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?
LETΥs BEGIN! !
- 22 March β World Water Day
- As per UN β 50 liters water per person per day
- This is equal to 2.5 buckets/person/day
- Shortage of water β dry taps, marches, protests, water trains, water queue
- Future β 1β3rd 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 β 20 liters (water on earth) - [except bath mug is saline water]
- Bath Mug β 0.5 liter (total freshwater) β [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 β 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 β 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 β 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 β 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 β rainwater harvesting
Bawris β 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.
β Mayank