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the groundwater is flowing slowly (Reynolds number less than unity), and the hydraulic conductivity ( K ) is an isotropic scalar . Despite these large assumptions, the groundwater flow equation does a good job of representing the distribution of heads in aquifers due to a transient distribution of sources and sinks.
Pore water pressures below the phreatic level of the groundwater are measured with piezometers. The vertical pore water pressure distribution in aquifers can generally be assumed to be close to hydrostatic. In the unsaturated ("vadose") zone, the pore pressure is determined by capillarity and is also referred to as tension, suction, or
Water content or moisture content is the quantity of water contained in a material, such as soil (called soil moisture), rock, ceramics, crops, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 (completely dry) to the value of the materials' porosity at saturation.
The groundwater may be from precipitation or from more distant groundwater flowing into the aquifer. In areas with sufficient precipitation, water infiltrates through pore spaces in the soil, passing through the unsaturated zone. At increasing depths, water fills in more of the pore spaces in the soils, until a zone of saturation is reached.
Water in the vadose zone has a pressure head less than atmospheric pressure, and is retained by a combination of adhesion (funiculary groundwater), and capillary action (capillary groundwater). If the vadose zone envelops soil, the water contained therein is termed soil moisture. In fine grained soils, capillary action can cause the pores of ...
Groundwater is water that is found underground in cracks and spaces in the soil, sand and rocks. Where water has filled these spaces is the phreatic (also called) saturated zone. 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.
This saturated portion of the capillary fringe is less than the total capillary rise because of the presence of a mix in pore size. If the 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.
According to Groundwater, by Freeze and Cherry (1979), specific storage, [m −1], of a saturated aquifer is defined as the volume of water that a unit volume of the aquifer releases from storage under a unit decline in hydraulic head. [1]