Class 7th Science Chapter 16 , Water PPt , (19 Slides 9 MB), Short PPt Water,

1. Class 7th

2. water

3. How much water is Available
 About 71%of the earth’s surface is covered with
water.
 Almost all the water on the earth is contained in
the seas and oceans, rivers, lakes ice caps, as
groundwater and in the atmosphere.
 Most of this water is not fit for human
consumption. The water that is fit for use is
freshwater.

4. Form of water
 Water on the earth has been maintained for millions
of years by various processes which make the water
cycle.
 When water circulates through the water cycle it can
be found in all the three from , solid, liquid and gas-
at any given time somewhere on the earth.
 The solid form, snow and ice, is present as ice caps at
the poles of the earth, snow- covered mountains and
glaciers.

5.  liquid water is present in oceans, lakes, rivers, and
even underground.
 The gaseous from is the water vapour present in the
air around us.
The continuous cycling of Water among its three from
keep the total amount of water on the earth constant
even the whole world is using it.

6. Fig.1 Water cycle
Infiltration
Ground water
Evaporation
Transpiration
Condensation
Clouds
Precipitation

7. Ground water
 The ground has a large storage of water inside it. If we
dig deeper and deeper below the earth, we will reach a
level where all the space between particles of soil and
gaps between rocks are filled with water.
 The upper limit of layer is called the water table.
The water table varies from place to place, and it may
even change at a given place.

8.  The water found below the water table is called ground
water.
 The rainwater and water from other sources such as rivers
and ponds seeps through the soil and fills the empty spaces
and cracks deep below the ground.
 The process of seeping of water into the ground is called
Infiltration.
 The groundwater is stored between layers of hard rocks
below the water table is called Aquifer.

9. Fig. 2 Ground Water
Hand pump
Stream or Lake
Aquifer
Water Table

10. Depletion if water table
 Water table may go down if the water is not
sufficiently replenished.
 It is due to increasing population, industries,
decrease of seepage area for seepage of rainwater,
agricultural activities, deforestation and scanty
rainfall.

11. Increasing population
 Increasing population creates demand for
construction of houses, shops, offices, roads and
pavements.
 This decreases the open areas like parks and
playgrounds. This in turn, decreases the seepage of
rainwater into the ground.
 A huge amount of water is needed for construction
work and all the water is drowned from ground.

12. Increasing industries
 Water is used by all industries. Almost everything that
we use needs water somewhere in its production
process.
 The number of industries is increasing day by day.
 Water used by most industries is drawn from ground.

13. Agricultural activities
 A majority of farmers in in India depend upon rains for
irrigating their crops. Irrigation system like canals are there
only in a few places.
 These system may suffer from lack of water due to plenty of
rainfall. So farmers have to use groundwater for irrigation.
 Population pressure on agriculture forces increasing use of
groundwater day by day. This resulting depletion of water
table.

14. Distribution of water
 Some place have good amount of rain and at some
pace there are deserts which have scanty rainfall.
 India is a vast country and the rainfall is not the same
everywhere. Some regions have excessive rain while
some other have very little rain fall.
 Excessive rain cause floods, whereas the absence of
rains results in droughts.

15. Water management
 Most of the water that we get as rain fall just flows
away. The rainwater can be used to recharge the
groundwater.
 This is referred to as water harvesting or rainwater
harvesting.
 Many place in india an age old practice of water
storage and water recharge like the Bawris.
 Bawri was the traditional way of collecting water.

16. Fig. 3 Annual rainfall in INDIA

17.  The Bawris are also used today, there was the time
when people forgot the importance of Bawris.
 Drip Irrigation is a water saving Irrigation system. In
this system, water falls on the roots of the plants drop
by drop by the help of pipes.
 We can also play an important role in saving of water.
 We should turn off taps while bathing and brushing.
 We should map the floor instead of washing.
 We should use a bucket instead of bathtub or shower
for bathing

18. Fig. 4 Drip Irrigation System

19. Water is a very important and precious resource. Save
water save life.
Thank you for Watching
My Little Creation