Detailed presentation on types of aquifers

1. AQUIFERs and it’s types:
Definition : “An aquifer is a saturated geologic formation that
will yield a usable quantity of water to a well or a spring”.
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2. some of the important points about aquifers:
• Aquifers are a vital source of water for drinking, irrigation
and industrial uses.
• The water in an aquifer is held in the spaces between the grains
of rock or sediment.
• The amount of water that an aquifer can hold depends on its porosity
and permeability.
• There are two main types of aquifers: confined and unconfined.
• Aquifers are recharged by precipitation and surface water.
• Over-pumping of aquifers can lead to a number of problems,
including water shortages, saltwater intrusion, and land subsidence.
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3. Saturated and unsaturated zone:
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Subsurface water occurs in two different zones,
1. Unsaturated zone:
• Zone, located immediately beneath the land
surface in most areas, contains both water and
air in the voids. This zone is referred to as the
unsaturated zone.
• Capillary Fringe
2. Saturated zone:
• The unsaturated zone is almost always
underlain by a second zone in which all voids
are full of water. This zone is defined as the
saturated zone.
• Water in the saturated zone is referred to as
ground water and is the only subsurface water
available to supply wells and springs.

4. Aquifers and confined beds:
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• All geologic material beneath the
earth's surface is either a potential
aquifer or a confining bed.
• A confining bed is a geologic unit
which is relatively impermeable and
does not yield usable quantities of
water.
• referred to as aquitards

5. Types of Aquifers:
Aquifers are mainly divided into 3 types:
1. Unconfined Aquifer:
A groundwater aquifer is said to be unconfined when its upper
surface (water table) is open to the atmosphere through permeable
material.
2. Confined Aquifer:
A confined aquifer is a water-bearing stratum that is confined or
overlain by a rock layer that does not transmit water in any
appreciable amount or that is impermeable.
3. Perched Aquifer:
A perched water table (or perched aquifer) is an aquifer that occurs above the
regional water table. This occurs when there is an impermeable layer of rock
or sediment (aquiclude) or relatively impermeable layer (aquitard) above the
main water table/aquifer but below the land surface. 5

6. Unconfined Aquifer:
Some of the key features of unconfined aquifers:
 The water table is at atmospheric pressure.
 The water level in the aquifer will rise and fall in response to changes in recharge and discharge.
 Unconfined aquifers are typically recharged by rainwater or snowmelt.
 They are commonly used as sources of drinking water.
 They are more vulnerable to contamination than confined aquifers.
Some examples of unconfined aquifers include:
 Coastal sands
 Alluvial deposits in river valleys
 Sand and gravel aquifers
 Fractured bedrock aquifers
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7. Confined Aquifer:
Some of the key features of confined aquifers:
• They are sandwiched between two layers of impermeable rock.
• The water in the aquifer is under pressure.
• The water in the well will rise above the level of the aquifer.
• They are a valuable source of groundwater.
• They are relatively less susceptible to contamination than unconfined aquifers.
• They are commonly used as sources of Commercial or Industrial water.
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8. Picture Showing the features Corresponding to Aquifers
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