Ground Water and Aquifer

Ground water is water located beneath the ground surface in soil pore spaces and in the features of lithologic formations. A unit of rock or on unconsolidated deposit is called an aquifer when it can yield a useble quantity of water. The depth at which soil pore spaces of fractures and voids in rock become completely saturated with water is called the water table. Ground water is recharge from and eventually flows to, the surface naturally; natural discharge often occurs at springs and the study of distribution and movement of ground water is hydrology, also called ground water hydrology. Typically, ground water is thought of as liquid water flowing though shallow aquifers, but technically it can also included soil moisture, permafrost (frozen soil), immobile water in very low permeability bedrock, and deep geothermal or oil formation water. Ground water is hypothesized to provide lubrication that can possibly influence the movement of fault. It is likely that much of the Earth’s subsurface contains some water, which may be mixed with other fluids in some instances. Ground water may not be confined only to the Earth. The formation of some water. There is also evidence that liquid water may also exist in the subsurface of Jupiter’s Europe.

1. Aquifer.

An aquifer is a layer of relatively porous substrate that contains and transmits ground water. When water can flow directly between the surface and the saturated zone of an aquifer, the aquifer is unconfined. The deeper parts of unconfined aquifers are usually more saturated with ground water since gravity causes water to flow downward. The upper level of this saturated layer of an unconfined aquifer is called the water table or preathic surface. Below the water table, where generally all pore spaces are saturated with water is the phreatic zone. Substrate with relatively low porosity that permits limited transmission of ground water is known as an aquitard. An aquiclud is a substrate with porosity that is so low it is virtually impermeable to ground water. A confined aquifer follows a downward grade from its recharge zone, ground water can become pressurized as it flows. This can create Artesian well. Artesian wells that flow freely without the need of a pump or rise to higher elevation than the static water table at the above, unconfined aquifer. The characteristic of aquifers vary with the geology and structure of the substrate and topography in which they occur. Generally, the more productive and useful aquifer occur in sedimentary geologic formations. By comparison, weathered and fractured crystalline rocks yield relatively smaller quantities of ground water in many environments. Unconsolidated to poorly cemented alluvial materials that have accumulated as valley-filling sediment in major river valleys and geologically subsiding structural basins are included among the most productive sources of ground water. The high specific heat capacity of water and the insulating effect of soil and rock can mitigate the effect of climate and maintain ground water at a relatively steady temperature. In some place where ground water temperatures are maintained by this effect at about 50ºF / 10ºC, groundwater can be used for controlling the temperature inside structures at the surface. For example, during hot weather relatively cool groundwater can be pumped thorough radiators in a home and then returned to the ground in another well. During cold season, 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  ground water can also be used for heat pumps.