Many people the world over rely on well water to access fresh water for drinking. In the US alone, more than 17 million homes depend on a well to meet their drinking water needs. Water wells are pits, holes, or pipes that are dug, drilled, or driven into the ground to a depth below the water table in order to access groundwater that is contained in aquifers underground.
In more primitive cultures, and in countries that lack the latest technology and modern equipment, a water well is still dug by hand using a pick and shovel to dig to below the water table. This can be achieved fairly easily if the substrate is soft, and the pool is not too deep underground. These wells are lined with brick, stone, or precast concrete rings. Because hand dug wells exploit shallow water reservoirs, they are prone to contamination from surface pollutants such as sewage, pesticides, etc., and may also suffer from reduced flow rates should the water table drop. However, it is fairly simple to deepen them should the water table drop significantly.
If the soil is soft,a water well can also be constructed by driving a pipe into the ground using a driver. The pipe is fitted with a screen to prevent sand and grit from being sucked into the pipe when pumping commences. Wells constructed using this method are also limited to shallow water tables, and face similar problems as hand dug wells above.
In developed countries, where modern technology and equipment is readily available, a water well are typically constructed by drilling using a drill rig fitted with a rotary, percussion, or auger drill bit, depending on the type of substrate that needs to be penetrated. The advantage that this method offers is that water wells can be drilled much deeper to access groundwater held in aquifers deep underground. While water wells that are hand dug or driven are restricted to shallow depths, and do not penetrate an impermeable layer of substrate, drilled water wells can be classified as either shallow confined, or deep unconfined water wells if they are drilled through an impermeable layer of substrate to access groundwater stored in a confined aquifer – where the well water is confined between two layers of impermeable rock or clay. Drilled water wells are lined with casing and fitted with a surface seal to prevent contamination of the well water from surface pollutants.
Where the well water does not flow freely to the surface under pressure, it will need some method of being delivered to the surface. While more primitive shallow hand dug well sometimes relies on a simple bucket and winch system to bring the well water to the surface, the more favored modern approach is to pump it out.
While deeper well water tends to be less prone to contamination than shallow wells, some precautions need to be taken to prevent contamination by bacteria, viruses, and chemical pollutants in all wells that supply drinking water.
Precautionary measures may include prevention, water testing, and treatment using chemicals or filtration to remove any pollutants that may pose a health risk in drinking water supplied by well water.