Hinglish

The Water Cycle and Groundwater

Class 7 Science · Chapter 7: Heat Transfer in Nature · NCERT Curiosity section 7.4

Learn

Wet clothes dry faster on a sunny day because the Sun's heat speeds up evaporation. The same heat lifts water from seas, rivers and lakes as vapour; plants add vapour too through transpiration. Rising vapour cools and condenses into clouds, which bring rain, snow or hail: precipitation.

This endless loop, up as vapour and down as precipitation, through soil, rocks and plants and back to water bodies, is the water cycle. It refills rivers and lakes and keeps the total water on Earth the same. Centuries ago, the astronomer Varahamihira of Ujjain described ways to predict seasonal rain from clouds, winds and the sky.

Kabir fills three cut bottles with clay, sand and gravel and pours 200 mL of water into each. Water rushes through gravel, drips through sand and barely gets through clay. Water seeping into the ground is infiltration; it is fastest where spaces are wide and connected. Stored in pores of underground rock and sediment, it becomes groundwater, held in layers called aquifers that wells tap.

Groundwater is not unlimited. Too many borewells, fewer trees and more concrete that stops rain soaking in are making it fall. Rainwater harvesting and recharge pits help refill it. In cold Ladakh, people build ice stupas: winter stream water sprayed into freezing air piles up as tall cones of ice that melt slowly in spring, just when farms need water.

Explore: how fast does water seep?

  1. Pour water through each and sort by seepage.

Explore: the water cycle.

  1. Put the stages in order.

Remember

  • The Sun drives the water cycle: evaporation and transpiration, condensation, precipitation, and return.
  • Infiltration stores groundwater in aquifers; harvesting rain and recharge pits help refill them.

Quick check

Underground layers of rock and sediment that hold water are called …

  1. aquifers
  2. glaciers
  3. clouds
  4. craters
Answer

aquifers. Wells and borewells draw water from aquifers.

Think about it

Why do floods happen more easily in a fully paved city than in a village with fields?

One answer

Concrete stops infiltration, so rainwater cannot soak into the ground and runs off over the surface instead.

Practice

Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.