Learning Objectives
- Understand the importance of water
- Learn about water distribution on Earth
- Know about water cycle and groundwater
- Understand water conservation methods
Key Concepts
Water Distribution
About 71% of Earth's surface is covered with water. But only about 3% is freshwater, and most of that is locked in ice caps and glaciers. Less than 1% is available as usable freshwater.
Forms of Water
- Solid: Ice, snow, glaciers
- Liquid: Rivers, lakes, groundwater, oceans
- Gas: Water vapour in atmosphere
Water Cycle
The continuous circulation of water in nature:
Evaporation (water → vapour by sun's heat) → Condensation (vapour → clouds) → Precipitation (rain, snow, hail) → water flows into rivers, lakes, or seeps underground → cycle repeats.
Transpiration from plants also adds water vapour to the atmosphere.
Groundwater
Water table: The upper level of underground water. It varies from place to place and season to season.
Aquifer: Underground layer of rock/soil that holds groundwater.
Depletion of water table: Caused by increasing population, industrial use, agricultural overuse, deforestation, and scanty rainfall.
Water Management and Conservation
- Rainwater harvesting: Collecting and storing rainwater for later use
- Drip irrigation: Water supplied directly to plant roots, reducing wastage
- Bawris (stepwells): Traditional water harvesting structures in Rajasthan
- Fix leaking taps and pipes
- Reuse water where possible
- Do not waste water during daily activities
Summary
Only a small fraction of Earth's water is usable freshwater. The water cycle circulates water continuously. Groundwater levels are depleting due to overuse. Water conservation through rainwater harvesting, efficient irrigation, and reducing wastage is essential for survival.
Important Terms
- Water table: Upper level of underground water
- Aquifer: Underground water-bearing rock layer
- Water cycle: Continuous circulation of water in nature
- Rainwater harvesting: Collecting rainwater for use
- Drip irrigation: Efficient water delivery to plant roots
Quick Revision
- 97% saltwater, 3% freshwater, less than 1% usable
- Water cycle: Evaporation → Condensation → Precipitation
- Groundwater depletion: overuse, deforestation, less rainfall
- Conservation: rainwater harvesting, drip irrigation, fix leaks
- June 22 = World Rainwater Harvesting Day concept