Learning Objectives
- Understand the importance of water for life
- Learn about the water cycle and its stages
- Know about different sources of water
- Understand conservation of water and its need
Key Concepts
Importance of Water
Water is essential for all living beings. We need water for drinking, cooking, bathing, washing, farming, and industrial use. Plants need water to make food through photosynthesis. Animals need water to survive. About 71% of the Earth's surface is covered with water, but only a small fraction (less than 3%) is fresh water that we can use.
Sources of Water
Water comes from many sources. Rain is the main source of water on Earth. Surface water includes rivers, lakes, ponds, and streams. Groundwater is found underground, accessed through wells, tube wells, and hand pumps. Seawater in oceans and seas is salty and cannot be used for drinking directly.
The Water Cycle
The water cycle is the continuous movement of water between the Earth's surface and the atmosphere. It has these stages:
- Evaporation: Heat from the Sun causes water from rivers, lakes, and oceans to turn into water vapour. This vapour rises into the air.
- Condensation: As water vapour rises, it cools down and forms tiny water droplets. These droplets gather to form clouds.
- Precipitation: When clouds become heavy with water droplets, the water falls back to Earth as rain, snow, or hail.
- Collection: The rainwater flows into rivers, lakes, and oceans, or seeps underground. The cycle then repeats.
Conservation of Water
Fresh water is limited and precious. We must conserve water for future generations. Ways to conserve water include: turning off taps when not in use, fixing leaky taps and pipes, using a bucket instead of a hose for washing, collecting rainwater (rainwater harvesting), watering plants in the evening to reduce evaporation, and not polluting water bodies.
Drought and Floods
When there is very little or no rain for a long time, a drought occurs. Crops fail, water sources dry up, and there is a severe shortage of water. When it rains too heavily, rivers overflow and cause floods, damaging homes, crops, and property.
Summary
Water is vital for all life on Earth. It is available from rain, rivers, lakes, and underground sources. The water cycle continuously circulates water through evaporation, condensation, precipitation, and collection. Since fresh water is limited, we must conserve it. Too little rain causes drought and too much rain causes floods.
Important Terms
- Water Cycle: The continuous movement of water between Earth and atmosphere
- Evaporation: Water changing from liquid to vapour due to heat
- Condensation: Water vapour cooling and forming water droplets (clouds)
- Precipitation: Water falling from clouds as rain, snow, or hail
- Groundwater: Water found underground in soil and rocks
- Drought: A long period with very little or no rain
- Rainwater Harvesting: Collecting and storing rainwater for later use
Quick Revision
- About 71% of Earth is covered with water, but less than 3% is fresh water
- Water cycle: Evaporation โ Condensation โ Precipitation โ Collection
- Rain is the main source of water
- Groundwater is accessed through wells and tube wells
- Conservation: fix leaks, rainwater harvesting, use water wisely
- Too little rain โ drought; too much rain โ floods
- Water exists in three states: solid (ice), liquid (water), gas (water vapour)