ADVERTISEMENTS:
A geological formation that is water bearing or saturated with water and is capable of yielding sufficient quantity of water for economic exploitation is termed as aquifers. Aquifer serves as a transmission conduct from storage reservoirs. It transports water from recharge area to surface bodies of water and other collecting devices. There are many types of aquifers.
They are:
1. Rich Aquifers:
ADVERTISEMENTS:
The value of soil or rock as water bearers depends upon their porosity and size of the particles. However, high porosity does not mean that the aquifer is high water yielding. The best aquifer is that which has massive ground water reservoir at a reasonable depth.
Sand and gravel of fairly uniform size and moderately compacted are the best aquifers followed by well grades and compacted sands and gravels, which too offer good water content.
2. Confined Aquifers:
If the water within the aquifer is confined i.e., held under pressure by an overlaying impervious stratum, the aquifer is known as confined aquifer.
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3. Unconfined Aquifers:
If the aquifer is exposed to atmosphere or possesses a free surface, it is termed as unconfined aquifer.
4. Semi, Unconfined Aquifers:
ADVERTISEMENTS:
If the permeability of the main aquifer is not too great to ignore the horizontal flow components in the covering layer such an aquifer is intermediate between the traditional semi- confined aquifers and the unconfined aquifer and may be termed as a semi-confined aquifer.
5. Aquifuge:
A mask of rock matrix, which neither transmits nor stores water in significant quantity, is called an aquifuge. Such materials can confine water in an artesian aquire.
6. Aquiclude:
If an aquifer is overlaid by a confined bed of impervious material, then this confined bed of overburden is known as aquiclude.
7. Artesian Aquifers and Artesian Wells:
If an aquifer is overlaid by an aquiclude and if the water level in a well penetrated up to this aquifer and rises above the bottom of the overlaying aquiclude, then the aquifer is known as a confined aquifer or an artesian aquifer. The second and even lower water bearing strata will also be known as artesian aquifers.
8. Perched Aquifers:
Perched aquifers are a special case, which is sometimes found to occur within an unconfined aquifer.
ADVERTISEMENTS:
If within the zone of saturation, an impervious deposit below a pervious deposit is found to support a body to saturated materials, and then this body of saturated materials, which is a kind of aquifers, is known as perched aquifer. The top surface of the water held in the perched aquifer is known as perched water table.
