NCERT Class 7 Science Chapter 16: Water YouTube Lecture Handouts

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NCERT Class 7 Science Chapter 16: Water

  • What are bawris?
  • What is aquifer?
  • Differentiate filtration and infiltration?

LET՚s BEGIN! !

  • 22 March – World Water Day
  • As per UN – 50 liters water per person per day
  • This is equal to 2.5 buckets/person/day
  • Shortage of water – dry taps, marches, protests, water trains, water queue
  • Future – 1βŸ‹3rd population might face water scarcity
  • Year 2003 was observed as the International Year of Freshwater to make people aware of this dwindling natural resource.

Water Availability

  • 71% earth surface is water
  • Most water in seas, oceans, lakes, ice caps
  • Most water not fit for human consumption
  • Bucket – 20 liters (water on earth) - [except bath mug is saline water]
  • Bath Mug – 0.5 liter (total freshwater) – [except glass is frozen form in glaciers, ice caps and permanent snow]
  • Glass - 0.15 liter (usable water as groundwater) -
  • Spoon - 0.012 liter (water in lakes and rivers)
  • Therefore, 0.006% of all water found on the earth is usable
  • Three forms of water – solid, liquid and gas
  • Water Cycle

Groundwater

  • Moisture in soil indicates presence of groundwater
  • Dig deeper and reach water table
  • Water table - where all the space between particles of soil and gaps between rocks are filled with water
  • The water found below the water table is called groundwater
  • Infiltration – seeping of water into the ground (this recharges the ground water)
  • Aquifer - At places the groundwater is stored between layers of hard rock below the water table – water is pumped out through tubewells
  • Borewell been dug to reach the water table
  • Reasons for depletion of water table
  • Increasing population
  • Scanty rainfall
  • Deforestation
  • Decrease in effective area for water seepage
  • No seepage through pucca floor
  • Increasing industries
  • Agricultural activities – irrigation

Distribution of Water

  • Uneven
  • Floods and droughts
  • Interlinking of rivers

Water Management

Well planned pipe system

No leakage or water gushing out

Prevent wastage

Prevent mismanagement

Recharge ground water – rainwater harvesting

Bawris – traditional way for water collection (revival)

Drip irrigation - narrow tubings which deliver water directly at the base of the plant

Check dams to increase percolation

Wells

Stop leakage from taps

Water is must for life

Alwar district into a green place- revived five dried-up

rivers β€” Arveri, Ruparel, Sarsa, Bhagani and Jahazwali by constructing waterharvesting structures.

✍ Mayank