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Groundwater is fresh water located in the subsurface pore space of soil and rocks.It is also water that is flowing within aquifers below the water table.Sometimes it is useful to make a distinction between groundwater that is closely associated with surface water, and deep groundwater in an aquifer (called "fossil water" if it infiltrated into the ground millennia ago [8]).
This term is generally used to refer to a small local area of ground water that occurs at an elevation higher than a regionally extensive aquifer. The difference between perched and unconfined aquifers is their size (perched is smaller). Confined aquifers are aquifers that are overlain by a confining layer, often made up of clay.
In the aquifer, groundwater flows from points of higher pressure to points of lower pressure, and the direction of groundwater flow typically has both a horizontal and a vertical component. The slope of the water table is known as the “hydraulic gradient”, which depends on the rate at which water is added to and removed from the aquifer and ...
Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer .
The specific storage is the amount of water that a portion of an aquifer releases from storage, per unit mass or volume of the aquifer, per unit change in hydraulic head, while remaining fully saturated. Mass specific storage is the mass of water that an aquifer releases from storage, per mass of aquifer, per unit decline in hydraulic head:
Hard rock aquifers are composed of igneous rock or metamorphic rock or both. Low porosity hard rock with different orientation of joints and fractures provides space for the flow of groundwater, forming a hard rock aquifer. Groundwater flow direction is controlled by the orientation of fractures and geological structures like dykes. [11] [12]
Groundwater is stored in two zones, one being the saturated zone, or Aquifer, the other is the pore space of unsaturated soil immediately below the ground surface. Soil moisture is the water held between soil particles in the root zone (rhizosphere) of plants, generally in the top 200 cm of soil. Water storage in the soil profile is extremely ...
Groundwater is stored in and moves slowly (compared to surface runoff in temperate conditions and watercourses) through layers or zones of soil, sand and rocks: aquifers. The rate of groundwater flow depends on the permeability (the size of the spaces in the soil or rocks and how well the spaces are connected) and the hydraulic head (water ...