WATER WELL

A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access water in underground aquifers. The well water is drawn by an electric submersible pump or a mechanical pump (eg from a water-pumping windmill It can also be drawn up using containers, such as buckets, that are raised mechanically or by hand. Although not essential, a storage tank with a pressure of 40–60 psi is usually added to the system (after the pump), so the pump does not need to operate constantly. To reduce the electricity required to pump up the water, often, a cistern is also added along with a small second pump (see schematic below).

Wells can vary greatly in depth, water volume and water quality. Well water typically contains more minerals in solution than surface water and may require treatment to soften the water by removing minerals such as arsenic, iron and manganese. Until recent centuries, all artificial wells were pumpless dug wells of varying degrees of formality. Their indispensability has produced numerous literary references, literal and figurative, to them, including the Christian Bible story of Jesus meeting a woman at Jacob's well (John 4:6) and the "Ding Dong Bell" nursery rhyme about a cat in a well.

Such primitive dug wells were excavations with diameters large enough to accommodate men with shovels digging down to below the water table. Relatively formal versions tended to be lined with laid stones or brick; extending this lining into a wall around the well presumably served to reduce both contamination and injuries by falling into the well. The iconic American farm well features a peaked roof above the wall, reducing airborne contamination, and a cranked windlass, mounted between the two roof-supporting members, for raising and lowering a bucket to obtain water.

Drilled wells can get water from a much deeper level by mechanical drilling.Drilled wells with electric pumps are currently used throughout the world, typically in rural or sparsely populated areas, though many urban areas are supplied partly by municipal wells.Drilled wells are typically created using either top-head rotary style, table rotary, or cable tool drilling machines, all of which use drilling stems that are turned to create a cutting action in the formation, hence the term 'drilling'. Most shallow well drilling machines are mounted on large trucks, trailers, or tracked vehicle carriages. Water wells typically range from 20 to 600 feet (180 m), but in some areas can go deeper than 3,000 feet (910 m).Rotary drilling machines use a segmented steel drilling string, typically made up of 20-foot (6.1 m) sections of steel tubing that is threaded together, with a bit or other drilling device at the bottom end. Some rotary drilling machines are designed to install (by driving or drilling) a steel casing into the well in conjunction with the drilling of the actual bore hole.