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A perched water table (or perched aquifer) is an aquifer that occurs above the regional water table. This occurs when there is an impermeable layer of rock or sediment ( aquiclude ) or relatively impermeable layer ( aquitard ) above the main water table/aquifer but below the land surface.
Cross section showing the water table varying with surface topography as well as a perched water table The vadose zone , also termed the unsaturated zone , is the part of Earth between the land surface and the top of the phreatic zone , the position at which the groundwater (the water in the soil's pores) is at atmospheric pressure ("vadose" is ...
In geotechnical engineering, watertable control is the practice of controlling the height of the water table by drainage.Its main applications are in agricultural land (to improve the crop yield using agricultural drainage systems) and in cities to manage the extensive underground infrastructure that includes the foundations of large buildings, underground transit systems, and extensive ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 24 December 2024. Water located beneath the ground surface An illustration showing groundwater in aquifers (in blue) (1, 5 and 6) below the water table (4), and three different wells (7, 8 and 9) dug to reach it. Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in ...
This groundwater is a major source of fresh water for many regions, however can present a number of challenges such as overdrafting (extracting groundwater beyond the equilibrium yield of the aquifer), groundwater-related subsidence of land, and the salinization or pollution of the groundwater.
Use of groundwater, especially for irrigation, may also lower the water tables. Groundwater recharge is an important process for sustainable groundwater management, since the volume-rate abstracted from an aquifer in the long term should be less than or equal to the volume-rate that is recharged.
The part above the water table is the vadose zone (also called unsaturated zone). The phreatic zone size, color, and depth may fluctuate with changes of season, and during wet and dry periods. [ 1 ] [ 2 ] Depending on the characteristics of soil particles, their packing and porosity, the boundary of a saturated zone can be stable or instable ...
Cross-section of a hillslope depicting the vadose zone, capillary fringe, water table, and saturated zone. The capillary fringe is the subsurface layer in which groundwater seeps 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.