What is an Artesian well? Explain its principle of working with the help of a diagram.
Below the surface of the Earth, there exist concave-shaped layers, some of them are pervious and others are impervious to water. The water layer lying between two impervious layers extends up to the surface of the Earth and the surface water percolates through the previous layers and fills the concave layers with water. Now when a bore is made at the middle of the layer, water comes out through the bore with a great speed because the two ends of the water-filled concave layers are at a higher level than the middle and thus it makes a high pressure at the middle due to the fact that ‘water finds its own level’. As this kind of well was found first in the province of Artois in France and hence it is known as an ‘Artesian well’.