Exercise Solutions Available
Step-by-step answers for all textbook questions in this chapter
Importance of Water
Water is essential for all life:
- All living organisms (animals, plants, humans) need water to survive.
- Water is used for drinking, cooking, bathing, irrigation, and industry.
- About 71% of Earth's surface is covered with water — but most is salty (oceans). Only 3% is fresh water, and most of that is locked in glaciers.
Sources of Water
| Source | Type |
|---|---|
| Rain | Main source of all fresh water |
| Rivers and streams | Surface water |
| Lakes and ponds | Surface water |
| Wells | Groundwater |
| Springs | Groundwater coming to surface |
| Glaciers | Frozen water; melts to form rivers |
The Water Cycle
Water constantly moves between the Earth's surface and the atmosphere in a cycle:
Step 1 — Evaporation:
- Sun heats water in oceans, rivers, lakes → water evaporates (becomes water vapour).
- Plants also release water vapour through leaves (transpiration).
Step 2 — Condensation:
- Water vapour rises, cools at higher altitude → condenses into tiny water droplets.
- These droplets form clouds.
Step 3 — Precipitation:
- Water falls from clouds as rain, snow, hail, or sleet.
Step 4 — Collection:
- Water collects in rivers, lakes, oceans.
- Some seeps into the ground (infiltration) → becomes groundwater.
- Cycle repeats.
This is called the hydrological cycle or water cycle.
Groundwater
- Rain soaks into the soil through a process called infiltration.
- The water fills spaces in soil and rocks, forming the water table.
- Wells tap into groundwater.
- Springs form where the water table meets the surface on a hillside.
Factors affecting groundwater level
- More trees → more infiltration → higher water table.
- Concrete paving → less infiltration → lower water table.
- Excessive extraction → water table drops.
Water Shortage and Drought
- A drought is a prolonged period without rain — leads to water shortage.
- Effects: crop failure, food shortage, people and animals die.
- Areas affected: Rajasthan, parts of Maharashtra, Vidarbha.
Water Conservation
Ways to save water:
| At Home | In Agriculture | Community Level |
|---|---|---|
| Fix leaking taps | Drip irrigation | Rainwater harvesting |
| Use bucket not shower | Grow drought-resistant crops | Check water pipelines |
| Reuse washing water | Water crops at dawn/dusk | Lakes and ponds |
| Turn off tap while brushing | Mulching to reduce evaporation | — |
Rainwater Harvesting
- Collecting and storing rainwater for later use.
- Can be done on rooftops — pipes lead to underground storage tanks.
- Rooftop water can be used for garden/toilets, or allowed to seep into ground.
Floods
- Excessive rainfall causes rivers to overflow → flooding.
- Destroys crops, houses, roads; causes loss of life.
- More trees in a catchment area → roots hold soil → less runoff → reduces flood risk.
Key Vocabulary
| Term | Meaning |
|---|---|
| Evaporation | Water changing to vapour |
| Condensation | Vapour changing to liquid droplets |
| Precipitation | Rain, snow, hail falling from clouds |
| Infiltration | Water seeping into the ground |
| Groundwater | Water stored below the ground |
| Water table | Upper level of groundwater |
| Drought | Long period without rain |
| Rainwater harvesting | Collecting rainwater for use |
| Water cycle | Continuous movement of water between land and atmosphere |
Exam Tips
- Draw and label the water cycle — evaporation, condensation, precipitation, collection — a very common diagram question.
- Groundwater = rainwater that seeps into soil — wells tap groundwater.
- Drought = no rain for long time; flood = too much rain — opposite extremes.
- List 4–5 water conservation methods for 3-mark questions.
- Rainwater harvesting definition and one method — common short answer.
Frequently Asked Questions
The water cycle is the continuous movement of water between Earth's surface and the atmosphere. Water evaporates from oceans, rivers, and lakes → forms clouds → falls as rain or snow (precipitation) → collects in rivers and oceans again.