Drainage System - Solutions

 CBSE Class 11 Geography

NCERT Solutions
Chapter 19
Drainage System

1. Choose the right answer from the four alternatives given below:
(i) Which one of the following rivers was known as the 'Sorrow of Bengal'?

(a) The Gandak
(b) The Son
(c) The Kosi
(d) The Damodar

Ans. (d) The Damodar.

(ii) Which one of the following rivers has the largest river basin in India?

(a) The Indus
(b) The Brahmaputra
(c) The Ganga
(d) The Krishna

Ans. (c) The Ganga also referred to as the Ganges.

(iii) Which one of the following rivers is not included in 'Panchnad'?

(a) The Ravi
(b) The Chenab
(c) The Indus
(d) The Jhelum

Ans. (c) The Indus

(iv) Which one of the following rivers flows in a rift valley?

(a) The Son
(b) The Narmada
(c) The Yamuna
(d) The Luni

Ans. (b) The Narmada also called the Rewa, is a river in central India and the fifth longest river in the Indian subcontinent.

(v) Which one of the following is the place of confluence of the Alaknanda and the Bhagirathi?

(a) Vishnu Prayag
(b) Rudra Prayag
(c) Karan Prayag
(d) Deva Prayag

Ans. (d) Deva Prayag From here the river is called Ganga.

2. State the difference between the following.
(i) River Basin and Watershed

Ans. A river basin is also known as a catchment area, drainage basin, or catchment basin. It can have smaller sub-basins that combine to form a larger water basin. When rain falls or when ice and snow melts, the water that comes from them flows towards a river basin before exiting towards the river, lakes, oceans, or sea.

Landforms which are the divides or elevations that separate the river basin or catchment area are called watershed. They are also known as drainage divides because they divide the river system or river basins from other river systems. Other differences are as follows :

River Basin



The catchments of large rivers are called river basins.MeaningCatchment of small rivulets and rills are often referred to as watersheds.
River basins are larger in area.AreaWatersheds are smaller in area.

(ii) Dendritic and Trellis drainage pattern

Ans. dendritic drainage pattern occurs when the tributary systems subdivides headway like the limbs of a tree. These patterns usually form in horizontal sedimentary or in intrusive igneous rocks where the rock mass is reasonably homogeneous. A trellis drainage pattern occurs where subparallel streams erode a valley along the strike of less resistant formations. These beds are usually steeply dipping and may be part of a fold system. The tributaries often intersect at right angles where a notch called a water gap cuts through a harder formation. The meaning of both are given below:

Dendritic drainage patternBasisTrellis drainage pattern
Dendritic drainage system is a drainage pattern resembling the branches of a tree is known as “dendritic”. The drainage pattern of Northern plain is the example of such pattern.MeaningWhen the primary tributaries of rivers flow parallel to each other and secondary tributaries join them at right angles, the pattern is known as 'trellis'. This pattern is found in Himalayan mountains and the Eastern ranges (Purvanchal),

(iii) Radial and Centripetal drainage pattern.

Ans. radial drainage pattern occurs when the tributaries flow radially outward and downward from a central topographic high. This type of pattern is typical of volcanic cones, isolated hills, and elevated domes. Centripetal patterns are produced where drainage converges on a single outlet or sink, as in some craters, eroded structural domes with weak cores, parts of some limestone country, and enclosed desert depressions. Study the table given below:

Radial drainage patternBasisCentripetal drainage pattern
When the rivers originate from a hill and flow in all directions, the drainage pattern is known as ‘radial’. The river originating from the Amarkantak range present a good example it.  MeaningWhen the rivers discharge their waters from all directions in a lake or depression, the pattern is known as 'centripetal'. Sambhar lake of Rajasthan is the good example of it.

(iv) Delta and Estuary


Delta is a triangular land mass formed by depositional alluvium at the mouth of river  shapeEstuary is the sunken mouth of the river where the river where the rivers meets the sea forming the tunnel shaped zone where saline and fresh water mix.
They are formed on the tideless sea coast near the mouth of river where sediment brought by the rivers is deposited.FormationThey are result of strong currents and hightides at the mouth of river where no deposition takes place.
They are rich agriculture ground.SuitabilityThey are rich fishing ground and are suitable for inland transportation.
Rivers like Krishana, Kaveri, Mahanadi, Godavari form deltas.RiversNarmada and Tapi forms estuaries.

3. Answer the following questions in about 30 words.
(i) What are the socio-economic advantages of inter-linking of rivers in India?

Ans. Interlinking of Rivers is nothing but joining the rivers of the country by networks of canals and reservoirs. Interlinking of rivers in India was proposed for the first time during British Colonial rule. Indian rivers are of two types: perennial rivers in which there is water through out the year and peninsular rivers in which water is there in rainy seasons only. Rivers of India bear a large amount of water every year. But its distribution is not equal from the point of view of time and place. Most of the water gets wasted in floods during rainy seasons. It also causes loss of life and property. It ruins agriculture as well. At other places, there is situation of drought. Therefore, if rivers are connected to each other through canals, then the problems of floods and drought will get solved. It will also solve the problem of drinking water and millions of rupees will be saved. It will also lead to increase in productivity. It will improve economic condition of farmers.

  • Conservation of Ground water : Inter-linking of rivers leads to increase in the amount of surface water resources and eradicates the usage of ground water for irrigation. Increase in surface water resources leads to increase in the arable area.
  • Crop productivity and Food security: About 15% of ground water is used for food production every year in our country. Since a small amount of land is irrigated, by interlinking of rivers and increase in irrigation, crop production is improved and food security can be assured.
  • Health: Due to boring holes for ground water under large depths, the water extracted displayed high levels of arsenic, fluoride and other hazardous chemicals. In coastal areas, chances are obvious that contamination of saline water into the fresh ground water. Interlinking of surface water has no or little effects of health due to chemicals.
  • Employment: In the scenario of inter-linking of rivers, it leads to the fullest utilization of irrigation infrastructure available in India which in turn leads to more utilization of human resource and divert many of the jobless youth towards agriculture - the back bone of India.
  • Eradication of famine and prevention of flood: Since north and east areas receives bulk water through rain and floods, inter-linking leads to better management of water resources and bulk amounts of water can be first distributed to the non irrigated areas of north and east and then diverting the surplus water to south for irrigation, production and drinking.

(ii) Write three characteristics of the Peninsular rivers.

Ans. These rivers .originate in peninsular plateau and central highland. These are seasonal as it is dependent on monsoon rainfall. They reflect super imposed type of drainage pattern and rejuvenated resulting in trellis, radial and rectangular patterns. These rivers are smaller having fixed course with well-adjusted valleys. Their catchment area is relatively smaller basin. These rivers are old rivers with graded profile, and have almost reached their base levels.

4. Answer the following questions in not more than 125 words.
(i) What are the important characteristic features of north Indian rivers? How are these different from Peninsular rivers?

Ans. Important characteristics of north Indian rivers are as follows:
(i) Origin: They originate in Himalayan mountain covered with glaciers.
(ii) Nature of flow: These are perennial because they receive water from glacier and rainfall.
(iii) Drainage pattern: These are antecedent and consequently lead to dendritic pattern in plains.
(iv) Nature of river: It has long course, flowing through the rugged mountains experiencing headward erosion and river capturing; In plains it exhibits meandering and shifting of course.
(v) Catchment area: Its catchment areas include very large basins.
(vi) Age of river: These rivers are young and youthful. These are active and deepening in the valleys.
(vii) Loads: The rivers of North India carry maximum load as they flow over the soft rocks and alluvial plains.
(viii) Navigability: The Rivers of North India are navigable in their middle and lower courses.
These are different from peninsular rivers because these have following features:

  1. Place of origin: Peninsular plateau and central highland.
  2. Nature of flow: Seasonal as it is dependent on monsoon rainfall.
  3. Type of drainage: Super imposed, rejuvenated resulting in trellis, radial and rectangular patterns.
  4. Nature of river: Smaller, fixed course with well-adjusted valleys.
  5. Catchment area: Relatively smaller basin.
  6. Age of the river: Old rivers with graded profile, and have almost reached their base levels.

(ii) Suppose you are travelling from Haridwar to Siliguri along the foothills of the Himalayas. Name the important rivers you will come across. Describe the characteristics of any one of them.

Ans. While travelling from Haridwar to Siliguri along the foothills of the Himalayas, we shall come across Tons, Gomti, Saryu, Ramganga, Sharda, Gandak, Old Gandak, Kamla, Bagmati, Kosi and Ganga.
The Ganga is the most important river of lndia both from the point of view of its basin and cultural significance. It rises in the Gangotri glacier near Gaumukh which is 3,900 m high from sea level in the Uttarkashi district ofUttarakhand. It is known as the Bhagirathi in this region. At Devaprayag, the Bhagirathi meets the Alaknanda; hereafter, it is known as the Ganga.

The Ganga enters the plains at Haridwar. From here, it flows first to the south, then to the south¬east and east before splitting into two distributaries, namely the Bhagirathi and the Hugli. The river has a length of 2,525 km. It is shared by Uttarakhand (110 km) and Uttar Pradesh (1,450 km), Bihar (445 km) and West Bengal (520 km). The Ganga basin covers about 8.6 lakh sq. km area in India alone.

The Ganga river system is the largest in India having a number of perennial and non-perennial rivers originating in the Himalayas in the north and the Peninsula in the south, respectively. Yamuna joins the Ganga at Prayag (Allahabad). It is joined by the Chambal, the Sind, the Betwa and the Ken on its right bank which originates from the Peninsular plateau while the Hindan, the Rind, the Sengar, the Varuna, etc. join it on its left bank. Much of its water feeds the western and eastern Yamuna and the Agra canals for irrigation purposes.