aquifer is an aquifer that is overlain by a relatively impermeable layer of rock or substrate such as an aquiclude or aquitard. If a confined aquifer follows a downward grade from its recharge zone, groundwater can become pressurized as it flows. This can create artesian wells that flow freely without the need of a pump or rise to a higher elevation than the static water table at the above, unconfined aquifer. Geological strata giving rise to an Artesian well An artesian aquifer is an aquifer whose water is overpressurized. ... Cross section showing the water table varying with surface topography as well as a perched water table The water table or phreatic surface is the surface where the water pressure is equal to atmospheric pressure. ...


The characteristics of aquifers vary with the geology and structure of the substrate and topography in which they occur. Generally, the more productive and useful aquifers occur in sedimentary geologic formations. By comparison, weathered and fractured crystalline rocks yield relatively smaller quantities of groundwater in many environments. Unconsolidated to poorly cemented alluvial materials that have accumulated as valley-filling sediments in major river valleys and geologically subsiding structural basins are included among the most productive sources of groundwater.


The high specific heat capacity of water and the insulating effect of soil and rock can mitigate the effects of climate and maintain groundwater at a relatively steady temperature. In some places where groundwater temperatures are maintained by this effect at about 50°F/10°C, groundwater can be used for controlling the temperature inside structures at the surface. For example, during hot weather relatively cool groundwater can be pumped through radiators in a home and then returned to the ground in another well. During cold seasons, because it is relatively warm, the water can be used in the same way as a source of heat for heat pumps that is much more efficient than using air. The relatively constant temperature of groundwater can also be used for heat pumps. Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval. ... A heat pump is a machine or device that moves heat from one location (the source) to another location (the sink), using work. ... A heat pump is a machine or device that moves heat from one location (the source) to another location (the sink), using work. ...


External links

The Woods Hole Oceanographic Institution (WHOI) is a private, nonprofit research and higher education facility dedicated to the study of all aspects of marine science and engineering and to the education of marine researchers. ...

  Results from FactBites:
 
The Groundwater Foundation (105 words)
The Groundwater Foundation is a nonprofit organization dedicated to educating and motivating people to care for and about groundwater.
New Groundwater Foundation President Jane Griffin Brings Vision of Growth
Discussing the groundwater topics that are on your mind.
Groundwater (1823 words)
Groundwater is water that exists in the pore spaces and fractures in rock and sediment beneath the Earth's surface.
Groundwater is in constant motion, although the rate at which it moves is generally slower than it would move in a stream because it must pass through the intricate passageways between free space in the rock.
Groundwater is an active weathering agent and can leach ions from rock, and, in the case of carbonate rocks like limestone, can completely dissolve the rock.
  More results at FactBites »

 
 

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