UPPSC 2024 Prelims GS Paper-I · Question 77 of 150

Correct — D, Mekong river – South-West. The Mekong is the odd one out because it runs the other way along the east–west axis: it rises on the Tibetan Plateau in Qinghai, cuts south through Yunnan as the Lancang, then continues broadly south and south-east along the Myanmar–Laos and Laos–Thailand borders, through Cambodia, and ends in a delta in southern Vietnam that empties into the South China Sea. Every leg of that ~4,350 km course carries the water southward and eastward — never towards the south-west. A river flowing south-west from Tibet would have to head for the Bay of Bengal, which is the Irrawaddy and Salween story, not the Mekong's. So the pair 'Mekong – South-West' is the one that is not correctly matched, and (d) is the marked answer. The way to keep this straight is to fix the mouth rather than the middle: Amur → Strait of Tartary and the Pacific in the far north-east; Syr Darya → the shrunken northern Aral Sea in the north-west of its basin; Angara → the Yenisei, reached by first running due north out of Lake Baikal; Mekong → the South China Sea in the far south-east. Once the mouths are fixed, the compass directions follow without memorising them.

• (a)Amur river – North-East — Correctly matched, so it cannot be the answer. The Amur proper begins where the Shilka and the Argun meet on the Russia–China frontier. It first runs east, arcs south-east for a few hundred kilometres, and then — after the Songhua (Sungari) joins it and it passes Khabarovsk — turns decisively north-east, flowing north-north-east through a wide valley in eastern Russia before swinging east to its mouth at Nikolayevsk-na-Amure. From there it enters the Pacific through the Strait of Tartary, which links to the Sea of Okhotsk. Its net displacement from source to mouth is emphatically towards the north-east, which is exactly what the option says.
• (b)Syr Darya – North-West — Correctly matched. The Syr Darya is formed in the Fergana Valley where the Naryn and the Kara Darya, both fed by the Tian Shan, come together. From there it runs for about 2,256 km 'west and north-west' through Uzbekistan, the Sughd province of Tajikistan and southern Kazakhstan, ending in the northern remnant of the Aral Sea near Kazaly. It is the classic north-westward Central Asian river — its twin, the Amu Darya, does the same thing further south, and the two together once kept the Aral Sea alive.
• (c)Angara river – North — Correctly matched. The Angara is the single river that flows out of Lake Baikal — over three hundred streams feed the lake, but only the Angara drains it, leaving near the settlement of Listvyanka. It then runs north past Irkutsk, Angarsk, Bratsk and Ust-Ilimsk, crosses the Angara Range, and only in its final stretch turns west to join the Yenisei near Strelka. 'North' is therefore the right label for its dominant direction, and the later westward swing does not change that.

The direction a river takes is decided by the regional slope of the land, not by any preference of its own, so a river's compass heading is really a statement about the tilt of the continent it drains. Northern Asia tilts towards the Arctic, which is why the Ob, the Yenisei and the Lena — and the Angara that feeds the Yenisei — all run north. The Central Asian interior is a closed basin with no outlet to the sea, so the Amu Darya and the Syr Darya run inward and north-west to the Aral Sea and die there. The Far Eastern margin drains to the Pacific, taking the Amur north-east. And the Tibetan Plateau, the highest source region on Earth, sheds water in every direction — the Indus and Sutlej west, the Brahmaputra east then south, and the Salween, Mekong and Yangtze south and south-east through the deep parallel gorges of Yunnan.

UPPSC's 'River – Direction' pair is really a mouth question in disguise. Nobody carries the compass bearing of the middle reach of the Amur in their head; what a prepared candidate carries is where each river ends. Work backwards from the mouth and three of the four pairs settle themselves — Strait of Tartary is north-east of the Shilka–Argun confluence, the Aral Sea is north-west of the Fergana Valley, the Yenisei is reached by heading north out of Baikal. The Mekong is where the trap lives, because 'south' is right and 'south-west' looks close enough to survive a fast reading. It does not: from Tibet the Mekong tracks south-east down the Indochina peninsula to the South China Sea, and the delta sits in southern Vietnam, which is about as far east as the peninsula goes. Any river leaving the plateau to the south-west would end in the Bay of Bengal instead. Read the compass word, not the hemisphere word.

• Mekong — rises on the Tibetan Plateau (Qinghai, China), flows through China, Myanmar, Laos, Thailand, Cambodia and Vietnam, and empties into the South China Sea through a delta in southern Vietnam; about 4,350 km. Its net course is south and south-east, not south-west.
• Amur — forms at the confluence of the Shilka and the Argun, flows east, arcs south-east, then turns north-east past Khabarovsk and reaches the Pacific through the Strait of Tartary near Nikolayevsk-na-Amure; about 4,444 km.
• Syr Darya — begins where the Naryn and the Kara Darya join in the Fergana Valley and flows about 2,256 km west and north-west through Uzbekistan, Tajikistan (Sughd) and southern Kazakhstan to the northern remnants of the Aral Sea.
• Angara — the only outflow of Lake Baikal, leaving at Listvyanka; runs north past Irkutsk, Angarsk, Bratsk and Ust-Ilimsk, then turns west to join the Yenisei near Strelka.
• The Mekong delta lies in southern Vietnam, not in Cambodia — this is the single most-tested fact about the river, and UPPSC itself used it in 2021.

• Reading 'south-west' as if it were 'south-east'. In a NOT-correctly-matched pair question the single word that breaks the pair is often just one compass point away from the truth.
• Believing the Angara flows into Lake Baikal. It is the lake's only outlet; the Selenga is the biggest river flowing in.
• Placing the Mekong delta in Cambodia. The delta is in southern Vietnam — Cambodia holds the Tonle Sap and the river's middle course.

UPPSC likes the compact pair format — river paired with direction, with a sea, or with a city. UPSC prefers 'Consider the following pairs: River — Flows into' or 'the great Asian river X does not run through'. Either way the examinable unit is source region, countries crossed, and mouth.

• practice — not a real PYQ

  Which one of the following rivers is the only river flowing out of Lake Baikal?

  • (a)Selenga
  • (b)Angara
  • (c)Lena
  • (d)Yenisei

  Answer(b) Angara — it leaves Baikal near Listvyanka and flows north, later turning west to join the Yenisei; the Selenga is the lake's largest inflowing river, not an outlet.

• practice — not a real PYQ

  Which one of the following pairs (River – Water body into which it finally drains) is correctly matched?

  • (a)Amur – Caspian Sea
  • (b)Syr Darya – Aral Sea
  • (c)Angara – Sea of Okhotsk
  • (d)Mekong – Andaman Sea

  Answer(b) Syr Darya – Aral Sea — it ends in the northern remnant of the Aral. The Amur reaches the Pacific through the Strait of Tartary, the Angara ends in the Yenisei, and the Mekong drains to the South China Sea.