Questions
Answers
Drainage pattern refers to a design in which a river and its
tributaries form together from its source to its mouth.
Main types of drainage patterns:
Dendritic pattern:
1. Drainage pattern appearing like an irregular tree branch
is a dendritic pattern.
2. It develops in a terrain that has uniform lithology, and
where faulting and jointing are insignificant.
3. River Godavari, Mahanadi, and Kaveri are its examples.
1. Write a short note on drainage
patterns.
Trellis Pattern:
1. In the Trellis pattern, mainstream the primary
tributaries of rivers flow parallel to each other, and
secondary tributaries join them at right angles.
2. It develops where sedimentary rocks have been folded
or tilted and then eroded to varying degrees depending
on their strength.
3. Rivers in the Old fold mountains of the Singhbhum
region(Chotanagpur Plateau) serve as its examples.
Radial Pattern:
1. In a radial pattern, the streams radiate outwards from a
central high point.
2. Rivers like Narmada, Son, and Mahanadi originating
from Amarkantak Hills flow in different directions and
are good examples of radial patterns, mainstream.
Centripetal Pattern:
1. Similar to the radial drainage system, with the only
exception that radial drainage flows out versus
centripetal drainage flows in from all directions in a lake
or depression.
2. Streams of Ladakh, Tibet, and the Bagmati and its
tributaries in Nepal are examples.
Rectangular Pattern:
1. The mainstream bends at right angles and the
tributaries join at right angles creating rectangular
patterns.
2. Streams found in the Vindhya Mountains of India are
examples.
Pinnate Pattern:
1. This pattern resembles the veins of a leaf.
2. The drainage network of the upper Son and Narmada
rivers denotes the example of a pinnate drainage
pattern.
2. What is the difference between a
trellis drainage system and a
rectangular pattern?
3. What are Perennial rivers?
4. Why do the rivers change their
course?
Both the trellis and rectangular drainage pattern join the
master stream at right angles. But the angle of confluence in
the trellis pattern is determined by the strip and dip angle of
the rock beds while in the rectangular pattern, it is
determined by faults and fractures in the rock structures.
The perennial rivers are the rivers with a continuous flow
throughout the year such as the rivers Ganges, Indus, and
Brahmaputra.
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A river changes shape as it flows from its source to its
mouth.
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It occurs due to multiple factors like the amount of
water flow, fluctuation in water intensity, rate of
erosion, and sedimentation.
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The fast-flowing rivers are generally prone to silting up
as they surge down the hills and spread out on the
plains; thereby allowing sand and suspended matter to
deposit in their slower, wider depths. Over time, the
deposits create resistance, forcing the river to move to
an area of lower resistance. This is why rivers change
their courses.
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Nature's fury such as earthquakes, and landslides can
also change a river’s course.
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Human activities are also responsible for the change in
the river course.
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Kosi, the sorrow of Bihar floods frequently due to its
massive sedimentation.
A study by IIT Kanpur shows that along the banks of
Kosi 1,082 million tonnes of silt have been deposited in
it in the last 54 years. This is the highest amount of silt
deposition in any river of the Ganga Basin.
This silt causes the level of the riverbed to rise. As a
result, the natural longitudinal (straight) course of the
river is disturbed.
Therefore, the river searches for a lateral path (left or
right). As a result, it changes its course and breaches
the embankments on the new path it has created. The
breach of embankments causes floods.
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5. Why does the river Kosi flood so
frequently?
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6. Why does Assam flood every
monsoon?
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7. What is desilting?
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The Brahmaputra is both a lifeline and a threat to
Assam. The main reason is the sediments carried by the
river from Tibet Autonomous Region of China and
Arunachal Pradesh get deposited in the Assam plains.
During monsoons, due to heavy rainfall, river channels
get filled in no time, and as a result, a flood occurs.
With the encroachment of river banks, more and more
people are living close to the river and rampant
deforestation and cutting of hills have worsened the
situation.
Due to the impact of climate change on the Eastern
Himalayas, as glaciers melt faster the Brahmaputra
brings a huge volume of water, which leads to flooding
every year.
Desilting is the removal of fine silt and sediment
that gets collected in a river to restore its natural
capacity, without widening or deepening the river.
Desolation works have the potential to improve the
hydraulic performance of a river
Siltation results in the reduction in the carrying capacity
of rivers and results in floods and loss of created useful
storage. So desilting is done to reduce floods.
8. What constitutes a right bank or left Suppose a river flows from North to South, you should stand
bank of a river?
by facing the South as the river flows towards the South. Now
the bank on your right-hand side is the right bank, & the bank
on your left-hand side is the left bank.
9. What are the right and left bank
tributaries of the Indus River?
Indus is one of the largest river basins in the world, covering
an area of 11,65,000 sq. km and a total length of 2,880 km.
Important right bank Tributaries: Kabul River, Khurram,
Shyok, Gomal, Gilgit, and Sangar.
Important Left bank tributaries: Jhelum, Chenab, Ravi,
Beas, Satluj, Panjnad, and Zanskar.
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10. What is the Indus Water Treaty?
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The Indus Water Treaty (IWT) is a water distribution
treaty between India and Pakistan signed on September
19, 1960. The treaty was signed by then Prime Minister
Jawaharlal Nehru and Pakistan’s President Ayub Khan.
It was brokered by the World Bank.
According to the treaty, all the water of eastern rivers
( Sutlej, Beas, Ravi ) shall be available for unrestricted
use in India.
It gave the waters of the western rivers—the Indus,
Jhelum, and Chenab—to Pakistan. India can use the
water in western rivers for “non-consumptive” needs.
Non-consumptive means we can use it for irrigation,
storage, and even for electricity production.
11. What is the difference between a
tributary and a distributary?
A Tributary adds water to the main river. Yamuna is a
tributary of the Ganga. Distributaries take water away from
the main river. River Hoogly is a distributary of Ganga.
Prayag means the confluence of two or more rivers.
12. What are the Panch Prayags?
1. The Panch Prayag of Uttarakhand traces the route
carved by the Alaknanda River when it leaves its
Himalayan abode from the Satopanth glacier. It is
joined by the Dhauliganga River at Vishnuprayag,
near Joshimath.
2. Nandaprayag is the second confluence in a cascading
sequence, where the Alaknanda River is joined by the
Nandakini River.
3. The third confluence of the Alaknanda River is at
Karnaprayag, where the tragic hero of Mahabharata,
Karna, did penance to please Sun God. Here, Pindar
River joins Alaknanda.
4. Rudraprayag is the fourth confluence between
Alaknanda and the Mandakini River.
5. The fifth and final union takes place at Devprayag
where the Alaknanda River joins Bhagirathi forming the
mainstream which flows down to the plains.
River Ganga is the longest river in India and flows for around
1,569 miles (2,525 km) from the Himalayan Mountains to the
Bay of Bengal. The river has the second-greatest water
discharge in the world, and its basin is the most heavily
populated in the world with over 400 million people living in
the basin.
13. What are the important tributaries
of the River Ganga?
Major left-bank tributaries: Ramganga, Gomti, Ghaghara,
Gandak and Kosi.
Major right–bank tributaries: the Yamuna, Son, Punpun,
and Damodar.
14. What are Ephemeral rivers?
An ephemeral river is a river that only flows when there is rain
or snow has melted. The rest of the year there is just a dry
river bed with no water.
For example, the Luni River in Rajasthan. The Luni river in
Rajasthan originates near Ajmer and after flowing through the
Thar desert gets lost in the Rann of Kutch.
15. Write a short note on the Peninsular
rivers?
1. The Peninsular drainage system is older than the
Himalayan drainage. The broad, largely graded shallow
valleys characterized and the maturity of the rivers
proves the same.
2. The Western Ghats running close to the western coast
act as the water divide between the major Peninsular
rivers, discharging their water in the Bay of Bengal and
as small rivulets joining the Arabian Sea.
3. They are non-perennial rivers with a maximum
discharge in the rainy season.
4. Peninsular rivers are characterized by fixed courses
and the absence of meanders. The Narmada and the
Tapi are exceptions that flow through the rift valley and
east to west. They make estuaries.
5. Most of the major rivers of the peninsula such as the
Mahanadi, the Godavari, the Krishna, and the Cauvery
flow eastwards and drain into the Bay of Bengal. These
rivers make deltas in their mouths.
There are two main reasons for it:
16. Why do only the east-flowing rivers
form deltas and not the west-flowing
rivers?
1. Rivers of the Western Ghats flow through the peninsular
plateau. The Peninsula has a hard rock surface and
lacks alluvial material. So rivers do not carry a large
amount of sediments to deposit near the mouth of
the river to form deltas.
2. West-flowing rivers of the Western Ghats are small
streams. They flow rapidly from steep slopes and
merge into the Arabian Sea covering a very short
distance. They can form estuaries and not deltas.
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17. What is dredging?
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Dredging is the removal of sediments and debris from
the bottom of lakes, rivers, harbors, and other water
bodies to increase the depth of navigation channels.
Dredging is an activity of huge importance in the
maritime industry. It helps in safer voyages of vessels
by maintaining proper bottom clearance.
An Inland waterway is a network in the form of rivers, canals,
backwaters, and creeks that can be used for transportation in
place of or in addition to roads and rails.
18. What is inland water transport?
Challenges:
● Inadequate water channel Depth: Large vessels
cannot traverse without adequate water in the rivers.
This along with the seasonal dependency of rivers
makes the operation of many ports difficult.
● Harm to Aquatic Animals: Desilting the beds will
create muddy water and vessel engine noise and
movement will severely harm aquatic animals.
● Excessive Siltation: Deforestation and erosion activity
of the river leads to the problem of siltation making
navigation difficult. Without dredging its operation is
difficult.
But as it is environment friendly and cheaper than other
modes of transport, the Government of India is promoting
Inland Navigation.
19. Write a short note on the
interlinking of rivers.
The idea of interlinking rivers was first mooted by the Chief
Engineer of the Madras Presidency in 1919, Sir Arthur Cotton.
It envisages the transfer of water from water ‘surplus’ basins
where there is flooding, to water ‘deficit’ basins where there is
drought/scarcity, through inter-basin water transfer projects.
This project envisages the transfer of water from the
water-excess basin to the water-deficient basin by interlinking
37 rivers of India with a network of almost 3000 storage
dams. This will form a gigantic South Asian water grid. There
are two components to this project:
1. Himalayan Component
2. Peninsular Component
Benefits:
● Interlinking rivers is a way to transfer excess water
from the regions which receive a lot of rainfall to the
drought-prone areas. This way, it can control both
floods and droughts.
● This will also help solve the water crisis in many parts
of the country.
● It will help in hydropower generation.
Challenges:
● Environmental impact: The huge project will alter
entire ecosystems. The wildlife, flora, and fauna of the
river systems will suffer because of such displacements
and modifications.
● Inter-state disputes: Many states like Kerala, Sikkim,
Andhra Pradesh, etc. have opposed the river interlinking
project.
● Financial strain: The project is estimated to cost
around Rs.5.6 lakh crores.
20. What is Natural Vegetation?
Natural vegetation refers to a plant community that has
been left undisturbed over a long time, to allow its species to
adjust themselves to climate and soil conditions as fully as
possible.
Following are the forest types in India:
1. Tropical Evergreen and Semi-Evergreen forests
undergrowing.
2. Tropical Deciduous forests
3. Tropical Thorn forests
4. Montane forests
5. Littoral and Swamp forests.
21. What are the types of forests in
India?
22. Discuss the characteristics and
distribution of evergreen forests in
India.
Characteristics:
● The tropical wet evergreen forest in India is usually
found in areas receiving more than 250 cm of rainfall
and having a temperature of 15-30 degrees Celsius.
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They have a scarce presence of litter (organic matter
settling on the ground)
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Tropical evergreen forests are well stratified, with layers
closer to the ground and are covered with shrubs and
creepers, with short structured trees followed by a tall
variety of trees.
In these forests, trees reach great heights up to 60m or
above.
There is no definite time for trees to shed their leaves,
flowers, and fruition. As such these forests appear
green all year round.
They harbor many types of plants and animals.
The forests constitute an important part of the
environment and ecology.
Species found in these forests include rosewood,
mahogany, ebony, etc.
Distribution:
● They are found mostly near the equator.
● These forests are found in the western slope of the
Western Ghats, hills of the northeastern region, and the
Andaman and Nicobar Islands.
23. Discuss the characteristics and
distribution of semi-evergreen
forests in India.
Characteristics:
● Semi-evergreen forests have a mixture of evergreen
and moist deciduous trees.
● The under growing climbers provide an evergreen
character to these forests.
● The main species are white cedar, hollock, and kail.
Distribution:
● The semi-evergreen forests are found in the less rainy
parts of Western Ghats, hills of the northeastern region,
and the Andaman and Nicobar Islands regions, having
rainfall 200 to 250 cm
Deciduous forests are the most widespread forests in India.
They are also called monsoon forests.
Distribution: They spread over regions that receive rainfall
between 70-200 cm.
Based on the availability of water, these forests are further
divided into moist and dry deciduous.
24. Write a short note on Tropical
deciduous forests in India.
Moist deciduous forests
Conditions: Rainfall between 100-200 cm.
Regions: The eastern states along the foothills of the
Himalayas, eastern slopes of the Western Ghats, regions of
west Bengal, parts of Chattisgarh and Odisha.
Species: Teak, sal, shisham, hurra, mahua, amla, semul,
kusum, sandalwood, etc.
Dry deciduous forest
Conditions: Rainfall between 70-100 cm.
Regions: Most parts of India, Rainier areas of the peninsula,
plains of Uttar Pradesh, plains of Bihar, regions of the
Peninsular plateau, and the northern Indian plains.
Species: Tendu, palas, amaltas, bel, khair, axlewood, etc
Characteristics: Tropical thorn forests occur in areas that
receive rainfall less than 50 cm. These consist of a variety of
grasses and shrubs. In these forests, plants remain leafless
for most of the year and give an expression of scrub
vegetation.
Distribution: Semi-arid areas of southwest Punjab, Haryana,
Rajasthan, Gujarat, Madhya Pradesh, and Uttar Pradesh.
Species: Babool, ber, wild date palm, khair, neem, khejri,
palas, etc.
25. Discuss the characteristics and
distribution of thorn forests in India.
26. Write a short note on montane
forests found in India.
Montane ecosystems refer to any ecosystem found in
mountains. In mountainous areas, the decrease in
temperature with increasing altitude leads to a corresponding
change in natural vegetation.
Mountain forests can be classified into two types, the
northern mountain forests, and southern mountain
forests.
Northern mountain forests:
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The Himalayan ranges show a succession of vegetation
from the tropical to the tundra, which changes with
altitude.
Deciduous forests are found in the foothills of the
Himalayas.
It is succeeded by the wet temperate type of forests
between an altitude of 1,000-2,000 m. In the higher hill
ranges of northeastern India, hilly areas of West Bengal
and Uttaranchal, evergreen broadleaf trees such as oak
and chestnut are predominant.
Between 1,500-1,750 m, pine forests are also
well-developed in this zone, with Chir Pine as a very
useful commercial tree.
Deodar, a highly valued endemic species, grows mainly
in the western part of the Himalayan range.
Blue pine and spruce appear at altitudes of 2,225-3,048
m. At many places in this zone, temperate
grasslands are also found.
In the higher reaches, there is a transition to Alpine
forests and pastures. Silver firs, junipers, pines,
birch, rhododendrons, etc. occur between 3,000-4,000
m.
The southern slopes of the Himalayas carry a thicker
vegetation
cover
because
of
relatively
higher
precipitation than the drier north-facing slopes.
Higher latitudes: Tundra vegetation mosses and
lichens are found.
The southern mountain forests
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These include the forests found in three distinct areas
of Peninsular India viz; the Western Ghats, the
Vindhyas, and the Nilgiris.
As they are closer to the tropics, and only 1,500 m
above the sea level, vegetation is temperate in the
higher regions, and subtropical in the lower regions of
the Western Ghats, especially in Kerala, Tamil Nadu,
and Karnataka.
Shola forest: The temperate forests are called Sholas
in the Nilgiris, Anaimalai, and Palani hills. Some of the
other trees of this forest of economic significance
include magnolia, laurel, cinchona, and wattle. Such
forests are also found in the Satpura and the Maikal
ranges.
Figure: Shola forest
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27. What is transpiration?
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Like all living organisms, plants also require an
excretory system to discharge excess water from their
body. This process of elimination of excess water
from the aerial parts of the plant body is known as
transpiration.
Only a small amount of water absorbed by the plants is
utilized in growth and development. The rest is
eliminated in the form of transpiration.
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Littoral forests and Swamp forests are also called
wetland forests. Mangrove forests are a subtype of it.
Mangrove forests:
● Mangroves are a group of trees and shrubs that live in
the coastal intertidal zone. There are about 80 different
species of mangrove trees.
● All of these trees grow in areas with low-oxygen soil,
where slow-moving waters allow fine sediments to
accumulate.
● Mangrove forests only grow at tropical and subtropical
latitudes near the equator because they cannot
withstand freezing temperatures.
28. What are Littoral forests and
Swamp forests? Also, discuss
Mangrove forests.
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Mangrove forests stabilize the coastline, reducing
erosion from storm surges, currents, waves, and tides.
The intricate root system of mangroves also makes
these forests attractive to fish and other organisms
seeking food and shelter from predators.
Mangrove distribution in India:
29. What are tree cover and forest
cover?
The Ministry of Environment, Forest & Climate Change defines
‘forest cover’ in India as “all lands, more than one hectare
in an area with a tree canopy density of more than 10%”,
and ‘tree cover’ as “tree patches outside recorded forest
areas exclusive of forest cover and less than the minimum
mappable area of one hectare”.
The total forest cover of the country is 7,12,249 sq km which
is 21.67% of the geographical area of the country. The tree
cover of the country is estimated as 95,027 sq km which is
2.89% of the geographical area.
According to the India State of Forest Report (ISFR) 2019,
30. Which state in India has the highest
forest cover?
In terms of area:
Madhya Pradesh has the largest forest cover in the country
followed by Arunachal Pradesh, Chhattisgarh, Odisha, and
Maharashtra.
In terms of forest cover as a percentage of total
geographical area:
The top five States are Mizoram (85.41%), Arunachal Pradesh
(79.63%), Meghalaya (76.33%), Manipur (75.46%), and
Nagaland (75.31%).
Note: Punjab, Haryana, Rajasthan, Uttar Pradesh, Gujarat,
and Bihar have the lowest percentage of Forests in India.
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It is a type of vegetation composed primarily of
cone-bearing
needle-leaved
or
scale-leaved
evergreen trees, found in areas that have long
winters and moderate to high annual precipitation.
It consists mostly of conifers, trees that grow needles
instead of leaves, and cones instead of flowers. Conifers
tend to be evergreen, that is, they bear needles all year
long. These adaptations help conifers survive in areas
that are very cold or dry.
Precipitation in coniferous forests varies from 300 to
900 mm annually, with some temperate coniferous
forests receiving up to 2,000 mm. The amount of
precipitation depends on the forest location.
31. What are coniferous forests?
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Temperate coniferous forest is found in the middle and
upper elevations of the eastern middle Himalayas, in
western Nepal, Bhutan, and
northern-eastern Indian states.
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higher
elevations
of
For most of the year, the tundra is a cold, frozen
landscape that has a short growing season.
Tundra regions typically get less than 25 centimeters
(10 inches) of precipitation annually, which means
these areas are also considered deserts.
They have long, cold winters with high winds and
average temperatures below freezing for six to ten
months of the year.
Tundra forms in two distinct cold and dry regions.
Arctic tundra is found on high-latitude landmasses,
above the Arctic Circle—in Alaska, Canada, Russia,
Greenland, Iceland, and Scandinavia. Alpine tundra is
located at very high elevations atop mountains, where
overnight temperatures fall below freezing.
This type of climate is experienced in higher altitudes of
Kashmir, Himachal Pradesh, and Uttarakhand.
32. What is the tundra type of climate?
What is the type of vegetation
experienced in these regions?
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The tundra is a treeless polar desert but it supports
communities of sedges and heaths as well as dwarf
shrubs. It is known for large stretches of bare ground
and rock and patchy mantles of low vegetation such as
mosses, lichens, herbs, and small shrubs.