Sustainable Water Management

Sustainable water management means using water in a way that leaves enough for tomorrow. This lesson for Classes 3 to 5 explains where our water comes from, why wells and taps can run dry, and how rainwater harvesting, drip irrigation and reusing water help. It also looks at stepwells and johads, and links to a worksheet of Olympiad practice questions.

• What Does Sustainable Water Management Mean?
• Where Does Our Water Come From?
• Why Can Water Run Short?
• Catching the Rain: Rainwater Harvesting
• Smart Watering on Farms and in Gardens
• Using Water Twice
• What India Learned Long Ago
• What You Can Do at Home and at School

What Does Sustainable Water Management Mean?

Turn on the tap in your kitchen. Water comes out. Have you ever wondered how it got there, and whether it will always be there?

For many families in India, the answer is not so simple. In summer, the taps in some homes run dry, and people wait for a water tanker to come. Borewells that gave plenty of water a few years ago now give very little.

Sustainable water management means using and looking after water so that there is enough for us today and for the people who come after us. It has two parts. The first part is taking less, which means not wasting the water we have. The second part is giving back. We help rainwater return to the ground, the lakes and the rivers, and we keep that water clean.

Think of a piggy bank. If you keep taking out more coins than you put in, one day it will be empty. Our water supply works in the same way.

Where Does Our Water Come From?

Almost all the water on Earth is in the oceans, and it is salty. About 97 out of every 100 litres of Earth's water is seawater. We cannot drink it, and most crops cannot grow with it.

Most of the fresh water that is left is frozen in glaciers and ice sheets, or lies deep under the ground. Only a very small part is in rivers, lakes and ponds, where we can reach it easily.

This fresh water keeps getting refilled by the water cycle:

• Evaporation: The Sun heats the water in seas, lakes and rivers. Some of it turns into water vapour and rises into the air.
• Condensation: High up, the vapour cools and turns into tiny droplets. These droplets form clouds.
• Precipitation: When the droplets join and grow heavy, they fall as rain, snow or hail.
• Collection: Rainwater flows into rivers and lakes, and some of it soaks into the soil.

The water that soaks down fills the tiny gaps between grains of sand, gravel and rock under the ground. This is called groundwater. The underground layer that holds it is called an aquifer. A hand pump, a well or a borewell pulls up groundwater. When rain soaks into the ground and adds to this hidden store, we call it groundwater recharge.

Why Can Water Run Short?

Rain falls every year. So why do wells dry up? Most of the reasons have to do with the way people use land and water.

• We pump faster than the rain can refill. In many places, borewells pull out water every day. If more water comes out of the ground than goes in, the water level under the ground keeps falling. Wells then have to be dug deeper and deeper.
• Concrete covers the ground. Rain cannot soak through roads, paved yards and rooftops. It rushes into drains instead, and the ground below stays dry.
• Water gets dirty. When sewage and garbage go into a river, the water is still there, but it is no longer safe to use.

Who do you think uses the most fresh water: homes, factories or farms? Around the world, it is farms. They use more fresh water than homes and factories put together. Crops such as rice and sugarcane need a lot of water. So saving water on farms makes a very big difference.

Catching the Rain: Rainwater Harvesting

Picture your school building during a heavy monsoon shower. Water pours off the roof, runs across the playground and out of the gate into the drain. An hour later, it is gone.

Rainwater harvesting means collecting that rain and saving it, instead of letting it run away. A simple rooftop system works like this:

1. Rain falls on a clean roof.
2. Pipes carry the water down from the roof.
3. The water passes through a filter, such as a mesh or layers of sand and gravel, which removes leaves and dirt.
4. The water is stored in a tank for later use, or it is sent into a recharge pit or an old well so that it can soak into the ground.

A recharge pit is a hole in the ground filled with layers of big stones, smaller pebbles and coarse sand. Rainwater trickles down through these layers, gets cleaned a little on the way, and reaches the groundwater.

Stored rainwater is good for watering plants, washing floors and flushing toilets. If it is going to be used for drinking, it must first be filtered and boiled or treated properly.

Tamil Nadu was one of the first states in India to make rooftop rainwater harvesting compulsory for buildings. Today, many cities ask new buildings to include it.

Smart Watering on Farms and in Gardens

When a field is flooded with water, a lot of it never reaches the roots of the crop. It dries up in the hot sun or runs off the edges of the field, and the weeds drink their share too.

Drip irrigation fixes this problem. Thin pipes with tiny holes run along the rows of plants, and water drips slowly right at the roots. Very little is lost. Sprinkler irrigation sprays water over the crop like gentle rain. It also uses less water than flooding a field.

You can use the same ideas for a garden at school or a few pots on your balcony:

• Water plants early in the morning or in the evening. The Sun is not strong then, so less water evaporates.
• Pour water at the base of the plant, near the roots, not over the leaves.
• Cover the soil around plants with dry leaves or straw. This covering is called mulch. It keeps the soil cool and damp for longer.

Using Water Twice

When someone at home washes rice or vegetables, where does that water go?

In most homes, it goes straight down the sink. But that water is only a little dirty. It can easily be used to water the plants.

Water that has already been used for washing hands, bathing, washing clothes or cleaning vegetables is called greywater. Water from toilets is called blackwater. Blackwater carries germs and must never be reused at home.

Some easy ways to use water twice:

• Water the plants with the water left after washing rice, dal and vegetables.
• Many RO water purifiers let out a stream of waste water while they clean drinking water. Collect it in a bucket and use it to mop the floor or wash a car.

Towns and cities reuse water on a much larger scale. Used water from homes travels through sewer pipes to a sewage treatment plant. There, most of the dirt and germs are taken out. The cleaned water can then be safely let into a river, or used again for parks, building work and factories.

What India Learned Long Ago

People in India have been saving rainwater for hundreds of years. They did this most of all in dry places such as Rajasthan and Gujarat, where rain falls for only a few months of the year.

• Stepwells, called baoli or vav, are deep wells with steps leading down to the water. People could still reach the water when its level dropped in summer. Rani ki Vav in Patan, Gujarat, is a famous stepwell and a UNESCO World Heritage Site.
• Johads are small mud walls built across slopes in Rajasthan to hold back rainwater. The water stays behind the wall long enough to soak into the ground and fill up the wells nearby. In Alwar district, villagers worked with a group called Tarun Bharat Sangh to repair old johads and build new ones. Over the years, the Arvari river, which used to stay dry for most of the year, began to flow all year round.
• Tankas are covered underground tanks used in the Thar desert. Some similar ones are called kunds. Rain from a roof or a courtyard flows into them, and families use the stored water for months.

The same old idea is behind a national campaign today. The Government of India's Jal Shakti Abhiyan: Catch the Rain asks people to "catch the rain, where it falls, when it falls". It encourages towns and villages to build tanks, recharge pits and check dams before the monsoon arrives.

What You Can Do at Home and at School

You do not need a big project to manage water well. A few small habits, done every day by everyone at home, save a lot of water over a year.

• Turn off the tap while you brush your teeth or soap your hands.
• Take a bucket bath instead of a long shower.
• Wash a car or a bicycle with a bucket and a cloth, not a running hose.
• Tell an adult as soon as you spot a leaking tap or an overflowing tank.
• Never throw wrappers, plastic or cooking oil into drains, ponds or rivers.
• Find out if your school collects rain from its roof. If it does not, a recharge pit near the playground is a great idea to suggest to your teacher.

Try this: Find a tap that drips. Put a measuring jug under it for one hour and note how much water collects. Multiply that by 24 to find out how much is lost in a whole day. The total is usually much bigger than you would guess. Use the collected water for your plants, and ask an adult to get the tap fixed.

Want to test yourself? Try the 10 questions in the Sustainable Water Management worksheet, or read about the International Green Warrior Olympiad.