NCERT Class 7 Science Chapter 16: Water YouTube Lecture Handouts

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NCERT Class 7 Science Chapter 16: Water

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  • 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 – 1/3rd 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 — Arveri, Ruparel, Sarsa, Bhagani and Jahazwali by constructing waterharvesting structures.

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