Water Usage and Sources

Water is essential for life and for a vast number of our daily activities. Apart from drinking, we use water for cooking, cleaning utensils, washing clothes, and bathing. A severe scarcity of water, even for a week, would make these basic activities impossible and disrupt our lives completely.

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How Much Water Do We Use?

The quantity of water we use each day is often much larger than we realize. By measuring the water used for various activities, we can get an idea of our family's daily and yearly water consumption.

Activity	Amount of water used (in Litres)
Drinking
Brushing
Bathing
Washing utensils
Washing clothes
Toilets
Cleaning floor
Any other
Total water used in a day by a family

Beyond our direct daily activities, water is crucial for producing almost everything we use. It is needed in large quantities to grow crops like wheat, rice, and pulses, as well as plant fibres like cotton. Industries also require a significant amount of water to manufacture goods. For example, it takes about two glasses of water to produce a single page of a book.

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Where Do We Get Water From?

The water that reaches our homes through taps is drawn from sources like lakes, rivers, ponds, or wells. This water is then supplied through a network of pipes. Ultimately, all the water we use comes from these natural sources.

But where does the water in these sources come from? The Earth's surface is about two-thirds covered with water, most of which is in oceans and seas. However, this water is saline (salty) due to many dissolved salts, making it unfit for drinking, agriculture, or industrial use. Despite this, the oceans play a vital role in supplying the fresh water we use. The process that makes this possible is the water cycle.

The Water Cycle: From Earth to Air

The continuous movement of water from the Earth's surface to the atmosphere and back again is known as the water cycle. This cycle is responsible for replenishing freshwater sources on land.

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Evaporation: The Disappearing Trick of Water

Have you noticed that water spilled on a floor or in wet clothes seems to disappear as it dries? This happens because the water changes from its liquid form into a gaseous form called water vapour. This process is called evaporation.

Heat is essential for evaporation. The main source of heat for this process is the sunlight. During the day, sunlight heats the water in oceans, seas, rivers, lakes, and ponds, causing it to evaporate continuously. When salt water evaporates, the salt is left behind, and only pure water turns into vapour. Evaporation also occurs from the soil and other land areas. It takes place faster in sunlight but also happens in the shade, where the heat is provided by the warm surrounding air.

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Transpiration: Loss of Water by Plants

Plants absorb water from the soil through their roots. They use a part of this water to prepare their food through photosynthesis and retain some in their parts. The remaining excess water is released by the plants into the air as water vapour. This process is called transpiration.

A significant amount of water is lost through transpiration. For example, wheat plants that produce one kilogram of wheat release nearly 500 litres of water through transpiration. Both evaporation and transpiration add water vapour to the air.

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Condensation: How Clouds are Formed

The water vapour that enters the air is not lost forever; it comes back to us through the process of condensation.

Condensation is the process of conversion of water vapour back into its liquid form. You can observe this when tiny water droplets form on the outer surface of a glass containing ice-cold water. The cold surface of the glass cools the air around it, causing the water vapour present in the air to condense and form these droplets.

As we go higher from the Earth's surface, the air gets cooler. When air containing water vapour rises, it cools down. At sufficient heights, the air becomes so cool that the water vapour condenses to form tiny droplets of water. These droplets are so light that they remain floating in the air and appear to us as clouds.

Back to the Oceans: The Journey of Water

The water cycle is completed when the water that went into the air as vapour returns to the Earth's surface. Many water droplets in the clouds come together to form larger, heavier drops of water. When these drops become too heavy to float, they begin to fall. This falling of water drops is what we call rain. In special conditions, it may also fall as hail or snow.

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The Return Path to the Oceans

Most land surfaces are above sea level. Therefore, most of the water that falls on land as rain or snow eventually makes its way back to the oceans. This happens in several ways:

• Snow on mountains melts into water, which flows down as streams and rivers.
• Rainwater also flows in the form of streams and rivers. Most rivers travel long distances and ultimately fall into a sea or an ocean.
• Rainwater also fills up lakes and ponds.

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Groundwater

A significant part of the rainwater seeps into the ground. This process is called infiltration. This water that gets collected under the ground is known as groundwater. Groundwater is a very important source of fresh water for us.

• It feeds open wells and many lakes.
• It is drawn out using handpumps and tubewells.

Overuse of groundwater is a major concern. The more handpumps and tubewells are used in an area, the deeper we need to dig to find water, leading to a worrisome decrease in the groundwater level.

Seepage of rainwater into the ground is also affected by land use. In areas with little or no vegetation, rainwater flows away quickly, carrying the topsoil with it. Land covered with concrete roads and buildings significantly reduces the seepage of water into the ground, which affects the availability of groundwater.

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Summary of the Water Cycle

The circulation of water from the ocean and land to the air and back to the land and oceans is a continuous process known as the water cycle. It can be summarized as follows:

1. Water from oceans, lakes, and rivers goes into the air as vapour through evaporation. Plants also release water vapour through transpiration.
2. This water vapour rises, cools, and forms clouds through condensation.
3. The water then returns to the Earth as rain, hail, or snow (precipitation).
4. Finally, this water flows over the land and through rivers back to the oceans, completing the cycle.

This cycle ensures a continuous supply of fresh water on land.

The Effects of Rainfall: Floods and Droughts

The amount, timing, and duration of rainfall vary greatly from place to place. While rain is essential for life, too much or too little of it can cause serious problems.

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What if it Rains Heavily? - Floods

In our country, most rainfall occurs during the monsoon season, which brings relief from summer heat and is crucial for sowing many crops. However, excessive rainfall can lead to many problems.

Heavy rains can cause the water level in rivers, lakes, and ponds to rise dangerously. This water may then spread over large areas, causing floods. Floods can submerge crop fields, forests, villages, and cities, leading to extensive damage to:

• Crops and domestic animals
• Property and infrastructure
• Human life

During floods, animals living in the water get carried away, while those living in the soil and on land can get trapped and die.

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What Happens if it Does Not Rain for a Long Period? - Droughts

If it does not rain in a region for a year or more, the consequences can be equally devastating. The soil continuously loses water through evaporation and transpiration, but it is not replenished by rain.

This leads to a condition called drought. In drought conditions:

• The soil becomes dry.
• The water level in ponds and wells goes down, and some may even dry up completely.
• Groundwater becomes scarce.
• It becomes difficult to get food for humans and fodder for animals.

Droughts cause immense hardship for people, animals, and the vegetation in the affected areas.

Water Conservation and Rainwater Harvesting

Only a very small fraction of the water available on Earth is fresh and fit for use by plants, animals, and humans. Although the total amount of water on Earth remains the same, the water available for our use is limited and is decreasing due to overuse.

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How Can We Conserve Water?

The demand for water is increasing day by day due to a rising population and increased use in agriculture and industries. This is leading to water shortages in many parts of the world. Therefore, it is very important that we use water carefully and take care not to waste it.

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Rainwater Harvesting

One effective way to increase the availability of water is to collect and store rainwater for later use. This practice is called rainwater harvesting. The basic idea is simple: “Catch water where it falls.”

Instead of letting rainwater, especially in urban areas with concrete surfaces, flow into drains and away to distant rivers, we can use techniques to capture it.

Techniques of Rainwater Harvesting

1. Rooftop Rainwater Harvesting: In this system, rainwater from a rooftop is collected and channelled through pipes to a storage tank. This water can be filtered and used directly. Alternatively, the pipes can lead the water into a pit in the ground, allowing it to seep into the soil and recharge the groundwater.
2. Roadside Drain Harvesting: Another option is to design roadside drains in a way that allows the collected rainwater to go directly into the ground, rather than being carried away. This also helps in recharging the groundwater.

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