7.4 Water Cycle

Last updated at May 22, 2026 by

Image: A labelled water cycle diagram showing the Sun heating the ocean causing evaporation, water vapour rising and forming clouds, precipitation falling as rain and snow over mountains, rivers flowing back to the ocean, and an arrow showing infiltration of rainwater into the ground — the complete natural water cycle
    Note
    In Water cycle, all 3 methods of heat transfer are used
    Conduction, Convection and Radiation

    Explanation
  • Radiation: Heat from the Sun reaches Earth by radiation and warms oceans, rivers, lakes, and land. This heat helps water evaporate and start the water cycle.
  • Conduction: Warm land or water heats the air touching it by direct contact. This makes the nearby air warmer.
  • Convection: Warm, moist air becomes lighter and rises upward. As it rises, it cools and forms clouds.
Image: A labelled diagram of the water cycle showing the Sun causing evaporation from oceans and lakes, water vapour rising, condensing into clouds, precipitation falling as rain or snow, water flowing back into rivers, seeping into groundwater, and cycling again
☀️ Evaporation
Sun’s heat reaches Earth by R adiation and warms oceans, rivers, lakes, and land.
Water evaporates into vapour, and plants add water vapour through transpiration.
↓
☁️ Condensation
Warm land and water heat the air touching them by C onduction .
This warm, moist air becomes lighter and rises upward by C onvection .
As warm water vapour rises,
it cools and condenses into tiny water droplets.
These droplets collect together to form clouds.
↓
🌧️ Precipitation
When cloud droplets become heavy, they fall back to Earth as rain, snow, hail, or sleet.
↓
💦 Infiltration & Runoff
Rainwater flows into ponds, lakes, rivers, and oceans as runoff , or seeps into the ground as groundwater .
🧑‍🔬 Know a Scientist — Varahamihira
  • He was a sixth-century CE astronomer and mathematician .
  • He lived in Ujjaini (modern Ujjain), Madhya Pradesh.
  • His work Brihatsamhita gave methods to predict seasonal rainfall .
  • His predictions used cloud formation, wind patterns, and star positions.
  • This was an early scientific approach.
  • It helped understand the water cycle.

📋 NCERT Question 10 — Water Cycle Redistribution

The water cycle helps in redistribution and replenishment of water on Earth — justify this statement.
View Answer →
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