15 Difference and Similarities between Confined and Unconfined Aquifer

15 Difference and Similarities between Confined and Unconfined Aquifer

Differences and Similarities between Confined and Unconfined Aquifer

Compiled by Stanley Udegbunam || Dec 04, 2020

In today’s article, we will be looking at not only the difference between confined and unconfined aquifer but also its similarities.

You can click on any listing in the table of content below to just straight at your area of interest.

Without further ado, let’s get started.

AFRILCATE

OVERVIEW OF AQUIFER

Aquifers are found in the area saturated with water.

They are the underground layers of rock that hold the groundwater.

Groundwater enters an aquifer as precipitates fall on the earth’s surface and seep through the soil.

The amount of time that groundwater remains in aquifers is called its residence time and it can vary widely from a few days or week to thousands of years.

There are two types of aquifers; Unconfined and Confined aquifer.

Using a tabular representation, let’s look at the difference between the aquifer type.

DIFFERENCE BETWEEN CONFINED AND UNCONFINED AQUIFER

Differences
CONFINED AQUIFER

UNCONFINED AQUIFER
DEFINITIONIt’s an aquifer with a layer of permeable material above itThis aquifer is overlain by layers of impermeable rock or clay.
AQUIFER FORMATIONForms when water infiltrates the soil and percolates downward to the water bed over layers of porous and permeable materials.
Forms when water seeps between layers of impermeable rocks under the gradual influence of pressure and gravity.
SURFACE PROXIMITY
It occurs near the earth surface.It generally occurs at significant depth below the earth’s surface.
CONTAMINATION
At a greater risk of contamination from external sources like rivers and from poorly managed human activities like septic leaks and excessive spray of pesticides and herbicides on farmlands.
The confining layer offer some protection from surface contamination.
RECHARGE RATE
Though aquifers take a long time to get recharged, the recharge rate is faster in unconfined aquifer.Takes a longer time to get recharged.
ALTERNATIVE NAMES
Also known as water-table aquifer.
Popularly called Artesian aquifer.
SURROUNDING LAYERS
Usually guarded by an aquitard above it and an aquiclude below it.
Confined by an aquiclude above and below it. In rare cases, aquifuge is found below it.
FLOW RATEHave a higher flow rate even when its retarded by an aquitard.
Have a lower flow rate due to the presence of impermeable linings.
HYDRAULIC CONDUCTIVITY
Higher hydraulic conductivityLower hydraulic conductivity
STORATIVITY LEVELHave storativities greater than 0.01
Have storativities values much less than 0.01.
Differences
CONFINED AQUIFER

UNCONFINED AQUIFER
DEFINITIONIt’s an aquifer with a layer of permeable material above itThis aquifer is overlain by layers of impermeable rock or clay.
AQUIFER FORMATIONForms when water infiltrates the soil and percolates downward to the water bed over layers of porous and permeable materials.
Forms when water seeps between layers of impermeable rocks under the gradual influence of pressure and gravity.
SURFACE PROXIMITY
It occurs near the earth surface.It generally occurs at significant depth below the earth’s surface.
CONTAMINATION
At a greater risk of contamination from external sources like rivers and from poorly managed human activities like septic leaks and excessive spray of pesticides and herbicides on farmlands.
The confining layer offer some protection from surface contamination.
RECHARGE RATE
Though aquifers take a long time to get recharged, the recharge rate is faster in unconfined aquifer.Takes a longer time to get recharged.
ALTERNATIVE NAMES
Also known as water-table aquifer.
Popularly called Artesian aquifer.
SURROUNDING LAYERS
Usually guarded by an aquitard above it and an aquiclude below it.
Confined by an aquiclude above and below it. In rare cases, aquifuge is found below it.
FLOW RATEHave a higher flow rate even when its retarded by an aquitard.
Have a lower flow rate due to the presence of impermeable linings.
HYDRAULIC CONDUCTIVITY
Higher hydraulic conductivityLower hydraulic conductivity
STORATIVITY LEVELHave storativities greater than 0.01
Have storativities values much less than 0.01.
aquifer and water cycle

confined and unconfined aquifer

SIMILARITIES BETWEEN CONFINED AND UNCONFINED AQUIFER

The similarities between confined and unconfined aquifers are:

  1. They both have an underlying impermeable lining.
  2. Water flows through them by percolation
  3. They are found underground where they serve as a storage house for
  4. In cases when their water content is very low, they can both be replenished by artificial recharge
  5. The study of underground water flow in both unconfined and confined aquifer is known as hydrogeology

KEY TERMS 

There are some basic key terms to know when talking about aquifers. They include:

  • Recharge
  • Artificial Recharge
  • Storativity
  • Hydraulic Conductivity
  • Percolation
  • Hydrogeology
RECHARGE

Recharge is the process where surface water or precipitations infiltrates the soil and percolates downwards to the water table.

Groundwater Recharge is the primary method through which water enters the aquifer.

Learn more: Groundwater Recharge

ARTIFICIAL RECHARGE

Artificial recharge is the process of increasing the amount of water that enters an aquifer through planned, human-controlled means.

Groundwater is recharged either naturally or through artificial means.

The artificial means of recharging groundwater is employed when the rate of underground water consumption exceeds it’s natural rate of recharge.

There are various means of achieving artificial groundwater recharge and they are all documented in our explanatory guide.

Learn more: Artificial Recharge Guide

STORATIVITY

This is the volume of water removed from a unit area of an aquifer for a unit drop in hydraulic head.

HYDRAULIC CONDUCTIVITY

This is the ease with which fluid moves through pore space and fractures.

It is different from permeability which relates specifically to the properties of the porous material only. Permeability doesn’t consider the property or the fluid type.

In contrast, hydraulic conductivity considers both the porous medium and the flowing fluid so it affected by the density and viscosity of the flowing fluid.

PERCOLATION

Percolation is the downward movement of water through soil layers due to gravity and capillary forces.

Percolation is an important process required to replenish aquifers that hold groundwater in the saturation zone.

The speed at which that water moves through different soil layers is known as percolation rate.

Structures known as percolation tanks are also designed for the purpose of groundwater recharge.

Learn more: All about Percolation

HYDROGEOLOGY

Hydrogeology is the study of the distribution, flow, and quality of underground water.

It is an aspect of geology and it’s also called groundwater-hydrology or geohydrology.

Hydrogeology maps and quantifies the water stored in underground aquifers and occasionally surface systems.

A practitioner of hydrogeology is called a hydrogeologist.

Learn more: Hydrogeology Study

Still curious?

Based on readers’ requests, we recently published an in-depth article on aquifer to give you an extended knowledge of the topic.

See it here:  Aquifer – Meaning, Types and Importance

DO YOU KNOW?

Unlike surface water, groundwater can move as slow as a meter per year.

This means it can take several thousands of years for underground aquifers to become replenished.

DO YOU KNOW?

Unlike surface water, groundwater can move as slow as a meter per year.

This means it can take several thousands of years for underground aquifers to become replenished.

7 Major Difference between Infiltration and Percolation (explained)

7 Major Difference between Infiltration and Percolation (explained)

7 Major Difference Between Infiltration and Percolation

Compiled by Stanley Udegbunam || Dec 04, 2020

AFRILCATE 

OVERVIEW OF INFILTRATION AND PERCOLATION

Infiltration and Percolation are closely related since they both refer to the water flow through soil and rock cavities.

They are both intrinsic properties of geologic formations and also important processes of the water cycle.

Nevertheless, a clear distinction exists between these two terms.

We will start with their definitions, pin-point their disparities along the way, and conclude with a tubular representation of the differences.

Let’s begin with infiltration.

WHAT IS INFILTRATION?

Infiltration is the downward entry of water into the soil or rock surface.

When rain or snowmelt hits the ground, It may either infiltrate the soil or continue across the land as runoff.

Infiltration rate is a measure of the rate at which a particular soil is able to absorb water.

It is measured in inches per hour or millimeters per hour with an instrument called infiltrometer.

The maximum amount of rainwater that can enter a soil in a given time is called the soil’s infiltration capacity. When this maximum is reached, the soil becomes saturated.

Infiltration is a surface phenomenon therefore it is governed by soil surface conditions.

percolation vs infiltration

water infiltration occurs at the surface and subsurface level

WHAT IS PERCOLATION?

Percolation is the downward movement of water through soil or rock layers due to gravity and capillary forces.

After water infiltrates the soil surface, it continues to move downwards through different layers of the soil.

This internal downward movement through the soil layers is what is referred to as percolation and not the initial surface entry.

Hence, infiltration occurs on the soil surface, after which the water percolates downwards through the soil profile to the saturation zone.

Percolation rate is the speed at which that water moves through different soil layers. In other words, it’s the speed at which percolation occurs.

This speed can also be measured in inches per hour but with an instrument called Lysimeter.

Percolation is an important process required to replenish aquifers

They are different underground geologic formations but the aquifer is responsible for holding groundwater in the saturation zone.

infiltration and percolation difference

TABULAR DIFFERENCE BETWEEN INFILTRATION AND PERCOLATION

The table below groups the differences into key sections for easy understanding.

Differences
INFILTRATION

PERCOLATION
DEFINITION
Downward entry of water into the soil or rock surface.Downward movement of water through soil or rock layers
SPEED OF PROPAGATIONInitial surface infiltration occurs at a faster rate than percolation rate.Percolation occurs at a much slower speed.
SYMBOLInfiltration = (f)
Initial surface infiltration = (vo)
Maximum infiltration /Infiltration capacity = (fc)
Simply represented with the letter (P)
OCCURRENCEA surface and sub-surface phenomenon.An underground phenomenon.
MEASUSRING INSTRUMENT
Measured with an InfiltrometerDirect and accurate measurements is obtained using a Lysimeter.
IMPORTANCE
Replenishes soil water deficiency.Replenishes underground aquifers.
PRACTICAL APPLICATION
In the medical field, a procedure called Infiltration anesthesia is used for minor surgical and dental procedures.Common household application is the coffee Percolator.
A type of coffee maker in which hot water is forced, either by boiling action or pump, up into a filter basket that holds coffee grounds.
Differences
INFILTRATION

PERCOLATION
DEFINITION
Downward entry of water into the soil or rock surface.Downward movement of water through soil or rock layers
SPEED OF PROPAGATIONInitial surface infiltration occurs at a faster rate than percolation rate.Percolation occurs at a much slower speed.
SYMBOLInfiltration = (f)
Initial surface infiltration = (vo)
Maximum infiltration /Infiltration capacity = (fc)
Simply represented with the letter (P)
OCCURRENCEA surface and sub-surface phenomenon.An underground phenomenon.
MEASUSRING INSTRUMENT
Measured with an InfiltrometerDirect and accurate measurements is obtained using a Lysimeter.
IMPORTANCE
Replenishes soil water deficiency.Replenishes underground aquifers.
PRACTICAL APPLICATION
In the medical field, a procedure called Infiltration anesthesia is used for minor surgical and dental procedures.Common household application is the coffee Percolator.
A type of coffee maker in which hot water is forced, either by boiling action or pump, up into a filter basket that holds coffee grounds.

Despite the differences between infiltration and percolation, they are both required to recharge underground aquifers.

DO YOU KNOW?

Groundwater is the water present beneath the earth’s surface in soil pore spaces, underground bedrocks and in the fractures of rock formations.

It is different from surface water – water that exists on soil surfaces.

Groundwater accounts for approximately 30% of fresh water on earth.

DO YOU KNOW?

Groundwater is the water present beneath the earth’s surface in soil pore spaces, underground bedrocks and in the fractures of rock formations.

It is different from surface water – water that exists on soil surfaces.

Groundwater accounts for approximately 30% of fresh water on earth.

6 Major Difference between Porosity and Permeability – Afrilcate

6 Major Difference between Porosity and Permeability – Afrilcate

6 Major Difference Between Porosity and Permeability

Compiled by Stanley Udegbunam || Dec 03, 2020

AFRILCATE 

OVERVIEW OF POROSITY AND PERMEABILITY

Porosity and Permeability are two closely related terms to the extent that they are often confused for the other.

A clear difference exists between them therefore it is a wrong practice to use both terms interchangeably.

We will look at the disparities between both terms starting from their definitions and we will conclude with a tabular representation of the differences.

Let’s begin…

WHAT IS POROSITY?

Porosity refers to the amount of empty space within a given material.

These empty spaces are called pores and since they are void, the materials exhibits water holding capacity.

Therefore, we can define “rock porosity” (porosity of rock) as a measure of the ability of the given rock sample to hold fluid within its pore space.

This space can be between grains, cracks or within the cavity of rocks.

Deductively, we can also define porosity as the volume of empty spaces or pores relative to the total rock volume.

Porosity = (Volume of pore spaces / total rock volume) × 100%

It can be expressed as a percentage.

For most rocks, porosity varies from less than 1% to 40%.

Porosity is dependent upon factors like the size, shape, and aggregate packing of soil particles.

It’s also a good measure of the water holding capacity of the soil.

WHAT IS PERMEABILITY?

Permeability is a measure of the ease with which a fluid can move through porous rock. It refers to how connected pore spaces are to one another.

If the material has high permeability then the pore spaces are well connected allowing water to completely flow through.

However, if there is low permeability then the pore spaces are isolated and the water is trapped.

A rock may be extremely porous, but if the pores are not connected to one another, it will have no permeability.

Likewise, a rock may have just tiny pore openings indicating low porosity but if they are well connected, the rock becomes highly permeable despite their low porosity.

Rocks such as pumice and shale have high porosity, yet they are nearly impermeable (poorly interconnected voids).

Clay is also porous but it’s the least permeable due to its compact nature.

This explains why clay is usually referred to as an aquitard.

Aquitards are poorly permeable geologic formations that retard the flow of groundwater.

permeability vs porosity

Permeability – connected pore spaces

Some materials like gravel and sand are both porous and permeable, making them good aquifer materials.

If the soil is both permeable and porous, infiltration rate is increased and percolation to the water table is hastened.

Permeability is typically expressed in Darcy (d) and millidarcy (md)

porous vs  permeable

TABULAR DIFFERENCE BETWEEN POROSITY AND PERMEABILITY

The table below groups the differences into key sections for easy understanding.

Differences
POROSITY

PERMEABILITY
DEFINITION
A measure of the void space in a given material.A measure of the ease with which a fluid can move through a porous material.
MEASURING INSTRUMENTCan be measured using the Bendtsen Roughness / Smoothness TesterMeasured using Insitu borehole permeability testing or cone penetration tests.
SYMBOLDenoted with the Greek symbol (∅).Denoted with the letter (K).
EXAMPLEPumice is an extremely porous volcanic rock. Others include: limestone and dolomite.Sandstone, fractured igneous and metamorphic rocks.
FactorsDependent on grain size, shape and material composition.Dependent on grain size, pore fluid properties, void ratio, organic matter and adsorbed water.
UNITExpressed as a percentage (%)Expressed in Darcy(d) and millidarcy (md)
Differences
POROSITY

PERMEABILITY
DEFINITION
Amount of the void space in a given material.The ease with which a fluid can move through a porous material.
MEASURING INSTRUMENT
Can be measured using the Bendtsen Roughness / Smoothness TesterMeasured using Insitu borehole permeability testing or cone penetration tests.
SYMBOLDenoted with the Greek symbol (∅).Denoted with the letter (K).
EXAMPLEPumice is an extremely porous volcanic rock. Others include: limestone and dolomite.Sandstone, fractured igneous and metamorphic rocks.
FactorsDependent on grain size, shape and material composition.Dependent on grain size, pore fluid properties, void ratio, organic matter and adsorbed water.
UNITExpressed as a percentage (%)Expressed in Darcy(d) and millidarcy (md)

Despite the differences, porosity and permeability are both intrinsic properties of geologic materials.

DO YOU KNOW?

The study of the occurrence, distribution, movement and properties of water

on and beneath the earth surface is called hydrology.

DO YOU KNOW?

The study of the occurrence, distribution, movement and properties of water on and beneath the earth surface is called hydrology.

What is an Aquifer? Types and Importance (all Explained)

What is an Aquifer? Types and Importance (all Explained)

What is Aquifer? – Meaning, Types and Importance

Written by Stanley Udegbunam || Nov 29, 2020

AFRILCATE 

WHAT IS AN AQUIFER?

An aquifer is a body of porous rock or sediments saturated with groundwater.

Aquifers are both permeable and porous and made of unconsolidated materials like sand, gravel, and rocks that store and transmit water.

Fractured limestone and volcanic rocks such as columnar basalts also make good aquifers.

Rocks such as granite and schist are generally poor aquifers because they have very low porosity.

However, if these rocks are highly fractured, they will make good aquifers.

The study of water movement on and beneath the earth’s surface is called hydrology and one who studies hydrology is called a hydrologist.

But there’s another field of study that focuses on aquifers. It’s called hydrogeology.

Hydrogeology is the study of water flow in aquifers and the characterization of aquifers.

A practitioner of hydrogeology is called hydrogeologist.

One major difference between a hydrologist and hydrogeologist is that:

While hydrologist studies the occurrence and movement of both surface water and groundwater, hydrogeologist is focused only on water flow and distribution of groundwater which is the water stored and transported in aquifers.

HOW IS AN AQUIFER RECHARGED?

Surface water enters the aquifer as precipitates fall on the earth’s surface and seep through the soil.

This is possible due to the porosity of the soil, causing infiltration of the water content into the soil.

The water is further pulled down between the aggregate soil particles and this gives rise to water percolation.

A permeable soil will allow for faster water percolation since the pore spaces are connected together.

The combined process of infiltration and percolation is called recharge

Some types of soils allow more water to infiltrate than others depending on the soil’s characteristics.

During recharge, water is pulled down into the earth by gravity through two zones.

The upper zone, called the zone of aeration, is where a mixture of water and air fills the pore spaces.

Below the zone of aeration is the zone of saturation, where the pore spaces are completely filled by water.

The upper boundary of the zone of saturation is known as the water table.

Aquifers are found in the area saturated with water.

groundwater process

As the groundwater transcends to this region, the aquifers get recharged.

Unlike surface water, groundwater can move as slow as a meter per year. This means it can take several thousands of years for underground aquifers to become replenished.

Wells are drilled into the aquifer to pump out water to the earth’s surface.

When water is pumped from a well, the water table is generally lowered into a cone of depression at the well.

Groundwater normally flows down the slope of the water table to fill the void space in the well.

Nevertheless, if water is pumped from a well faster than it is replenished, the aquifer may go dry and the water table is lowered.

In such cases, the aquifer can be recharged through a man-made process known as artificial recharge

TYPES OF AQUIFERS

There are generally two types of aquifers:

  1. Unconfined Aquifer
  2. Confined Aquifer

1. What is an Unconfined Aquifer?

An unconfined aquifer has a layer of permeable material above it.

This allows water directly above its surface to seep into the aquifer.

The shallowest aquifer at a given location is mostly unconfined.

Unconfined layer simply means that the layer is not restrictive, a surface layer that allows easy passage of water and particles.

A good example is the Biscayne Aquifer.

In some cases, an unconfined aquifer is guarded by an aquitard.

Aquitards are porous layers that retards water flow into or out of the aquifer but still don’t prevent it.

This means that water will still get into an unconfined aquifer whether it’s guarded by an aquitard or not.

The only difference is that it will take a much longer time for the aquifer to be recharged if it has a layer of aquitard above it.

Unconfined aquifers are usually recharged by rain or stream water infiltrating directly through the overlying soil.

2. What is a confined Aquifer?

A confined aquifer is overlain by impermeable rock or clay which hinders the passage of water.

Confined aquifers could also be referred to as “Artesian aquifers”.

The confining layer offer some protection from surface contamination unlike the unconfined aquifer.

AQUIFER AND THE WATER CYCLE

In this section, we’ll look out how water stored in the aquifer finds it’s way back into the atmosphere to join the water cycle.

The water cycle describes the continuous movement or circulation of water in the earth-atmosphere system.

The outflow of water from aquifers occurs naturally to springs and river beds especially in cases where the groundwater pressure is higher than the atmospheric pressure in the vicinity of the ground surface.

The water content in springs and river beds then finds its way back to the atmosphere through evaporation from the water surface.

Groundwater is one of the most important sources of fresh water on earth.

Therefore, wells are drilled into aquifers and water is extracted to the earth’s surface where it’s used for various purposes like irrigation, industrial applications and consumption.

Water is lost from the plant to the atmosphere through transpiration or from the combined surrounding through evapotranspiration as well as other phase changes.

At this point, we all can agree that the aquifers are indispensable contributors to the water cycle.

FREQUENTLY ASKED QUESTIONS ON AQUIFERS

Stanley Udegbunam

I have compiled various frequently asked questions across the web to give you a clearer understanding of aquifers.

Without further ado, let’s get started✨

1. Is an aquifer an underground River or lake?

No. It’s just a common misconception. Groundwater seeps slowly into and out of aquifers, the process can never be fast to be compared to the flows of a river or lake.

2. What makes groundwater clean?

Aquifers acts as a natural filter for groundwater by forcing it to pass through small pores and between tight layers.

Dirt and particles are trapped as water seeps through the aquifer serving as a means of natural purification for groundwater.

3. How is an aquifer contaminated?

Aquifers are contaminated through wrongly managed man-made activities like septic tank leaks, excessive spray of pesticides and herbicides, improper lined landfills and deliberate disposal of toxic materials on the soil.

4. What aquifer type do you think is in more danger of contamination?

Unconfined aquifer is easily contaminated because it has is no restricting or confining layer.

Water seeps into unconfined aquifer easily and directly from the earth surface placing it at a higher risk for contamination.

5. Which aquifer would you want to drill into for a drinking water well?

The confined aquifer is better for drilling a drinking water well. Since confined aquifers are overlain by impermeable materials, it serves as a protective coating making it difficult to get contaminated by bacteria and dirt particles.

Unconfined layer allows easy passage of particles and water making it less suitable for drilling a drinking water well.

DO YOU KNOW?

Soil Porosity and Permeability are two different soil characteristics that affect recharge rate.

Porosity refers to the amount of empty pore spaces within a given material.

While permeability is a measure of the ease with which a fluid can move through porous rock.

DO YOU KNOW?

Soil Porosity and Permeability are two different soil characteristics that affect recharge rate.

Porosity refers to the amount of empty pore spaces within a given material.

While permeability is a measure of the ease with which a fluid can move through porous rock.

Artificial Groundwater Recharge -The Best Explanatory Guide

Artificial Groundwater Recharge -The Best Explanatory Guide

ARTIFICIAL GROUNDWATER RECHARGE – Explanatory Guide

Compiled by Stanley Udegbunam || Nov 26, 2020

AFRILCATE

OVERVIEW OF ARTIFICIAL GROUNDWATER RECHARGE?

Groundwater is the largest source of freshwater for mankind and approximately 30% of the freshwater on Earth is groundwater.

In some rural areas, groundwater accounts for 100% of resident’s drinking water.

Groundwater is replenished naturally at a very slow rate. It can take several thousands of years for water to infiltrate the soil surface and percolate to the saturation zone.

In areas where groundwater is utilized faster than its natural replenishing rate, man-made recharge method becomes a necessary option for balancing the water levels.

This man-made recharge means is what is termed artificial groundwater recharge.

Artificial groundwater recharge is popularly called “artificial recharge”.

So for this guide, we’ll refer to artificial groundwater recharge as just artificial recharge.

Shortage of groundwater in an area will lead to depletion of aquifers and dryness of wells.

Its adverse effects will be felt both on the inhabitants and the environment.

WHAT IS ARTIFICIAL RECHARGE?

Artificial recharge is the process of increasing the amount of water that enters an aquifer through planned, human-controlled means.

Artificial recharge is different from the natural recharge means where precipitates like rainfall and snowmelt infiltrate the soil and percolate downwards to the water table without purposed human intervention.

Groundwater Recharge is the primary method through which water enters underground resources like the aquifer.

Aquifers are underground layers of rocks that hold the groundwater and they are found in the saturation zone.

A reduction in groundwater recharge rate will lead to a reduced amount of water stored in the aquifers which will negatively affect the ecosystem. 

artificial groundwater recharge
Artificial recharge of groundwater is beneficial in two major cases:

  1. when the natural recharge can’t balance water levels due to reduced availability of surface water.
  2. In areas where the consumption rate exceeds the natural recharge rate.

In the next sub-heading, we’ll look at the various methods in which aquifers can be artificially recharged.

METHODS OF ARTIFICIAL RECHARGE

Artificial recharge methods can be classified into two broad groups:

  1. Direct Methods
  2. Indirect Methods
Direct methods are subdivided into:

  1. Surface Spreading Techniques
  2. Sub-surface Spreading Techniques

a. Surface Spreading Techniques

  • Basins or percolation tanks
  • Ditch and furrow system
  • Stream augmentation
  • Flooding
  • Over irrigation

b. Sub-surface Techniques

  • Injection or recharge wells
  • Recharge pits and shafts
  • Borehole flooding
  • Dug well recharge
  • Natural openings, cavity fillings.
Indirect methods are subdivided into:

  1. Induced Recharge
  2. Aquifer Modifications
  3. Groundwater Conservation Structures

a. Induced Recharge

  • Pumping well
  • Collector well
  • Infiltration galleries

b. Aquifer Modifications

  • Bore blasting
  • Hydro fracturing

c. Groundwater  Conservation structures

  • Groundwater dams
  • Fracture sealing

Of all techniques mentioned above, the most commonly used technique for the artificial recharge  of  groundwater is infiltration basins and Injection wells

artificial groundwater recharge techniques

Artificial Recharge Methods

ARTIFICIAL RECHARGE STRUCTURES

Some man-made structures for the artificial recharge of groundwater include:

  1. Percolation tanks
  2. Infiltration Basins
  3. Dug Wells
  4. Recharge Shafts
  5. Injection Wells

1. Percolation Tanks

Percolation tanks are popular structures used for groundwater recharge.

These are generally constructed across streams and submerges a land area in order to impound a part of the surface or run-off water.

The idea size of the percolation tank must be governed by its capacity of strata in tank bed.

Usually, percolation tanks are designed for storage capacities of 0.1 to 0.5 MCM and a ponded water column should be generally between 3 & 4.5m.

Groundwater Percolation tanks

Percolation tank in Satara district in Maharashtra, India.

2. Infiltration Basins

These structures are used to recharge the groundwater reservoir both in loose soil as well as hard rock formation.

The efficacy and feasibility of this structure is higher in hard rock formation where the rocks are highly fractured and weathered.

Artificial Recharge methods

Rapid Infiltration basins, Orlando, Florida

artificial recharge structures

Phoenix–Avondale Water Partnership (to put colorado river into natural underground aquifers)

3. Dug Wells

In loose sediments as well as hard rock areas, there are thousands of dug wells that have either gone dry or the water levels have declined considerably.

These dug wells can be used as structures for artificial recharge.

The groundwater reservoir, stormwater, tank water, canal water, etc can be diverted into these structures to directly recharge the dried aquifer.

Dug well for artificial groundwater recharge

Dug Well Recharge

4. Recharge Shaft

This structure is very similar to a recharge pit but much smaller in cross-section.

Recharge shaft is used when the aquifer is located deep below the ground surface and overlain by poorly permeable strata.

Groundwater Recharge shaft

Recharge Shaft work at Gudarkheda village Ratlam MP for UNDP

5. Injection Wells

These structures are similar to a tube well but with the purpose of augmenting the groundwater storage of a confined aquifer by pumping in treated surface water under pressure.

The injection wells are advantageous when land is scarce.

Artificial recharge wells

Dug well: image source – Engineering Civil

IMPORTANCE OF ARTIFICIAL RECHARGE

The importance of artificial groundwater recharge schemes are listed below:

  • To augment the groundwater resources.
  • To store the surplus surface water particularly during the flood periods for future uses and reduce the flood peaks.
  • To retard the surface runoff resulting in lowering of flood peak, conserving the soil by reducing soil erosion and improving the soil moisture retention for a longer period in order to facilitate crop production and plant growth.
  • To improve the quality of water stored.
  • When the source water passes through the soil profile during the process of recharge, the soil mantle acts as a membrane to the travel of pathogens contained in the source water.
  • To conserve the groundwater at the point of use. This is particularly suited to hard rock areas.
  • To conserve thermal energy.
  • To prevent saline intrusion in coastal aquifers.

DO YOU KNOW?

Soil Porosity and Permeability are two different soil characteristics that affect recharge rate.

Porosity refers to the amount of empty pore spaces within a given material.

While permeability is a measure of the ease with which a fluid can move through porous rock.

DO YOU KNOW?

Soil Porosity and Permeability are two different soil characteristics that affect recharge rate.

Porosity refers to the amount of empty pore spaces within a given material.

While permeability is a measure of the ease with which a fluid can move through porous rock.

What is Groundwater Recharge? Types and Factors (explained)

What is Groundwater Recharge? Types and Factors (explained)

What is Groundwater Recharge? – Meaning, Types, Factors and Importance

Compiled by Stanley Udegbunam || Nov 26, 2020

Before talking about groundwater recharge, Let’s have a quick overview of what the term “groundwater” really means.

Groundwater is water present beneath Earth’s surface in soil pore spaces, underground bedrocks and in the fractures of rock formations.

It’s different from surface water which is basically water that exists on earth’s surfaces like streams and rivers.

Let’s proceed..

AFRILCATE 

WHAT IS GROUNDWATER RECHARGE?

Groundwater recharge is the process where surface water or precipitations infiltrates the soil and percolates downwards to the water table.

Groundwater Recharge is the primary method through which water enters underground resources like the aquifer.

TYPES OF GROUNDWATER RECHARGE

Groundwater recharge occurs in two forms:

  1. Natural Groundwater recharge
  2. Artificial Groundwater recharge

1. Natural Groundwater Recharge

    Groundwater is recharged naturally through:

    • precipitation ie. rainfall and snowmelt and
    • to a smaller extent by surface water like rivers and lakes.

    The water is able to move underground through the rock and soil due to connected pore spaces.

    This downward movement of water through different soil layers is called percolation.

    Some types of soils allow more water to infiltrate than others depending on the soil’s permeability.

    During natural recharge, water is first pulled into the zone of aeration; where a mixture of water and air fills the pore space.

    Then the water further travels downwards to the zone of saturation – where the pore spaces are completely filled by water.

    The upper boundary of the zone of saturation is known as the water table.

    Aquifers are the underground layers of rocks that hold the groundwater and they are found in the saturation zone.

    Groundwater Recharge Types

    Groundwater is recharged naturally through the infiltration of rain water on the soil surface.

    Groundwater can move as slow as a meter per year.

    This means it can take several thousands of years for underground aquifers to become replenished.

    2. Artificial Groundwater Recharge

    In areas where groundwater is utilized faster than its natural replenishing rate, man-made recharge method becomes a necessary option for balancing the water levels.

    Artificial recharge is the process of increasing the amount of water that enters an aquifer through planned, human-controlled means.

    Groundwater can be artificially recharged by redirecting water across the land surface through canals, infiltration basins, or ponds; adding irrigation furrows or sprinkler systems; or simply injecting water directly into the subsurface through injection wells.

    artificial recharge

    Recharge Basins for Artificial Groundwater Recharge – A Central Avra Valley Storage and Recovery Project (CAVSARP)

     

    FACTORS AFFECTING GROUNDWATER RECHARGE

    Groundwater recharge depends on several factors such as:

    1. Porosity and Permeability of the soil
    2. infiltration capacity
    3. Precipitation rate
    4. climate changes.
    5. Type of vegetative cover
    recharging groundwater

    Irrigation also affects groundwater recharge because leached irrigation water seeps down through soil openings.

    If farmland irrigation decreases due to reduced availability of surface water then, groundwater recharge via leached irrigation water reduces also.

    Climate change is likely to have a strong impact on coastal saltwater intrusion as well as on salinization of groundwater.

    IMPORTANCE OF GROUNDWATER RECHARGE

    Groundwater is the largest source of freshwater for mankind and approximately 30% of the freshwater on Earth is groundwater. In some rural areas, groundwater accounts for 100% of the resident’s drinking water.

    It is also an integral part of the water cycle. The importance of groundwater recharge cannot be over-emphasized.

    For sustainable groundwater management, groundwater recharge is required to balance environmental water levels and also maintain flow into rivers, lakes and wetlands.

    Shortage of groundwater in an area will lead to depletion of aquifers and dryness of wells. Its adverse effects will be felt both on the inhabitants and the environment.

    According to wiki, artificial groundwater recharge is becoming increasingly important in India, where over-pumping of groundwater by farmers has led to underground resources becoming depleted.

    Less groundwater recharge leads to a drop in the groundwater table, which can have a negative impact on vegetation.

    natural water recharge importance

    DO YOU KNOW?

    Soil Porosity and Permeability are two different terms.

    Porosity refers to the amount of empty pore spaces within a given material. 

    While permeability is a measure of the ease with which a fluid can move through porous rock.

    DO YOU KNOW?

    Soil Porosity and Permeability are two different terms.

    Porosity refers to the amount of empty pore spaces within a given material.

    While permeability is a measure of the ease with which a fluid can move through porous rock.

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