💧 The Water Cycle
In one sentence: Water moves between the ocean, air, land, and living things — changing form but never disappearing.
Interactive tool
Use this interactive learning tool in study mode.
🔑 The key exam point
Global scale
- CLOSED system
- No water enters or leaves Earth
- Same water recycled forever
Local scale
- OPEN system
- Water flows in and out
- Rivers bring water in, evaporation takes it out
Earth has had the same water for billions of years — you might be drinking water a dinosaur peed in! 🦕
📦 Where water is stored
Think of these as water tanks around the planet:
- 🌊 Oceans — the BIG one (97% of all water, but salty!)
- 🧊 Ice & glaciers — frozen freshwater at poles and mountains
- 🕳️ Groundwater — underground in rocks and soil (aquifers)
- 🏞️ Rivers & lakes — surface freshwater we can see
- ☁️ Atmosphere — tiny amount, but moves a LOT of water
- 🌱 Living things — water inside plants and animals
🔄 How water moves (the flows)
Water moves between stores through these processes:
- ☀️ Evaporation — sun heats water → turns to vapour (liquid → gas)
- 🌿 Transpiration — plants release water through their leaves
- ☁️ Condensation — vapour cools → forms clouds (gas → liquid)
- 🌧️ Precipitation — water falls as rain, snow, hail
- ⬇️ Infiltration — water soaks into soil
- ⬇️⬇️ Percolation — water sinks deeper into groundwater
- 🏃 Runoff — water flows over land into rivers/sea
Memory trick: Evapotranspiration = evaporation + transpiration combined. Examiners love this word!
🏗️ How humans mess with the water cycle
- 🏙️ Cities & roads — concrete stops infiltration → more flooding
- 🪓 Deforestation — fewer trees = less transpiration + more runoff
- 🚿 Taking too much water — lowers rivers and groundwater
- 🌡️ Climate change — changes when and where rain falls
Humans change both where water is stored and how fast it moves.
📝 What examiners actually ask
- Name the stores and flows in the water cycle
- Explain why it's closed globally but open locally
- Describe how deforestation or urbanisation affects the cycle
- Draw and label a simple diagram
Exam Tips:
- Always use proper terms: say 'precipitation' not just 'rain'
- If asked about stores and flows — name BOTH and explain the connection
- Link human impacts to SPECIFIC processes (e.g., 'concrete reduces infiltration')
- Remember: closed system globally, open system locally — this is a favourite trick question!
Free preview
This is the free notes preview
You're reading the free notes. Aimnova Pro unlocks the full study experience — and you can try it free for 7 days:
- FlashcardsLock in vocabulary and key terms with spaced repetition.
- Practice questionsAnswer exam-style questions and get instant AI marking.
- Mock exams & past-paper vaultSit full mocks and see exactly how examiners award marks.
- Personalised study planA daily plan built around your exam date and weak areas.
IB-style question — Outline transfers in the water (hydrological) cycle
Outline the main transfers and stores of water in the hydrological cycle. [4]
How to answer it, step by step
- Into the atmosphere
• Evaporation: solar energy converts liquid water to vapour (oceans, lakes, soil).
• Transpiration: plants release vapour through stomata. Condensation forms clouds. - Return to land/ocean + key stores
• Precipitation (rain, snow) → surface runoff → rivers → ocean; or infiltration → groundwater.
• Largest store: oceans; smallest: atmosphere.
Final answer
Name the processes (evaporation, transpiration, condensation, precipitation, runoff, infiltration) — vague phrases like 'water goes up and comes back down' score nothing. Four distinct named points = 4 marks.
IB-style question — Deforestation positive feedback on the water cycle
Describe the positive feedback process by which deforestation can reduce regional water availability. [2]
How to answer it, step by step
- First causal step
• Fewer trees → less evapotranspiration → less water vapour → reduced cloud formation and precipitation. - Feedback loop closes
• Less rainfall → soil dries → remaining vegetation stressed → further tree loss → even less rain.
• This is positive feedback: the effect reinforces the original cause.
Final answer
Two marks require a complete loop, not just one step. Examiners look for the circular chain where less forest causes less rain which causes even less forest. One causal link alone scores only 1.