What is Groundwater?
Water is the basis of life. We know that the earth is full of water, i.e. about 50 to 80 % of our bodies are made of water depending on age, and 70% of the earth’s surface is covered by water, and only 3 % of it is fresh water; however, there’s a lot more to water than all this blue stuff we see on the globe.
The water we can see on the surface of the earth is the surface water, e.g. a lake, pond river stream, and the ocean, and the water found in the ground below our feet is the groundwater.
The groundwater is the water that’s crammed into the tiny gaps between rocks soils and sediments underground.
A full body of the groundwater is called an aquifer.
Types of Groundwater
There are three types of groundwater:
Conventional
Coastal
Karst groundwater systems
Aquifers
Let’s understand the aquifers through a real-life example.
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When you push the handle of a handpump, you might wonder where the water is coming from?
Here, this handpump pumps the groundwater.
The process by which water passes down through soil is called the infiltration. This infiltrated water gathers deep underground at the point where a layer of impermeable rocks is present.
These impermeable layers of rocks don’t allow the further passage of water through them, and these layers are called the aquifers.
Because of the infiltration of rainwater or water from other resources, it passes through the porous soil and “recharges” the groundwater. This water in the aquifer is what is pumped out using this handpump.
Groundwater Flow
You might have been driving across the country and seen water towers that are upon pedestals like you look in the picture below:
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You might be wondering what could be the purpose of these water towers?
Well, the purpose of them is to help give high water pressure in flat areas.
Let’s take this water tank here:
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The water will help you give high-pressure so that on the second-story of this apartment building will be able to take a nice strong shower.
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If we look at the lake, the water remains at the same level because the property of water is to be flat.
Now, if we look at Fig, the two containers are interconnected with pipes here, and there is a difference in the water levels in them.
Let’s consider a particular water molecule getting pushed by all of the water that’s at the top of the container A, and then the pressure inside the container is pushing down this water molecule which, in turn, pushes all the other water molecules in the line and we have this interconnected chain of pushing. This phishing stops as soon as the water comes at the same level.
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Similarly, in Fig, when the water tower is half full, then the pressure between the water molecules pushes against each other till the water in the tower and the pipes get connected to the apartment bedside that is at the same height. This way water flows up to the pipes of the second-story of the house.
Define Groundwater Recharge
We define groundwater recharge as the water added to the aquifer through the unsaturated zone following the percolation (or infiltration) after any storm rainfall event.
Types of Groundwater Recharge
Artificial Recharge of Groundwater
It can be defined as the practice of artificially increasing the amount of water that enters a groundwater reservoir.
It has an application in waste disposal, secondary oil recovery, land subsidence problems, and water supply problems.
Subsurface Groundwater Recharge
These systems are widely used in the agricultural area where waterlogging, and salinity problems are the main concern. They can also help in increasing the potential for infiltration.
Methods of Groundwater Recharge
There are various methods of groundwater recharge; some of them are discussed below:
Farm Ponds
They act as an effective source of water harvesting in the form of storage to reduce the water crisis in the country.
Check Dams
They are small, temporary dams constructed across a waterway or a drainage ditch to counteract erosion by reducing the speed of water flow.
Groundwater Pollution
Groundwater pollution or groundwater contamination occurs because of human activities, leading to various impacts on the environment.
Some Examples of Groundwater Pollution Are
The presence of a high level of hydrogen sulfide (H2S) in water
It may cause dizziness and severe headache.
The building of Radon gas in water
It increases the risk of cancer in humans.
High-level of Arsenic
It may lead to lung cancer in humans.
Chromium VI presence
Increases the risk of cancer in humans and animals
Degreasers and cleaners
They may cause problems like:
Nervous and respiratory damage.
Chemical burns
Digestion problems
6. Too much brininess
Leading to the widespread death of aquatic animals.
7. Dry cleaning fluid
Leading to the increase of risk cancer.
FAQs on Groundwater
1. What is groundwater and where is it found?
Groundwater is the water that exists beneath the Earth's surface, stored in the cracks and spaces in soil, sand, and rock. Unlike surface water in lakes and rivers, this water is not visible. It is the water that is drawn up through wells and handpumps, and it constitutes a significant portion of the world's freshwater supply.
2. What is the difference between groundwater and surface water?
The primary difference is their location. Surface water is found on the Earth's crust in rivers, lakes, and oceans. Groundwater is located underground in saturated zones. Generally, groundwater is cleaner and less prone to evaporation, but it is also slower to replenish compared to surface water sources.
3. What is an aquifer and how does it store water?
An aquifer is an underground layer of water-bearing permeable rock, rock fractures, or unconsolidated materials like gravel, sand, or silt. It acts like a natural underground reservoir. Water from precipitation seeps down through the soil in a process called infiltration and collects in these layers, held in place by an underlying layer of impermeable rock.
4. How does rainwater become groundwater?
Rainwater becomes groundwater through a process called groundwater recharge. When rain falls, some of it seeps into the ground, passing through the porous layers of soil and rock. This downward movement is known as percolation. The water continues to travel down until it reaches the zone of saturation, adding to the existing body of groundwater.
5. Why is it important to manage and recharge groundwater?
Managing and recharging groundwater is crucial for water sustainability. Constant extraction for agriculture and daily use can deplete aquifers faster than they can naturally refill. Artificially recharging groundwater helps to:
- Maintain the water level in wells and borewells.
- Prevent land subsidence (sinking of the ground).
- Support rivers and wetlands that rely on groundwater during dry seasons.
- Ensure a reliable water supply during droughts.
6. What are the common causes of groundwater pollution?
Groundwater pollution primarily occurs due to human activities. Contaminants seep into the ground and mix with the water in aquifers. Common causes include:
- Leakage from industrial waste sites and landfills.
- Runoff from agricultural fields containing pesticides and fertilisers.
- Contamination from poorly maintained septic systems.
- Seepage of harmful chemicals like arsenic, chromium, and degreasers into the soil.
7. Is groundwater naturally safe to drink without any treatment?
Not always. While the ground acts as a natural filter, groundwater is not guaranteed to be pure. It can contain harmful dissolved minerals like arsenic or be contaminated with bacteria, viruses, and chemicals from pollution. Therefore, it is often necessary to test and treat groundwater to ensure it is safe for consumption, as per health guidelines.
8. How can over-extraction of groundwater cause serious environmental problems?
Over-extraction, or pumping out groundwater faster than it is replenished, leads to severe consequences. The most significant problems include the lowering of the water table, causing wells to dry up. In coastal regions, it can lead to saltwater intrusion, making freshwater salty and unusable. Furthermore, it can cause the ground to compact and sink, a phenomenon known as land subsidence, which can damage buildings and infrastructure.
