Aquifers are mainly of two types.

  1. Unconfined aquifer.
  2. Confined aquifer.

1. Unconfined Aquifer.

  • The topmost water bearing strata having no confining impermeable over-burden is known as unconfined aquifer.
  • This aquifer is also know non-artesian aquifer or water table aquifer.
  • Water table in such an aquifer varies in undulating form depending upon the storage of water within it.
  • The gravity wells are construct to tap water from unconfined aquifer only.
  • The water rise in such wells is equal to water rise in a piezometer connected to the water table.

Confined and unconfined aquifers.


2. Confined Aquifer.

  • It is such an aquifer which remains overladen by an impermeable strata or aquiclude.
  • The water is under pressure in this aquifer.
  • Confine aquifers are also know as artesian aquifers.
  • They can be consider analogous to pipe lines flowing under pressure.
  • The static pressure at a point in a confin aquifer is equal to the elevation of
  • the water table recharging the area minus the loss of head through the aquifer to the point under consideration.
  • The rise of water in the well, taping confin aquifer is determine by connecting a piezometer tube to this layer and noting the rise of water in the tube.
  • Artesian wells are those which are construct sufficiently deep to tap water from 2nd or even lower water bearing strata.
  • These wells are generally small in size with diameters less than 30 cm.
  • When pressure of water in a certain water bearing formation is so high that water rises above the ground level automatically such a well is known as flowing well.
  • If, however, the water level in such a well remain below the ground level, but is above the local water table it is know as the artesian well.