Confined vs Unconfined Aquifer: Difference and Comparison

Confined and Unconfined Aquifers are two phenomena found in nature that many people know about, but very few can exactly define them. These two happen to be a very crucial part of our ecosystem, and therefore it becomes really important to have known the differences between these two.  

Key Takeaways

1. A confined aquifer is a layer of water-bearing rock surrounded by impermeable rock layers, while an unconfined aquifer is open to the surface.
2. Confined aquifers are under pressure and can contain water of higher quality, while unconfined aquifers are more susceptible to contamination.
3. Wells drilled into confined aquifers can be artesian and flow independently, while wells drilled into unconfined aquifers require a pump to extract water.

Confined vs Unconfined Aquifer 

Unconfirmed Aquifers are where the rock is directly open at the surface of the ground, and groundwater is directly recharged, for example, by rainfall or snow melt. And Confined Aquifers are where thick deposits overlay the aquifer and confine it from the Earth’s surface or other rocks.

A Confined Aquifer can be explained as a form of the aquifer that happens to be surrounded by certain rock pieces.

It is built of clay and is surrounded by two or more layers of either rock materials or other related layers of water. It is widely used in irrigation and for human consumption as well.  

But on the contrary, an unconfined aquifer is comparatively exposed and not confined like a confined aquifer.

The sacrifier happens to be on the upper surface, and therefore it happens to be near the land. This is the reason behind this aquifer getting contaminated or polluted very easily due to the pollution and other dirt particles present on the land. 

Comparison Table

Parameters of Comparison	Confined Aquifer	Unconfined Aquifer
Meaning	A form of aquifers that happens to be surrounded by certain rock pieces.	An unconfined aquifer is comparatively exposed and not confined like a confined aquifer.
Another name	Another name for this aquifer is perched aquifer	Another name for this is water table or phreatic aquifer
Close to land	It happens to be relatively distant from the surface of land due to being deep below the land.	it happens to be relatively close to the surface of the land as it is available just below the surface.
Depth	It has more depth.	It has less depth
Water quality	The water present in this aquifer happens to be comparatively clean as there is a very minimum fluctuation in the purity of water.	the water present in this aquifer happens to be comparatively polluted as it is very close to the pollution present on the land
Nature of water	the water in this aquifer happens to be very old and serves long term uses	the water in this aquifer fluctuates a lot and therefore serves short-term uses only

What is Confined Aquifer? 

A Confined Aquifer can be defined as a particular and specific water body that happens to be present deep below the ground level.

It is called a confined aquifer because it happens to be found in confinement with many rock and clay substances. Another name for this aquifer is perched aquifer.

This aquifer is found deep below the ground surface, and therefore it sometimes contains very old water.

Old water here represents the amount of water that has been present in these water bodies for over 1000 years. It happens to be this way because of the minimum fluctuations that occur in this particular aquifer. 

Whenever any well or any other water-providing mechanism is built That infiltrates this particular aquifer, the water in this aquifer rises beyond a particular level.

The pressure found in this uplifted water can be compared with atmospheric pressure, and it can even outrun atmospheric pressure in some cases. 

The hydraulic conductivity of this particular water body happens to be very low compared to other water bodies; however, it still helps in irrigation and normal consumption purposes. 

What is Unconfined Aquifer? 

An unconfined aquifer is comparatively very distinct from any other kind of aquifer as it is found just below the land and contains no hindrance due to rock pieces and clay particles. The aquifer exists just a level above a confined aquifer and the level below the land surface. 

Because of being close to the land surface, the water stored in this particular aquifer happens to be very polluted and contaminated because it receives all the dust and dirt particles directly from the land. 

Also, there are many fluctuations in the water level of this aquifer as it largely depends upon the rainwater, and rainwater does not remain the same throughout the year.

Due to this fluctuating water level, this aquifer provides water for short-term uses ideally and is not suitable for long-term uses as there is no certainty of the amount of water. 

Not just the rain the drought conditions also influence the water level of this aquifer largely, and this is all because of this aquifer being very close to the surface of the earth that it receives almost everything that the earth receives. 

Main Differences Between Confined and Unconfined Aquifer 

1. A confined aquifer happens to be surrounded by many rock and clay pieces, but on the other hand, an Unconfined Aquifer happens to be competitively exposed to the surface of the land. 
2. A Confined Aquifer is found deep beneath the ground level, while an unconfined aquifer is found just below the ground level. 
3. Water in a confined aquifer is clean, while water in an unconfined aquifer is comparatively polluted. 
4. Water in a confined aquifer can serve long-term uses, while water in an unconfined aquifer can serve short-term uses. 
5. A Confined Aquifer is also known as Perched Aquifer, while an unconfined aquifer is also known as Water Table or Phreatic Aquifer. 

References

1. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1998wr900075 
2. https://sfamjournals.onlinelibrary.wiley.com/doi/abs/10.1111/j.1462-2920.2011.02614.x  

Last Updated : 01 August, 2023