Which of the following drainage systems drains the lands of Bihar ?

Question

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Correct — B, Ghagra. The Ghaghara rises on the northern slopes of the Himalaya in Tibet, in the Mapchachungo glaciers at about 3,962 metres, where it is called Mapcha Tsangpo; it runs 507 km through Nepal as the Karnali, that country's longest river; it enters India and crosses eastern Uttar Pradesh, where its lower course through Awadh is known as the Sarayu and gives Ayodhya its river; and it finally joins the Ganga at Revelganj, a little upstream of Chhapra in Saran district, Bihar. Its whole length is about 1,080 km, and it is the largest tributary of the Ganga by volume of water and the second longest after the Yamuna. Because that confluence lies inside Bihar, the river's last stretch and the low-lying country of Saran and Siwan on either side of it are part of Bihar's drainage — which is exactly what the question asks. The other three never touch the state. Bihar is drained almost wholly by the Ganga system, which enters the state near Chausa in Buxar district and cuts across it from west to east. The Himalayan rivers come in from Nepal to the north — Ghaghara, Gandak, Burhi Gandak, Bagmati, Kamla Balan, Kosi and Mahananda — and the peninsular rivers rise on the Chhotanagpur side to the south — Sone, Punpun, Falgu and Kiul. The Ghaghara is the westernmost of the northern group.

Why the other options are wrong — (a) The Mahanadi rises in the highlands of Chhattisgarh, crosses the Chhattisgarh plain past the Hirakud reservoir and flows through Odisha to the Bay of Bengal. Its basin lies entirely south of the Chhotanagpur plateau, which forms Bihar's southern watershed, so no part of Bihar drains into it.  (c) The Narmada rises at Amarkantak in Madhya Pradesh and flows west through the rift valley between the Vindhya and Satpura ranges into the Gulf of Khambhat. It is one of India's few major west-flowing rivers and drains the opposite side of the subcontinent from Bihar.  (d) The most tempting wrong answer, because the Yamuna is a Ganga tributary and Bihar is Ganga country. But the Yamuna merges with the Ganga at Prayagraj in Uttar Pradesh — hundreds of kilometres upstream of Bihar's western border — so it delivers its water to the Ganga before the Ganga ever reaches the state, and no Bihar land lies in the Yamuna's own basin.

Concept: Bihar's drainage is a three-part story arranged around the Ganga. The Ganga enters near Chausa in Buxar district and flows east across the middle of the state, splitting it into a north Bihar plain and a south Bihar plain. From the north come the Himalayan rivers, which rise in Nepal or Tibet, carry enormous silt loads out of young mountains, shift their channels and flood — the Ghaghara, Gandak (also called Narayani), Burhi Gandak, Bagmati, Kamla Balan, Kosi and Mahananda. From the south come the peninsular rivers off the old, hard rock of the Chhotanagpur plateau — Sone, Punpun, Falgu, Kiul — which are seasonal, carry less silt and have stable beds. The northern rivers are the reason Bihar is India's most flood-prone state; the Kosi, notorious for wandering westward across the plain, has long been called the Sorrow of Bihar. Note that a river 'drains' a state if that state's land sheds water into it, so a river's basin matters more than the length of channel visible on a map.

State PCS 2024 Q126 — Geography PYQ with Answer

State PCS 2024 Q126 — Geography PYQ with Answer