(a) What is a spring?
A spring is a natural outflow of water from underground to the surface of the earth. The water may seep out gently or gush out strongly. The outflow of water occurs at or below the plane where the water table intersects the surface.
(b) Formation of springs;
In areas of tilted strata, where permeable and impermeable rock alternate, water emerges at the base of the permeable layer. In well jointed rocks, water may percolate downwards until it reaches a joint which emerges at the surface. The water may come to the surface through the joint to form a spring. Where a dyke or sill of impermeable rock is intruded through permeable rocks it causes the water table to reach the surface. The water issues out as spring. In limestone or chalk escarpments, where the permeable rock lies between impermeable strata, water issues at the foot of the scarp as springs. In Karst regions rivers often disappear underground and may re-emerge as a resurgence.