Artesian well

A type of well where water is under pressure and flows to the surface naturally

An artesian well is a type of well in which water is under pressure and flows to the surface naturally without the need for pumping. This occurs when the well taps into a confined aquifer containing groundwater under positive pressure.

Formation of Artesian Wells

Diagram of an artesian aquifer

Artesian wells are formed when a well is drilled into a confined aquifer. A confined aquifer is a water-bearing stratum that is trapped between two impermeable layers of rock or clay. The water in the aquifer is under pressure because it is trapped between these layers. When a well penetrates the aquifer, the pressure is released, allowing the water to rise to the surface.

The pressure in the aquifer is typically due to the elevation of the recharge area, where water enters the aquifer. This area is usually at a higher elevation than the point where the well is drilled, creating a natural pressure gradient.

Characteristics

Illustration of an artesian well

Artesian wells are characterized by their ability to bring water to the surface without mechanical pumping. The water in an artesian well is often cleaner and more protected from surface contamination than water from unconfined aquifers, as it is shielded by the impermeable layers above and below the aquifer.

The flow rate of an artesian well can vary depending on the pressure in the aquifer and the size of the well. In some cases, the pressure is sufficient to create a flowing artesian well, where water continuously flows out of the well. In other cases, the pressure may only be enough to bring the water to the surface, requiring additional pumping to extract it.

Historical and Modern Uses

Seabees tapping a new artesian well

Historically, artesian wells have been used as a reliable source of water for agriculture, industry, and domestic use. The natural pressure of the water made them an attractive option before the advent of modern pumping technology.

In modern times, artesian wells are still used in many parts of the world, particularly in rural and remote areas where access to electricity for pumping is limited. They are also valued for their potential to provide clean, uncontaminated water.

Environmental Considerations

While artesian wells can provide a sustainable source of water, over-extraction can lead to a decrease in pressure within the aquifer, reducing the flow of water and potentially leading to the depletion of the aquifer. It is important to manage the extraction of water from artesian wells to ensure the long-term sustainability of the water supply.

Examples

Artesian well in Virttaa

Artesian wells can be found in various parts of the world, including the Great Artesian Basin in Australia, which is one of the largest and most well-known artesian basins. Other examples include the Paris Basin in France and the London Basin in the United Kingdom.

Related Pages

• Aquifer
• Groundwater
• Well
• Hydrogeology