CHAPTER
3 WATER RESOURCES SPECIAL NOTES. CLASS X.
·
Important points to remember:
1.
Three-fourth of the earth’s surface is covered with water.
2.
97.5 per cent of the total volume of world’s water exists as oceans.
3.
Only 2.5 per cent is fresh water.
4.
Nearly 69 per cent of this freshwater occurs as ice sheets and glaciers in
Antarctica, Greenland and the mountainous regions of the world,
5.
30 per cent is stored as groundwater and less than 1 per cent is in lakes and
rivers.
6.
Freshwater is mainly obtained from surface run off and ground water.
7.
Water is continually being renewed and recharged through the hydrological cycle
thus water is a renewable resource.
8.
India receives nearly 4 per cent of the global precipitation and ranks 133 in
the world in terms of water availability per person per annum.
·
Multi-Purpose
River Projects and Integrated Water Resources Management
Important points to remember:
1.
In the first century B.C., Sringaverapura near Allahabad had sophisticated
water harvesting system channelling the flood water of the river Ganga.
2.
During the time of Chandragupta Maurya, dams, lakes and irrigation systems were
extensively built.
3.
Evidences of sophisticated irrigation works have also been found in
Kalinga,(Orissa), Nagarjunakonda (Andhra Pradesh), Bennur (Karnataka), Kolhapur
(Maharashtra), etc.
4.
In the 11th Century, Bhopal Lake, one of the largest artificial lakes of its
time was built.
5.
In the 14th Century, the tank in Hauz Khas, Delhi was constructed by Iltutmish
for supplying water to Siri Fort area.
6.
Dam is a barrier across flowing water that obstructs, directs or retards the
flow, creating a reservoir or lake.
7.
The Bhakra – Nangal project on Sutluj-Beas River is used both for hydel power
production and irrigation.
8.
Similarly, the Hirakud project in the Mahanadi basin integrates conservation of
water with flood control.
9.
The troubles faced by people owing to the flooding of Damodar River have given
this river a name as the river of sorrow.
10.Jawaharlal
Nehru proclaimed the dams as the ‘temples of modern India’.
11.He
called dams as temples because he thought they will integrate the
agriculture
and village economy with industrialization and urban economy.
Q.1.
Mention the important causes of water scarcity in some parts of the world ?
Ans.
Water scarcity in some part of the world is
caused by:
•Due
to the variations in seasonal and annual precipitation.
•water
scarcity is an outcome of large and
growing population and consequent greater demands for water,
•Water
scarcity in most cases is caused by over- exploitation, excessive use
•
unequal access to water among different social groups.
•Over-exploitation
of groundwater for growing more crops lead to falling groundwater levels,
•The
areas where water is sufficiently
available still suffers from water scarcity is due to water pollution.
Q
2 Although three-fourth of the earth’s surface is covered with water and water
is also a renewable resource ,even then some regions of the world suffer from
water scarcity. Explain any four reasons responsible for this.
1.About
97% of the total volume of world’s water exists as oceans. This water is saline and not suitable for direct
consumption.
2.Fresh
water availability is very limited. Of the 3% of the fresh water available,70%
of it is stored in glaciers and icesheets of the polar and mountainous regions
3.About
30% of fresh water stored in ground water is getting depleted due to excessive
use.
4.Availability
of water varies over time and space due to variations in seasonal and annual
precipitation
5.water
scarcity is an outcome of large and
growing population and consequent greater demands for water,
6.
Water scarcity in most cases is caused by over- exploitation, excessive use
7.Water
scarcity is also caused due to the bad quality of water. Much of the fresh
water has been polluted by the dumping of industrial, domestic waste,chemical
fertilizers,pesticides etc
Q.2
Why the conservation and management of our water resources is needed?
Ans.
The conservation and management of our water resources is necessary for:
1 To safeguard ourselves from health
hazards.
2
To ensure food security.
3 Continuation of our livelihoods and
productive activities.
4 To prevent degradation of our natural
ecosystems.
5 Over exploitation and mismanagement of
water resources will deplete water resource and cause ecological crisis.
Q.3
Who proudly announced the dams as the ‘temples of modern India’.
Ans:-
Jawaharlal Nehru.
Q
4 Why did Jawaharlal Nehru proclaimed
the dams as the temples of modern India?
Ans.
The reason Jawaharlal Nehru proclaimed them as temples are:
i.
Dams would integrate development of each sector of the economy.
ii.
Dams were thought of as the vehicle that would lead the nation to development
and progress.
iii.
They would develop agriculture and the village economy.
iv.
They would develop industries.
v.
They would help in the growth of the urban economy.
Q
5 What are dams and how do they help us in conserving and managing water?
Ans
:- A dam is a barrier across flowing water that obstructs, directs or retards
the flow, often creating a reservoir, lake or impoundment.“Dam” refers to the
reservoir rather than the structure. Most dams have a section called a spillway
or weir over which or through which it is intended that water will flow either
intermittently or continuously dams are built not just for irrigation but for electricity
generation,water supply for domestic and industrial uses, flood control,
recreation, inland navigation and fish breeding.
Q
6 What are Multi purpose river valley project ?
Ans
:- Multi purpose river valley projects are the dams or series of dams which are
constructed across rivers to impound water, which is later used for various purposes such as
Irrigation,Navigation, Generation of electricity,Pisciculture, Tourism etc.
Q
7 Why the Multi-purpose projects and large dams have come under great opposition?
Ans:-
The reasons are:
Affect natural flow of
running water:
i.
Hence, it causes excessive sedimentation at the bottom of the reservoir.
ii.
It results in rockier stream beds.
iii.
They also fragment rivers making it difficult for aquatic fauna to migrate,
especially for breeding.
Affect natural vegetation and soil:
i.
The reservoirs that are created on the floodplains also submerge the existing
vegetation and soil leading to its decomposition over a period of time.
ii.
The flood plains are deprived of silt, a natural fertiliser, further adding on
to the problem of land degradation.
Create conflicts:
i.
The dams create conflicts between people wanting different uses and benefits
from the same water resources.
ii.
Inter-state water disputes are also becoming common with regard to sharing the
costs and benefits of the multi-purpose project.
Cause of many social movements:
i.
They have been a cause of many new social movements like the ‘Narmada Bachao
Andolan’ and the ‘Tehri Dam Andolan’ etc.
Displacement of people:
i.
They results in the large-scale displacement of local communities.
ii.
Local people often had to give up their land, livelihood for the nation.
iii.
This leads to widening of the social gap
iv
.The local people are not benefiting from such projects.
Failure to control flood:
i.
The dams that were constructed to control floods have triggered floods due to
sedimentation in the reservoir and at the time of excessive rainfall.
ii.
It was also observed that the multi-purpose projects induced earthquakes,
caused waterborne diseases and pests and pollution resulting from excessive use
of water.
Change in cropping pattern:
i.
Availability of irrigation has also changed the cropping pattern.
ii.
Farmers have shifted to water intensive and commercial crops.
iii.
This has great ecological consequences like salinisation of the soil.
iv.
It has increased the social gap between the richer landowners and the landless
poor.
Q 8 Give examples of
traditional water harvesting systems developed in ancient India.
1.
In ancient India, along with the sophisticated hydraulic structures, there
existed an extraordinary tradition of water-harvesting system
2.
In hill and mountainous regions, people built diversion channels like the
‘guls’ or ‘kuls’ of the Western Himalayas for agriculture.
3
‘Rooftop rain water harvesting’was commonly practised to store drinking water,
particularly in Rajasthan
4
In the flood plains of Bengal, people developed inundation channels to irrigate
their fields
5.
In arid and semi-arid regions, agricultural fields were converted into rain fed
storage structures that allowed the water to stand and moisten the soil like
the ‘khadins’ in Jaisalmer and ‘Johads’in other parts of Rajasthan
Q 9 Why is the practice of
rooftop rainwater harvesting is on the decline in many parts of Rajasthan
?
Ans The practice of rooftop rainwater harvesting is on the decline in many parts of Rajasthan
as plenty of water is available due to the perennial Rajasthan Canal.
Q 10 Describe how traditional
rainwater harvesting is carried out in the semi-arid regions of Rajasthan.
Ans.
In semi-arid regions of Rajasthan traditional rainwater harvesting is carried
out asfollows :
i. Almost all the houses traditionally had
underground tanks or tankas for storing drinking water.
ii. The tanks could be as large as a big room;
iii. One household in Phalodi had a tank that
was 6.1 metres deep, 4.27 metres long and 2.44 metres wide.
iv. The tankas were part of the well-developed
rooftop rainwater harvesting system.
v. They were built inside the main house or
the courtyard.
vi. They were connected to the sloping roofs
of the houses through a pipe.
vii. Rain falling on the rooftops would travel
down the pipe and was stored in these underground ‘tankas’.
viii. The first spell of rain was usually not
collected as this would clean the roofs and the pipes. The rainwater from the
subsequent showers was then collected.
Q. 11. Name a village in
India which has earned the rare distinction of being rich in rainwater.
Ans Gendathur, a remote backward village in
Mysore, Karnataka.
Q.12 Describe how the drip irrigation system is
done in Meghalaya.
Ans.
200-year-old system of tapping stream and spring water by using bamboo pipes is
common in Meghalaya.
a) Bamboo pipes are used to divert perennial
springs on the hilltops to the lower reaches by gravity.
b) The channel sections, made of bamboo, divert
water to the plant site where it is distributed into branches, again made and
laid out with different forms of bamboo pipes.
c) The flow of water into the pipes is
controlled by manipulating the pipe positions.
d) If the pipes pass a road, they are taken
high above the land.
e) Reduced channel sections and diversion
units are used at the last stage of water application.
