NDA (II) 2017 General Ability Test · Question 147 of 150

Correct — D, Vietnam. The Mekong rises on the Tibetan Plateau in Qinghai province of China and runs about 4,350 km through China, along the Myanmar and Thai borders, through Laos and Cambodia, and finally across the south of Vietnam, where it splits into a fan of distributaries and enters the South China Sea. That fan is the Mekong Delta, and it lies wholly within southern Vietnam, south-west of Ho Chi Minh City. It is one of the great rice bowls of Asia, and the region's dependence on the annual flood is why upstream dams and saltwater intrusion are such live issues there.

• (a)Thailand — The Mekong touches Thailand only as a border river, forming much of the frontier with Laos in the north-east. Thailand's own main river to the sea is the Chao Phraya, which builds a delta of its own at the Gulf of Thailand.
• (b)Cambodia — The nearest of the wrong answers. The Mekong does cross Cambodia, passing Phnom Penh where it meets the Tonle Sap river, and the river divides into its main distributary branches around there. But the delta proper — the built-up plain of silt at the river's mouth — lies downstream, across the border in Vietnam.
• (c)Myanmar — The Mekong only brushes Myanmar, along a short stretch of border in the Golden Triangle where Myanmar, Laos and Thailand meet. Myanmar's own great river is the Irrawaddy, whose delta is at the Andaman Sea.

The Mekong is the longest river of South-East Asia and passes through six countries — China, Myanmar, Laos, Thailand, Cambodia and Vietnam. It rises on the Tibetan Plateau, runs in a deep gorge through Yunnan, then broadens through the lowlands of Indo-China. In Cambodia it is linked to the Tonle Sap lake by a river that reverses its flow with the seasons, filling the lake in the monsoon and draining it in the dry season. It reaches the sea through the delta in southern Vietnam.

The dependable way to get the mouth of any river right is to name the sea it enters and then the country that owns that shore. The Mekong empties into the South China Sea, and the coast at that point is Vietnamese. It is worth keeping the neighbouring deltas apart at the same time, because examiners set them against one another: the Irrawaddy delta belongs to Myanmar on the Andaman Sea, the Chao Phraya delta to Thailand on the Gulf of Thailand, and the Red River delta to northern Vietnam. Note also which country the Mekong does not reach at all — Malaysia — a point the UPSC has itself tested.

• The Mekong rises on the Tibetan Plateau in Qinghai, China, and runs about 4,350 km.
• It passes through China, Myanmar, Laos, Thailand, Cambodia and Vietnam.
• Its delta lies in southern Vietnam and it empties into the South China Sea.
• In Cambodia the river is linked to the Tonle Sap lake by a channel that reverses direction with the seasons.
• The Mekong does not flow through Malaysia, and Myanmar touches it only along a short border stretch.

• Placing the delta in Cambodia because the river's branching begins near Phnom Penh.
• Confusing the Mekong with the Irrawaddy or the Chao Phraya, which have deltas of their own.
• Assuming the Mekong reaches Malaysia; it stops well north of the peninsula.

Rivers are asked as a where-is-the-delta item, as a country-it-does-not-pass-through item, or as a river-to-sea pairing.

• practice — not a real PYQ

  The Mekong finally empties into

  • (a)the Andaman Sea
  • (b)the Gulf of Thailand
  • (c)the South China Sea
  • (d)the Java Sea

  Answer(c) the South China Sea — through the delta in southern Vietnam.

• practice — not a real PYQ

  The Tonle Sap, a lake whose connecting river reverses its flow with the seasons, lies in

  • (a)Laos
  • (b)Cambodia
  • (c)Vietnam
  • (d)Thailand

  Answer(b) Cambodia — it fills from the Mekong in the monsoon and drains back to it in the dry season.