The other name of river Gandak is

Question

UnlockIAS · Accepted Answer

Correct — C, Narayani. The Gandak of Bihar and the Narayani of Nepal are the same river under two names. UNESCO's World Heritage description of Chitwan National Park uses both in a single line — the park's "core area lies between the Narayani (Gandak) and Rapti rivers to the north" — and again calls it "the Narayani (Gandaki) river, the third-largest river in Nepal, which originates in the high Himalayas and drains into the Bay of Bengal." India-WRIS, the Central Water Commission's basin wiki, traces the same water from the upstream end: the Gandak, "known as Kalie or Krishna Gandaki in the upper reaches", rises in the glaciers of southern Tibet at 7,620 m near the Tibet–Nepal border south-east of Dhaulagiri, gathers the Mayangadi, Bari and Trisuli, and "debouches into the plains of West Champaran district of Bihar at Triveni (Valmikinagar)". From there it runs south, forms the Uttar Pradesh–Bihar boundary for about 45 km, crosses Bihar and "finally joins the River Ganga opposite Patna". Its catchment totals 45,731 sq km — 5,687 sq km in Tibet, 30,882 in Nepal, 1,874 in Uttar Pradesh and 7,288 in Bihar — with roughly 380 km of course in Tibet and Nepal and 250 km in India. So the river carries three names down one continuous channel: Kali or Krishna Gandaki in the mountains, Narayani or Gandaki across the Nepal terai, and Gandak from Valmikinagar onwards. Naming it Narayani is naming the same river, which is exactly what the stem asks. Two further lines from the same Commission page close the door on the most tempting wrong answer. First, it defines the Gandak basin's own limits: "bounded on north by the Himalayas. On the south by the River Ganga, On the east by the Burhi Gandak Basin and on the west by the Ghagra Basin." A river cannot be bounded on the east by itself, so the Commission is stating in its own words that the Burhi Gandak is a neighbour, not an alias — and the Burhi Gandak page returns the compliment, describing that basin as bounded "on the west by the Gandak Basin". Second, the Commission's Ganga page lists "the Yamuna, the Ramganga, the Ghaghra, the Gandak, the Burhi Gandak, the Kosi, the Mahananda and the Sone" as eight separate principal tributaries, with the Gandak and the Burhi Gandak counted twice over as different rivers. Two more details worth carrying from the Gandak page: the catchment is trapezoidal in shape up to Triveni, and the source lies at about 29°18′ north — the far side of the Himalayan crest from Bihar, which is why the Gandak is a snow-fed river with a high-altitude regime while every one of the three distractors starts far lower down.

Why the other options are wrong — (a) A genuinely different river that merely shares part of the name. India-WRIS records that the Burhi Gandak rises from a spring of the Someshwar hills in West Champaran district at only 300 m and at about 27°29′ north — not in Tibet at 7,620 m — and is "known as Sikrchana in its upper reaches". It picks up the Masan, Harbora, Tilawe, Siriswa, Koria, Pasaha, Tiar and Hahwa, all with catchments in those same Someshwar hills, becomes the Burhi Gandak only after the Tiar joins it, enters Muzaffarpur, passes Darbhanga district near Pusa, crosses the Samastipur–Mansi line at the Rusera railway bridge, takes in the Bainty Balan in Khagaria and falls into the Ganga about 7 km east of Khagaria. Total length 579 km; catchment 12,180 sq km, of which 10,370 lie in Bihar and 1,810 in Nepal — against the Gandak's 45,731 sq km, so it is under a third the size. Decisively, the Commission maintains a separate Burhi Gandak basin and places it immediately east of the Gandak basin, and lists both as distinct principal tributaries of the Ganga.  (b) A separate north-bank tributary of the Ganga much further east — the Commission's own framing is that "after the river Gandak and the river Kosi meeting with the mighty river Ganga from the north, Mahananda, the most important tributary also meeting the river Ganga from the north", which places three distinct rivers in one sentence. India-WRIS describes the Mahananda as two streams: the right channel rises in the Nepal Himalaya, crosses Bihar, outfalls into the Ganga opposite Rajmahal and "is locally named as river Fulahar"; the left channel rises downhill at Darjeeling and runs about 400 km through Darjeeling, West Dinajpur and Malda into Bangladesh, reaching the Ganga near Godagarighat opposite Lalgola in Murshidabad. Average rainfall over that catchment is about 1,400 mm with 80% of it in four to five months, and the two channels merge in peak monsoon to waterlog Purnea and Katihar. So the Mahananda does have an alternative name — but it is Fulahar, not Narayani, and its basin never touches the Gandak's.  (d) The Punpun approaches the Ganga from the opposite bank, which makes it the easiest option to eliminate once you notice it. It rises in Palamu district of Jharkhand on the Chota Nagpur plateau and flows through Chatra, Gaya, Aurangabad, Jehanabad and Patna districts to meet the Ganga south-east of Patna. It has no Himalayan headwaters, no Nepali catchment and no snowmelt regime — it is fed only by monsoon rain on the plateau, so it can run near-dry in summer, the exact opposite of the Gandak, which carries Himalayan snowmelt through the lean season and meets the Ganga on the other side of the same city. North-bank and south-bank rivers are the first division of Bihar's drainage; a north-bank river cannot have a south-bank alias.

Concept: Himalayan rivers routinely change names along their course, because each stretch was named by the people living beside it rather than by a surveyor working end to end. The Gandaki system is the classic case: it rises as the Kali Gandaki in the high Himalaya, cutting the gorge between Dhaulagiri and Annapurna that is often called the deepest in the world; below the hills the Kali Gandaki and the Trishuli merge and the combined river becomes the Narayani, Nepal's third-largest; and at Triveni, where it debouches onto the plain at Valmikinagar in West Champaran, India calls it the Gandak. The same habit produces Tsangpo–Siang–Brahmaputra–Jamuna and Bhagirathi–Ganga–Padma. For Bihar the Gandak matters twice over: it is one of the four great north-bank rivers that carry Nepal's monsoon runoff onto a near-flat plain, and it forms the western edge of Valmiki Tiger Reserve before running down to the Ganga opposite Patna. The scale of that transfer is the point — 45,731 sq km of catchment, of which only 7,288 sq km lie in Bihar and 30,882 sq km in Nepal, so more than two-thirds of the water Bihar has to absorb is generated outside India, on slopes Bihar cannot manage. The Gandak Barrage at Valmikinagar, on the former Bhainsalotan site, completed in 1968 and 739 m long, is the single structure through which that whole system is regulated, and it is a joint India–Nepal work. The naming, in other words, is not a curiosity: the reason the river has a Nepali name at all is the reason Bihar's flood problem is a foreign-policy problem.

State PCS 2023 Q88 — Geography PYQ with Answer

State PCS 2023 Q88 — Geography PYQ with Answer