The drilling of a water well consists of a hole in the earth that will go through different strata until it reaches an aquifer. Therefore, knowing the existence of these aquifers is essential to locate the point where the deep well will be drilled. The study of hydrogeological reports and the prior knowledge of drilling technicians is essential for this. It is important to always take into account the procedures and goverment permissions.
A fundamental aspect of a water well is depth. In a well drilling we can reach several aquifers (from more superficial to deeper). The deeper aquifers will have more stability in the water supply and less possibility of contamination.
water wells consisting of pipes ranging in size from 6 to 45 cm in diameter and sunk into an aquifer . Tubewells are constructed by installing a pipe below the ground surface passing through different geological formations comprising water-bearing and non-water-bearing strata. Blind pipes (casing pipes) are placed in the non-water-bearing layers and well screens are placed in the water-bearing layers . Several tubewells have been and are being installed worldwide for meeting water demands in domestic,agricultural and industrial sectors. The type of tubewell to be constructed depends on the type of geological formation, intended use of the well and the availability of fund. their construction,development and maintenance Tubewells are also classified based on the depth, method of construction, entry of water into the wells and the type/nature of the aquifer .
As mentioned above, based on the depth of the well, tubewells are classified as shallow tubewells or deep tubewells. Shallow tubewells are of low capacity and their average depth is normally less than 35 m. They mostly tap one aquifer. Deep tubewells are of high capacity and their depth usually ranges from 60 to 300 m . They often tap two or more aquifers. Based on the method of construction, tubewells are classified as bored tubewells, drilled tubewells, driven tubewells and jetted tubewells; they are described in Tubewells in unconsolidated formations generally consist of blind pipes, strainers and gravel pack (if necessary). However, tubewells in hard-rock formations are known as borewells, because the borehole remains stable for most of its depth and the tube is placed only in the upper weathered soil zone No strainer/screen or gravel pack is required for borewells. (for more info visit: pozos de agua )
Moreover, tubewells are also classified as fully penetrating tubewells or partially penetrating tubewells depending on whether the well screen penetrates the saturated thickness of the aquifer fully or partially. In some special hydrogeologic situations, the drilled hole is terminated at the top of the confined aquifer without penetrating it, and hence no strainer is required; such wells are called cavity wells or non-penetrating wells which are described below. In coastal areas, partially penetrating wells with controlled rate of pumping are used expediently to „skim‟ the upper layer of fresh water overlying the saline water. Such tubewells are popularly known as skimming Wells
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