A river's journey: source, tributaries and delta
A tiny stream trickles from a hill rock near a village. By the time it reaches the town it is a wide river. How does a small stream grow so big?
A river begins at its source high in the hills. Smaller streams called tributaries join it, so it grows wider and stronger. Near the sea it spreads into many channels forming a delta. A river that flows all year is perennial; one that flows only after rain is seasonal.
In the figure: A river grows from left to right: source, tributaries joining, a wide river and finally a delta.
A river's journey: source, tributaries and delta
In the app you can move this figure with your finger.
Open in the appKey point 1: Parts of a river
- Easy : The place where a river starts is its source.
- Medium : Small streams that join a river are its tributaries.
- Exam-type : Where a river meets the sea and splits into many channels, a delta forms.
Key point 2: Godavari at a glance
- Easy : It starts at Trimbakeshwar in the Western Ghats of Maharashtra.
- Medium : It flows about 1,465 km to the Bay of Bengal and is the second longest river in India.
- Exam-type : It is perennial and is called Dakshina Ganga because it flows in the south and is considered sacred.
A tributary flows INTO a bigger river; it does not take water out of it.
Thinking that a river begins in the sea and flows up to the hills.
Source → Tributaries → Delta = Start, Add, End. Memory clue: "S-T-D: Start, Tributary, Delta".
Spot the difference
| Point | Perennial river | Seasonal river |
|---|---|---|
| Flows | all year | only after rain |
| Water source | rain, springs, snow | mainly rain |
| Example | Godavari | a rain-fed stream |
Practice questions
- 1What is the source of a river?
- 2What do we call a small river that joins a big river?
- 3Where does the Godavari begin?
- 4Which sea does the Godavari join?
- 5What is a delta?
- 6Is a river that dries up in summer perennial or seasonal?
- 7Why does a river become wider as it flows on?
- 8Why is the Godavari called Dakshina Ganga?
Show answers (try them yourself first)
- 1The place where it starts, usually high in hills.
- 2A tributary.
- 3At Trimbakeshwar in the Western Ghats (Maharashtra).
- 4The Bay of Bengal.
- 5Fan-shaped land where a river splits into channels near the sea.
- 6Seasonal.
- 7Rain and tributaries keep adding water.
- 8It flows in southern India and is regarded as sacred like the Ganga.
How rivers support people and nature
Why do old towns lie beside rivers? Because water for drinking, farming and trade is close by.
Rivers give water for drinking, cooking, washing, farming and factories. They give people livelihoods such as farming, fishing and boating. Rivers also hold forests, fish, turtles and birds. Visiting such places without harming them is ecotourism. At the delta, fresh river water meets salt sea water and mangrove forests grow.
In the figure: One river feeds both people and wildlife.
Key point 1: Rivers and people
- Easy : Homes and schools get river water through pipes.
- Medium : Canals carry river water to fields so farmers can grow crops.
- Exam-type : Fishing, boating, small industries and tourism give work to people near the river.
Key point 2: Rivers and nature
- Easy : Fish and turtles live in the water.
- Medium : Tigers, deer and many birds live in forests along the river.
- Exam-type : Mangrove forests at the delta shelter fish, crabs and birds.
Water used for growing crops is also taken from rivers, not only for drinking.
Thinking a river is useful only for drinking water.
River gives: Drink, Grow, Earn, Shelter. Memory clue: "D-G-E-S".
Spot the difference
| Use | Example | Who benefits |
|---|---|---|
| Drinking | tap water | families |
| Irrigation | canal to the farm | farmers |
| Livelihood | fishing, boats | fishers, boatmen |
Practice questions
- 1Name two uses of river water at home.
- 2How does river water reach farms?
- 3Name one job that depends on a river.
- 4Where do mangroves grow?
- 5Name two animals that live near the Godavari.
- 6What is ecotourism?
- 7Why did old settlements grow near rivers?
- 8Suggest one way to enjoy a river without harming it.
Show answers (try them yourself first)
- 1Drinking, cooking, washing (any two).
- 2Through canals and pipes.
- 3Fishing, boating, farming (any one).
- 4At river deltas where river water meets the sea.
- 5Tiger, barking deer, turtle, fish (any two).
- 6Visiting nature without harming it.
- 7Water for drink, food and travel was close by.
- 8Watch birds quietly and take away all litter.
Dams and river pollution
A tap works all summer because a dam stored rainwater months ago. But the same dam changed the river's flow and the lives of people upstream.
A dam is a wall across a river that stores water in a reservoir. Stored water gives drinking water, irrigation and electricity in dry months. But dams flood land and force people and animals to move. Pollution — plastic, waste, soapy water and fertilisers — harms rivers too.
In the figure: A dam turns a river's rain water into a store used later for water and electricity.
Key point 1: Good and bad of dams
- Easy : Dams store water for dry months.
- Medium : They also make electricity and help control floods.
- Exam-type : But reservoirs drown land, forests and homes, so people must move and animals lose habitat.
Key point 2: Pollution in rivers
- Easy : Plastic and household waste choke the river and harm fish and birds.
- Medium : Oil does not dissolve in water; sugar does. Some harmful things stay hidden even in clear-looking water.
- Exam-type : Fertilisers make plants grow so fast that they cover the surface like a green blanket and fish cannot breathe.
Clear-looking water can still be polluted.
Thinking a dam has only benefits and no problems.
Dam = store + power, but also shift + flood. Memory clue: "Store, Shine (power), Shift (people)".
Spot the difference
| Point | Benefit of dam | Problem of dam |
|---|---|---|
| Water | stored for dry months | river below gets less |
| Power | makes electricity | — |
| Land and people | — | land floods, people shift |
Practice questions
- 1What is a reservoir?
- 2Name two benefits of a dam.
- 3Name one problem caused by a dam.
- 4Does oil dissolve in water?
- 5Name two things that pollute a river.
- 6What is the "green blanket" on a river?
- 7Why should we not throw plastic into a pond?
- 8How can fertilisers harm a river?
Show answers (try them yourself first)
- 1A large store of water behind a dam.
- 2Stores water, makes electricity, helps irrigation (any two).
- 3People and animals lose land and homes.
- 4No. It floats on top.
- 5Plastic, waste, soapy water, fertilisers (any two).
- 6A thick cover of plants that grow too fast.
- 7It harms animals and does not rot away.
- 8They make plants grow too fast and block life in the water.
Floods, water shortage and saving water
In one city streets turn into rivers after a downpour; in another, families queue for tankers in summer. Both show water out of balance.
Too much rain makes a river overflow — a flood. Trees slow down rain and let soil soak it in, so cutting trees can cause flooding. Too little water — a drought or shortage — forces people to leave their homes. Saving water in small daily ways helps everyone.
In the figure: Both too much and too little water cause trouble for people and animals.
Key point 1: Staying safe in a flood
- Easy : Before: keep an emergency bag with food, medicines and a torch.
- Medium : During: listen to local news, go to higher ground and keep away from flood water and power lines.
- Exam-type : After: do not return until it is declared safe; clean and disinfect things.
Key point 2: Saving water
- Easy : Close the tap while brushing your teeth.
- Medium : Fix a leaking tap with an adult's help.
- Exam-type : Reuse clean water from washing fruit to water plants; remind family to save water.
Never walk, swim or drive through flood water.
Believing that one tap left dripping does not matter.
Flood: Prepare, Move up, Wait for safe. Saving: Close, Fix, Reuse. Memory clue: "P-M-W" and "C-F-R".
Spot the difference
| Point | Flood | Water shortage |
|---|---|---|
| Cause | too much rain, no trees | too little rain, waste |
| Effect | homes and crops damaged | dry wells, people move |
| Remedy | trees, safe shelter | save and reuse water |
Practice questions
- 1What is a flood?
- 2Name one thing to keep in an emergency bag.
- 3Why are trees useful in heavy rain?
- 4What should you avoid touching in a flood?
- 5Why do families leave their homes in a long drought?
- 6Name two ways to save water at home.
- 7What can we do with clean water left after washing vegetables?
- 8Why can a dripping tap be a big problem?
Show answers (try them yourself first)
- 1A river overflowing its banks and covering land.
- 2Food, medicines, torch (any one).
- 3They slow the rain and help soil soak it in.
- 4Flood water and power lines.
- 5Because there is no water to drink or farm.
- 6Close the tap, fix leaks, reuse water (any two).
- 7Use it to water plants.
- 8Drips add up to many litres wasted.