Q90. Which river has frequently shifted its course?
[WBCS Mains (2017)]
(A) Brahmaputra
(B) Ganga
(C) Teesta
(D) Kosi
Answer: (D) Kosi
Explanation: The Kosi has migrated across a broad alluvial fan in Bihar over historical time. This instability and associated flooding explain its reputation as the Sorrow of Bihar. Regional relief, river outlets and tributary connections help distinguish the surrounding drainage basin geographically.
Q89. Which is a right-bank tributary of the Ganga?
[WBCS Mains (2017)]
(A) Yamuna
(B) Gandak
(C) Kali
(D) Teesta
Answer: (A) Yamuna
Explanation: The Yamuna meets the Ganga from the southwest at Prayagraj, making it a right-bank tributary. Gandak and several Himalayan tributaries enter from the opposite side. The wider drainage network links Himalayan tributaries with major alluvial floodplains and downstream deltas.
Q88. Which river is not associated with the proposed Ganga–Cauvery link canal?
[WBCS Mains (2017)]
(A) Son
(B) Mahanadi
(C) Narmada
(D) Pennar
Answer: (C) Narmada
Explanation: Early eastward inter-basin transfer proposals linked rivers such as the Son, Mahanadi and Pennar. The west-flowing Narmada does not lie on this envisaged route. The wider drainage network links Himalayan tributaries with major alluvial floodplains and downstream deltas.
Q87. In which region is tank irrigation especially prevalent?
[WBCS Mains (2017)]
(A) Peninsular India
(B) Brahmaputra Valley
(C) Thar Desert
(D) Lower Ganga Plain
Answer: (A) Peninsular India
Explanation: The hard-rock terrain of peninsular India favours small reservoirs that collect seasonal runoff. Tanks historically support irrigation in parts of Tamil Nadu, Karnataka and Andhra Pradesh. Regional relief, river outlets and tributary connections help distinguish the surrounding drainage basin geographically.
Q86. Gersoppa Falls is located on which river?
[WBCS Mains (2017)]
(A) Godavari
(B) Sharavati
(C) Narmada
(D) Cauvery
Answer: (B) Sharavati
Explanation: The Sharavati cascades over the Western Ghats escarpment at Jog or Gersoppa Falls in Karnataka. Its water flows westward into the Arabian Sea. Waterfalls develop where river gradients shift abruptly, often across resistant rock or geological breaks.
Q85. With reference to Teesta, which statements are correct?
1. It has the same source as Brahmaputra.
2. Rangeet is its tributary from Sikkim.
3. It reaches the sea directly at the India–Bangladesh border.
[UPSC CSE Prelims (2017)]
(A) 1 and 3 only
(B) 2 only
(C) 2 and 3 only
(D) 1, 2 and 3
Answer: (B) 2 only
Explanation: Rangeet originates in Sikkim and joins the Teesta, so only statement 2 stands. Teesta has a separate Himalayan source and joins Brahmaputra drainage rather than flowing directly into the sea. Himalayan sediment, seasonal floodwater and heavy rainfall strongly shape the river channels and adjoining plains.
Q84. Where does the Luni River drain?
[WBCS Mains (2016)]
(A) Ganga Delta
(B) Godavari Delta
(C) Rann of Kutch region
(D) Gulf of Khambhat
Answer: (C) Rann of Kutch region
Explanation: Luni flows across western Rajasthan towards the Rann of Kutch. Its stream frequently disappears in saline flats, marking an inland-drainage landscape rather than a normal delta. Regional relief, river outlets and tributary connections help distinguish the surrounding drainage basin geographically.
Q83. Which city–river pairing is wrong?
[WBCS Mains (2016)]
(A) Srinagar–Jhelum
(B) Lucknow–Gomti
(C) Tiruchirappalli–Periyar
(D) Panaji–Mandovi
Answer: (C) Tiruchirappalli–Periyar
Explanation: Tiruchirappalli is situated on the Cauvery, whereas the Periyar is a major river of Kerala. The other pairings correctly identify the corresponding city rivers. Rivers shaped settlement, local trade routes and agriculture throughout the adjoining plains and valleys.
Q82. Which river is also called Vridha Ganga?
[WBCS Mains (2016)]
(A) Krishna
(B) Cauvery
(C) Godavari
(D) Mahanadi
Answer: (C) Godavari
Explanation: Vridha Ganga, meaning Old Ganga, is a traditional name for the Godavari. The river traverses large parts of the Deccan Plateau and forms a broad eastern delta. The wider drainage network links Himalayan tributaries with major alluvial floodplains and downstream deltas.
Q81. Which is not a tributary of the Krishna River?
[WBCS Mains (2016)]
(A) Tungabhadra
(B) Pennar
(C) Bhima
(D) Sina
Answer: (B) Pennar
Explanation: The Pennar has an independent drainage basin and reaches the Bay of Bengal in Andhra Pradesh. Tungabhadra and Bhima are major tributaries of the Krishna. Plateau slopes and underlying geological structures are especially important in determining peninsular drainage patterns.
