Where Rain Comes From

Water goes round and round

Where does rain come from? And where does it go after it falls?

The answer is surprising. The water that falls on your roof today is very old. It has been rain before, many, many times. It has been in the sea, in a cloud, in a river, maybe even in an elephant at Mole.

Water on Earth does not get used up. It moves in a big circle, from the ground to the sky and back again. We call this circle the water cycle.

In this book you will learn the four parts of the cycle: evaporation, condensation, precipitation and collection. Those are big words, but the ideas are simple.

The three forms of water

Water can be three things.

Liquid: water you can pour. Rain, rivers, the sea, sachet water.

Gas: water vapour. It is invisible. It is in the air around you right now, even though you cannot see it.

Solid: ice. Water that is frozen hard. Ice cubes, the ice in a cold store, hailstones.

Water changes from one form to another when it gets hotter or colder.

• Heat liquid water → it becomes vapour (gas).
• Cool vapour → it becomes liquid again.
• Freeze liquid → it becomes ice (solid).

The water cycle is really about water changing between liquid and gas, over and over.

Try this: Name one place you have seen water as a liquid, as a gas and as a solid.

The whole cycle in one picture

Look at the picture. It shows the water cycle.

1. The sun heats the sea, lakes and rivers. Water rises into the air as vapour. This is evaporation.
2. High up, the air is cold. The vapour turns back into tiny drops and makes clouds. This is condensation.
3. The drops join together and get heavy. They fall as rain. This is precipitation.
4. The rain runs into streams, rivers, lakes and the sea, or sinks into the ground. This is collection.

Then the sun heats the water again, and the cycle starts over. It never stops.

Try this: Point to each of the four stages in the picture and say its name out loud.

Stage 1: Evaporation

Evaporation is when liquid water turns into water vapour and rises into the air.

The sun is the engine. Its heat warms the water in the sea, Lake Volta, rivers, ponds and even puddles. The warm water slowly turns into vapour and floats up.

You cannot see it happening, but you can see the result. After rain, a puddle on the school compound gets smaller and smaller until it is gone. Where did the water go? Into the air!

Wet clothes on the line dry the same way. The sun and the wind turn the water into vapour.

Try this: Pour a little water into a saucer. Put it in the sun. Check it every hour. What happens?

Evaporation in the kitchen

You can watch evaporation happen fast in the kitchen.

When a kettle or pot boils, you see white "steam" coming out. That is water vapour turning back into tiny drops as it hits cooler air. The water in the pot is becoming gas and leaving.

If you boil a pot of water for a long time, the pot can go dry. All the water has evaporated into the air.

Heat makes evaporation faster. That is why:

• Clothes dry quickly on a hot, sunny day.
• Clothes dry slowly on a cool, cloudy day.
• A puddle dries fast at midday but slowly in the evening.

Try this: Ask an adult to boil water. Watch the "steam". Hold a cold metal spoon near it (not in it). What appears on the spoon?

Plants give off water too

It is not only seas and rivers that put water into the air. Plants do it as well.

Plants take in water through their roots. The water travels up the stem to the leaves. Then tiny holes in the leaves let water vapour escape into the air. This is called transpiration.

A big tree can put hundreds of litres of water into the air in one day. A forest puts out so much that it helps make its own clouds and rain.

That is one reason forests like Kakum have so much rain, and why cutting down too many trees can make a place drier.

Try this: Tie a clear plastic bag around a leafy branch in the sun. Leave it for a few hours. Look inside the bag. What do you see?

Stage 2: Condensation

Condensation is when water vapour cools down and turns back into liquid drops.

As vapour rises, it goes higher and higher, where the air is cold. Cold air cannot hold much vapour. So the vapour turns into tiny drops of water, far too small to fall.

Millions and millions of these tiny drops floating together make a cloud.

So a cloud is not smoke or cotton wool. A cloud is water, in very small drops, floating in the sky.

Condensation is the opposite of evaporation:

• Evaporation: liquid → gas (needs heat)
• Condensation: gas → liquid (needs cooling)

Try this: Breathe out on a cold mirror or window. What appears? That is the vapour in your breath condensing.

Condensation you can see

You see condensation every day without knowing it.

A cold bottle of water. Take a bottle out of the fridge. In a few minutes the outside is wet. That water did not leak out. Vapour in the warm air touched the cold bottle, cooled, and turned into drops.

Dew. Early in the morning, grass and leaves are wet, even if it did not rain. At night the ground gets cold. Vapour in the air condenses on the cold leaves. This is dew.

A steamy bathroom. After a hot bath, the mirror is misty. The warm vapour condensed on the cooler mirror.

Try this: Go outside early tomorrow. Touch the grass. Is it wet? Was there rain in the night?

Clouds

Clouds come in different shapes, and each shape tells a story.

White, fluffy clouds on a sunny day are made of small drops. They usually mean fair weather.

Flat, grey clouds that cover the whole sky often bring light, steady rain.

Tall, dark, towering clouds are the ones to watch. They can be many kilometres high. Inside, warm air rushes up and drops crash into each other. These clouds bring heavy rain, thunder and lightning. In Ghana we see them a lot in the rainy season.

When the sky suddenly goes dark in the afternoon and the wind picks up, a tall storm cloud is coming.

Try this: Look at the sky at the same time for five days. Draw the clouds. Did it rain on the days with tall, dark clouds?

Stage 3: Precipitation

Precipitation is water falling from clouds to the ground.

Inside a cloud, the tiny drops bump into each other and join up. They get bigger and bigger. When a drop is too heavy for the air to hold, it falls.

In Ghana, precipitation almost always means rain.

In very cold countries, the drops freeze on the way down. Then precipitation can be snow (soft ice flakes) or sleet (half-frozen rain).

Sometimes, even in Ghana, a strong storm throws drops up and down inside a cloud until they freeze into balls of ice. These fall as hail. It is rare, but it happens.

Try this: How many kinds of precipitation can you name? Which have you seen with your own eyes?

Rain in Ghana

Ghana has two main seasons: the rainy season and the dry season.

In the south (Accra, Kumasi, Cape Coast, Takoradi), there are two rainy seasons. The big rains come from about April to July. The small rains come around September to November.

In the north (Tamale, Bolgatanga, Wa), there is one rainy season, from about May to October. Then it is dry for the rest of the year.

The wettest part of Ghana is the south-west, near Axim. The driest part is the far north-east and the coast around Accra.

Try this: Which part of Ghana do you live in? When does the rain usually start where you are?

The Harmattan

From about December to February, a dry, dusty wind blows into Ghana from the Sahara Desert in the north. We call it the Harmattan.

During Harmattan:

• The air is very dry. Lips crack and skin feels dry.
• The sky looks hazy and white with dust.
• Mornings are cool, afternoons are hot.
• There is almost no rain.

Why no rain? The Harmattan air comes from the desert, so it carries very little water vapour. No vapour means no clouds, and no clouds means no rain.

The north of Ghana feels the Harmattan most strongly. Accra feels it a little.

Try this: Ask an older person how they know the Harmattan has arrived. What signs do they look for?

Stage 4: Collection

Collection is where the rain ends up after it falls.

Some rain falls straight into the sea, lakes and rivers.

Some falls on the land and runs downhill into streams. The streams join rivers. The rivers flow to lakes or to the sea. This running water is called run-off.

Some rain soaks into the ground. It goes down through the soil and rock and is stored underground. This is groundwater. Wells and boreholes pump it back up for us to drink.

Some rain lands on leaves and roofs and evaporates straight back up.

All the collected water waits for the sun to warm it, and the cycle begins again.

Try this: After the next rain, follow the water on your compound. Where does it run to?

Rivers and lakes in Ghana

Ghana's biggest river is the Volta. It collects rain from a huge area, even from other countries like Burkina Faso.

Lake Volta is one of the largest man-made lakes in the world. It was made when the Akosombo Dam was built across the Volta River in the 1960s.

Other important rivers are the Pra, the Ankobra, the Tano, the Densu (which fills the Weija reservoir for Accra's water) and the White Volta and Black Volta in the north.

All of these rivers are part of the water cycle. The rain that falls in Kumasi today may flow down the Pra and reach the sea at Shama in a few weeks.

Try this: Which river is nearest to your school? Where does it start and where does it end?

Groundwater, wells and boreholes

Not all rain runs away. A lot of it sinks into the ground.

Soil and some rocks have tiny spaces in them, like a sponge. Water fills these spaces. Deep down, there can be huge amounts of water stored in the rock. This is groundwater.

When people dig a well or drill a borehole, they are reaching down to this stored water. Many villages and schools in Ghana get their drinking water this way.

Groundwater is usually cleaner than river water, because the soil filters it. But if the rain stops for a long time, the groundwater level goes down and wells can run dry.

Try this: Pour water slowly onto a flowerpot of dry soil. Does it sit on top, or soak in? Where does it go?

The sea: the biggest store of water

Most of the water on Earth, about 97 out of every 100 buckets, is in the sea. Ghana's coast touches the Gulf of Guinea, part of the Atlantic Ocean.

Sea water is salty. We cannot drink it.

But here is something clever. When sea water evaporates, only the water rises. The salt stays behind in the sea. So the clouds, and the rain that falls from them, are fresh, not salty.

That means the sea is where most of our rain comes from. Ghana's rainy season begins when winds blow moist air in from the Gulf of Guinea.

Try this: Dissolve a spoon of salt in a little water in a saucer. Leave it in the sun until the water is gone. What is left?

The sun is the engine

Every stage of the water cycle needs energy, and that energy comes from the sun.

• The sun heats the sea and lakes so water evaporates.
• The sun warms the air so it rises and carries vapour up high.
• The sun warms the land, creating winds that blow clouds from the sea over the land.

Without the sun, there would be no evaporation, no clouds, no rain. The water would just sit still.

At night, when there is no sun, evaporation slows down and condensation (dew) happens instead. That is why mornings are damp and afternoons are dry.

Try this: Put two wet cloths outside, one in the sun and one in the shade. Which dries first? Why?

Why the water cycle matters: drinking water

Every person needs clean water to drink, cook and wash. All of it comes from the water cycle.

• Rain fills rivers and reservoirs like Weija and Kpong. Ghana Water Company cleans this water and sends it through pipes to homes.
• Rain soaks into the ground and fills the boreholes and wells that villages use.
• Rain fills the tanks people put under their roofs.

If the rains fail, reservoirs drop, taps run dry and people must walk far to find water.

So when you hear adults worrying about late rains, they are worrying about the water cycle.

Try this: Where does the water in your home come from? Pipe, borehole, well, tank or sachet? Find out.

Why it matters: farming

Most farmers in Ghana depend on rain to grow food. We call this rain-fed farming.

Maize, yam, cassava, rice, cocoa, plantain and vegetables all need water at the right time.

• Farmers plant when the rains begin.
• If the rains come late, planting is late and the harvest is smaller.
• If the rains stop too early, crops dry up before they are ready.
• If there is too much rain, fields flood and crops rot.

Cocoa, Ghana's famous crop, needs lots of rain spread through the year. That is why cocoa grows in the wetter south and not in the dry north.

Try this: Ask a farmer or a market seller which months are best for their crop and why.

Why it matters: electricity

The water cycle even gives us electricity.

Rain fills Lake Volta. The water flows through the Akosombo Dam. As it rushes through, it spins huge machines called turbines, and they make electricity. This is called hydroelectric power. The Bui Dam on the Black Volta and the Kpong Dam do the same.

When the rains are good, the lake is full and the dams make plenty of power.

When the rains are poor for a few years, the lake level drops. The dams make less power, and the country can have power cuts, which Ghanaians call "dumsor".

Try this: Next time the lights go off, think about where the electricity comes from and what the water cycle has to do with it.

Too much water: floods

Sometimes the water cycle brings too much rain at once.

When heavy rain falls faster than the ground can soak it up, water runs over the land and into streets and houses. This is a flood.

Accra floods almost every June. Why?

• Very heavy rain in a short time.
• Gutters and drains blocked with plastic rubbish.
• Houses built on places where water used to flow.
• Concrete everywhere, so water cannot soak into the ground.

Floods destroy homes, spread disease and can take lives. Keeping gutters clear and not throwing rubbish in drains helps the water go where it should.

Try this: Look at the gutter nearest your school. Is it clear or blocked? What would happen in heavy rain?

Too little water: drought

Sometimes the rains do not come, or come much less than usual. This is a drought.

In a drought:

• Rivers and dams get low.
• Wells dry up.
• Crops wither and animals have nothing to drink.
• Food becomes scarce and expensive.

Northern Ghana is more at risk of drought because it has only one rainy season. If that season fails, it is a long wait until the next one.

People prepare by storing water in tanks and dams, digging deeper boreholes, and planting crops that need less water.

Try this: How could your school store rainwater from the roof for use in the dry season?

Dirty water and the cycle

The water cycle moves water, but it also moves whatever is in the water.

If rubbish, chemicals or sewage are thrown into a stream, they flow into rivers and the sea, and into the fish we eat.

Illegal mining, called galamsey, uses chemicals and churns up mud. Rivers like the Pra and Ankobra have turned brown and poisonous in places. Water companies struggle to clean water from these rivers.

Rain that falls through smoky, dusty air also picks up dirt.

The cycle is clean only if we keep the water clean. Water that evaporates leaves the dirt behind, but the dirt stays in the river for the people and animals who live there.

Try this: List three things people should never put in a stream or gutter.

Experiment: make a mini water cycle

You can make the whole water cycle in a bowl.

You need: a large bowl, a small cup, clear plastic wrap, a small stone, water, a sunny spot.

1. Pour water into the bowl until it is about two fingers deep. This is the "sea".
2. Stand the empty cup in the middle. Its top must be above the water.
3. Cover the bowl tightly with plastic wrap.
4. Put the small stone on the wrap, right above the cup, so the wrap dips down in the middle.
5. Put the bowl in the sun for a few hours.

What happens: The sun warms the "sea". Water evaporates, condenses on the cool wrap, runs down to the dip, and drips into the cup as "rain".

Try this: Taste the water in the cup (if the bowl was clean). Is it salty if you put salt in the "sea"?

Experiment: the disappearing puddle

You need: chalk, a puddle or a bowl of water on the ground, a sunny day.

1. Find a puddle after rain, or pour water on a flat concrete spot.
2. Draw a chalk line around the edge of the water.
3. Come back every 30 minutes and draw a new line.
4. Watch the lines get closer to the middle.

What is happening: The sun is turning the liquid water into vapour. The water is not leaking away through the concrete; it is rising into the air.

Think: Would it disappear faster or slower on a cloudy day? At night? In Harmattan, when the air is very dry?

Try this: Do it twice, once in sun and once in shade. Compare how long each takes.

Experiment: the cold bottle

You need: a bottle of water from the fridge, a dry cloth, a warm day.

1. Dry the outside of the cold bottle completely.
2. Put it on a table in the open air.
3. Wait five minutes.

What happens: The outside becomes wet with tiny drops.

Why: The air around you is full of invisible water vapour. When it touches the cold bottle, it cools and condenses into liquid drops. This is exactly how clouds form, except in the sky, the "cold bottle" is the cold air high up.

Try this: Try the same thing with a bottle that is not cold. Does it get wet? Why not?

Reading a weather forecast

The Ghana Meteorological Agency (GMet) studies the water cycle every day and tells us what to expect. You can hear forecasts on the radio and TV.

Words you will hear:

• Cloudy: lots of condensation up high; rain may come.
• Scattered showers: rain in some places but not everywhere.
• Thunderstorm: tall storm clouds with lightning and heavy rain.
• Humid: lots of water vapour in the air; it feels sticky.
• Dry and hazy: Harmattan; little vapour, lots of dust.

Farmers, fishermen, pilots and even football coaches use the forecast to plan their day.

Try this: Listen to today's forecast. Write down the words that describe the water cycle.

The water cycle and the seasons

Why does Ghana have a rainy season and a dry season at all?

It is about where the moist air comes from.

In the rainy season, winds blow from the south-west, over the Gulf of Guinea. This air is warm and full of vapour from the sea. When it reaches the land and rises, it cools, condenses and rains.

In the dry season, winds blow from the north-east, over the Sahara. This air is dry. There is little vapour, so there are few clouds and little rain. This is the Harmattan.

The line where the two winds meet moves north and south through the year, and the rain moves with it.

Try this: Hold a wet finger up in the wind. Which side feels cold? That is where the wind is coming from.

Water never disappears

Here is the amazing thing about the water cycle. The amount of water on Earth stays the same.

Water is not made and it is not destroyed. It just moves and changes form.

The water you drank this morning might have:

• fallen as rain on Kumasi last month,
• been part of the Pra River,
• evaporated from the sea near Takoradi,
• floated as a cloud over Cape Coast,
• been drunk by a dinosaur millions of years ago!

This is why we must look after water. We cannot make more. We can only keep what we have clean and use it wisely.

Try this: Write a short story about one drop of water and its journey around the cycle.

Saving water at home and school

Because the water cycle gives us only so much clean water, we should not waste it.

• Turn the tap off while brushing your teeth.
• Fix dripping taps. One drip per second wastes thousands of litres a year.
• Use a bucket to wash the car, not a running hose.
• Catch rainwater from the roof in a tank for washing and watering plants.
• Water plants in the evening so the water soaks in instead of evaporating.
• Do not leave the shower running.

Every litre saved is a litre that stays in the reservoir for the dry season.

Try this: Count how many times you use water today. Pick one way to use less tomorrow.

The water cycle and living things

Every living thing needs water, so every living thing depends on the water cycle.

• Plants take in rain through their roots and give out vapour through their leaves.
• Animals drink from rivers and ponds that rain filled.
• Fish live in the rivers and lakes of the cycle.
• People drink, cook, wash and farm with water from the cycle.

Your body is more than half water. You lose water when you sweat, breathe out and go to the toilet. You put it back when you drink. You are part of the water cycle too!

Try this: Breathe onto the back of your hand. Does it feel damp? That is water vapour leaving your body.

Words to remember

• Water cycle: the never-ending journey of water from the ground to the sky and back.
• Evaporation: liquid water turning into vapour and rising. Needs heat.
• Water vapour: water as an invisible gas.
• Condensation: vapour cooling and turning back into liquid drops. Makes clouds and dew.
• Precipitation: water falling from clouds: rain, hail, snow.
• Collection: rain gathering in rivers, lakes, the sea and underground.
• Groundwater: water stored in the ground; wells and boreholes reach it.
• Run-off: rain that flows over the land into streams.
• Transpiration: plants giving off water vapour from their leaves.
• Harmattan: the dry, dusty wind from the Sahara.

Try this: Cover the meanings and test a friend.

Practice: the four stages

1. Name the four stages of the water cycle in order.
2. Which stage needs heat from the sun?
3. Which stage makes clouds?
4. Which stage fills rivers and lakes?
5. What is water vapour? Can you see it?
6. Why do wet clothes dry faster on a sunny day?
7. What is dew, and when does it form?
8. Why is rain not salty, even though most of it comes from the sea?
9. What does "precipitation" mean? Give two examples.
10. Where does groundwater come from?

Write your answers in full sentences. Then swap with a friend and compare.

Practice: Ghana and the cycle

1. Which months are the big rainy season in southern Ghana?
2. How many rainy seasons does northern Ghana have?
3. What is the Harmattan and where does it come from?
4. Name two rivers in Ghana.
5. How was Lake Volta made?
6. How does the Akosombo Dam use the water cycle?
7. Give two reasons why Accra floods.
8. Why is drought a bigger danger in the north than in the south?
9. How does galamsey harm the water cycle?
10. Give three ways to save water at home.

Choose one question and explain your answer to someone at home tonight.

Draw the cycle

Draw your own water cycle picture. Include:

• The sun in the corner.
• The sea or a lake at the bottom.
• Arrows going up for evaporation. Label them.
• A cloud at the top. Label "condensation".
• Rain falling from the cloud. Label "precipitation".
• A river running back to the sea. Label "collection".
• A tree with a small arrow from its leaves for transpiration.
• A well showing groundwater.

Add something from Ghana: a dam, a cocoa farm, a fishing boat, your own town.

Colour it and explain it to your class in one minute.

Check yourself

Tick the ones you can do.

• I can name the four stages of the water cycle in order.
• I can explain evaporation and give an example from home.
• I can explain condensation and give an example from home.
• I know that clouds are made of tiny water drops.
• I know what precipitation is.
• I can explain where rain goes after it falls.
• I know when the rainy season is where I live.
• I can explain what the Harmattan is.
• I can give two reasons the water cycle matters for Ghana.
• I can do one experiment to show evaporation or condensation.

Go back to any page you need. Try the experiments more than once; scientists always repeat their tests.

Learn more

• BBC Bitesize: What is the water cycle? — a short illustrated guide with a quiz
• NASA Climate Kids: What is the water cycle? — the cycle explained with pictures from space
• USGS Water Science School: The water cycle — diagrams and detail for pupils who want to go deeper
• Ghana Meteorological Agency — today's forecast and the rainy-season outlook for Ghana

Watch more

Think about it

1. If the sun stopped shining for a month, what would happen to the water cycle?
2. Why do you think the north of Ghana is drier than the south?
3. The water you drink today may have been rain over Kumasi last month. How does that make you feel about keeping rivers clean?
4. What would happen to Accra's floods if everyone stopped throwing plastic in the gutters?
5. How could your school catch and store rainwater for the dry season?