Aquifers Aquifers 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. A common misconception is that groundwater exists in underground rivers (e.g. caves where water flows freely underground). This is only true in eroded limestone areas known as Karst topography which make up only a small percentage of Earth's area. More usual is that the pore spaces of rocks in the subsurface are simply saturated with water — like a kitchen sponge, which can be pumped out and used for agricultural, industrial or municipal uses. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. ...more on Wikipedia about "Aquifer"
An aquitard is a geological formation of layers comprised either of clay, with tiny connected pores, or on non-porous rock that restrict water flow from one aquifer to another. ...more on Wikipedia about "Aquitard"
An artesian aquifer is a confined aquifer whose water is pressurized. Water will thus flow out of an artesian well without pumping. ...more on Wikipedia about "Artesian aquifer"
The Bas Saharan Basin is an artesian basin aquifer system which covers most of the Algerian and Tunisian Sahara and extends to ...more on Wikipedia about "Bas Saharan Basin"
The capillary fringe is the subsurface layer in which water molecules seep up from a water table by capillary action to fill pores. Pores at the base of the capillary fringe are filled with water due to tension saturation. This saturated portion of the capillary fringe is less than total capillary rise because of the presence of a mix in pore size. If pore size is small and relatively uniform, it is possible that soils can be completely saturated with water for several feet above the water table. Alternately, the saturated portion will extend only a few inches above the water table when pore size is large or non-uniform. Capillary action supports an unsaturated zone above the saturated base within which water content decreases with distance above the water table. In soils with a wide range in pore size, the unsaturated zone can be several times thicker than the saturated zone. ...more on Wikipedia about "Capillary fringe"
The Edwards Aquifer one of the most prolific artesian aquifers in the world. Located on the western edge of Texas' Edwards Plateau, it cycles about 500,000 gallons (1,900,000 liters) of water a year and directly serves about two million people. The Edwards Aquifer is also home to several unique and endangered species. ...more on Wikipedia about "Edwards Aquifer"
The Floridan Aquifer is a highly productive artesian Carbonate-rock aquifer system located beneath the coastal regions of the Southeastern United States. ...more on Wikipedia about "Floridan Aquifer"
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The Great Artesian Basin provides the only reliable source of water through much of inland Australia and is the largest artesian basin in the world. It underlies 23% of the continent, including most of Queensland, the south-east corner of the Northern Territory, the north-east part of South Australia, and northern New South Wales. The basin is 3000 metres (10,000 ft) deep in places and has been estimated to contain between 9 and 65 billion megalitres (7 to 52 billion acre-feet) of groundwater. ...more on Wikipedia about "Great Artesian Basin"
Groundwater is water which may be flowing within aquifers below the water table. Within aquifers, the water flows through the pore spaces in unconsolidated sediments and the fractures of rocks. Groundwater is recharged from, and eventually flows to, the surface naturally; natural discharge often occurs at springs and seeps and can form oases or swamps. Groundwater is also often withdrawn for agricultural, municipal and industrial use through man-made wells. The study of the distribution and movement of groundwater is hydrogeology. ...more on Wikipedia about "Groundwater"
The Laurentian River System is an ancient river in southern Ontario, Canada. The river predates the recent ice ages. The river valley was filled with glacial debris. Water still flows down this old valley -- underground. The source of the aquifer is thought to be near Georgian Bay, approximately 200 km away. ...more on Wikipedia about "Laurentian River System (Ontario)"
The following is a partial list of aquifers around the world. A category-based list of aquifers is also available. ...more on Wikipedia about "List of aquifers"
The Ogallala Aquifer, also known as the High Plains Aquifer, is a shallow water table aquifer located beneath the Great Plains in the United States. One of the world's largest aquifers, it lies under about 174,000 mi² (450,000 km²) in portions of the eight states of South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas. It was named in 1899 by N.H. Darton from its type locality near the town of Ogallala, Nebraska. ...more on Wikipedia about "Ogallala Aquifer"
In geology, permeability is a measure of the ability of a material (typically, a rock or unconsolidated alluvial material) to transmit fluids through it. It is of great importance in determining the flow characteristics of hydrocarbons in oil and gas reservoirs, and of groundwater in aquifers. The usual unit for permeability is the darcy, or more commonly the milli-darcy or md (1 darcy 10−12m²). ...more on Wikipedia about "Permeability (geology)"
Used in geology, building science and hydrogeology, the porosity of a porous medium (such as rock or sediment) is the proportion of the non-solid volume to the total volume of material, and is defined by the ratio: ...more on Wikipedia about "Porosity"
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