1
💧 The Hydrosphere
The hydrosphere is ALL the water found on, under, and above Earth's surface — in every form.
| Form of water | Where it is found |
|---|
| Liquid | Oceans, rivers, lakes, groundwater, tiny drops in clouds |
| Solid (ice) | Glaciers, ice caps, snow — mostly in polar regions |
| Gas (vapour) | Atmosphere — when Sun's heat evaporates surface water |
Key facts:
🌍 75% of Earth's surface is covered by water → Earth is called the Blue Planet
🌊 97.5% of all water is saltwater (oceans)
💧 Only 2.5% is fresh water — and most of that is frozen in glaciers
🚰 Less than 1% is easily available for living things to use
Hydro = water. The hydrosphere includes ALL water on Earth — oceans, rivers, lakes, glaciers, groundwater AND water vapour in the air!
2
🔄 The Water Cycle
Water is always moving and changing form. The water cycle is continuous — it never stops!
| Stage | What happens |
|---|
| Evaporation | Sun heats water → turns into water vapour → rises into the air |
| Transpiration | Plants release water vapour through their leaves into the air |
| Condensation | Water vapour cools → turns back into liquid droplets → forms clouds |
| Precipitation | Cloud gets too heavy → releases water as rain, hail or snow |
| Runoff | Water flows over land into rivers, lakes and oceans |
| Infiltration | Water seeps into the ground → becomes groundwater |
| Sublimation | In very cold areas, ice/snow turns directly into vapour (no liquid stage) |
Sun heats water→
Evaporation→
Condensation (clouds)→
Precipitation (rain/snow)→
Runoff & Groundwater→
Back to oceans ↺
The water cycle PURIFIES water! Evaporation leaves impurities behind, so the water vapour that rises is cleaner than what was in the ocean.
3
🌍 Water & the Hydrosphere — Impact on Land & Vegetation
Water from the hydrosphere shapes the land and supports all life. But pollution threatens this balance.
- Rivers shape valleys and carry sediments — water carves the land over time
- Rain and runoff erode soil and carry nutrients that feed plants and ecosystems
- Vegetation depends on water from rivers, rain and groundwater to survive
- Floods can deposit nutrient-rich sediments → fertile land for farming
- Droughts (lack of water) cause vegetation to die and soil to dry out
⚠️ Threats to the hydrosphere:
Rubbish thrown into rivers and oceans → kills aquatic animals
Oils and chemicals poured into drains → travel to seas and rivers
Factory chemical waste dumped in water → extreme contamination
Oil spills from ships → catastrophic damage to marine life
✅ How to protect water:
Never throw rubbish into rivers or seas
Don't pour oils or paints down drains
Encourage good habits in your family and community
Looking after water = looking after life. Without clean water, there are no plants, no animals, no humans.
4
⚡ Hydropower — Water as Energy
Hydropower (or hydroelectric power) uses the energy of moving or falling water to generate electricity. It is a renewable energy source — it doesn't run out like fossil fuels.
How a hydropower plant works:
1A dam is built across a river, creating a large reservoir of water at a high point.
2Water flows down through large pipes (penstocks) from high to low elevation.
3Falling water pushes against the blades of a turbine, making it spin.
4The spinning turbine powers a generator that converts movement into electricity.
5Electricity is sent through power lines to homes, schools and businesses.
✅ Advantages
Renewable — water is never used up
No carbon dioxide or greenhouse gases
Clean — doesn't pollute air or water
Electricity can be cheaper to produce
Can handle peak demand easily (control the dam gates)
⚠️ Environmental impacts
Dam blocks fish migration routes
Reservoir floods large natural areas, farmland and homes
Changes water temperature and river flow
Kills native plants and animals in the river
Sediment builds up behind the dam → depletes oxygen downstream
Depends on rainfall — droughts reduce power production
The key balance: hydropower is CLEAN energy (no pollution, no greenhouse gases) but it can HARM ecosystems by changing rivers and flooding land. Both sides matter for the exam!