UPSC CSE Prelims
Major Rivers and Lakes Previous Year Questions (PYQs)

Detailed Explanation:

📘 Explanation (English):

Statement 1 is correct. Lake Turkana is the world's largest permanent desert lake and the largest alkaline lake.

Statement 2 is incorrect. The lake is located mainly in northern Kenya and extends into Ethiopia. It is part of the Great Rift Valley, not South Sudan or the Sahara Desert.

Statement 3 is correct. Lake Turkana National Parks are a UNESCO World Heritage Site, and the lake is known as the “Jade Sea” because of its greenish-blue waters.

Lake Turkana

• Lake Turkana is an important Rift Valley lake in East Africa.

• It is famous for its alkaline water, rich fossil sites, UNESCO status, and the nickname “Jade Sea.”

Detailed Explanation:

Correct Answer: ✅ Option 4 (None)

The Equator does not pass through any of the three given water bodies. Although Lake Tanganyika is located in East Africa near the Equator, it lies entirely south of it. Tonlé Sap is located in Cambodia in Southeast Asia, while Patos Lagoon is situated in southern Brazil, both far from the Equator.

❌ Statement I is Incorrect: Lake Tanganyika lies south of the Equator and does not cross it.

❌ Statement II is Incorrect: Tonlé Sap is located in Cambodia, north of the Equator.

❌ Statement III is Incorrect: Patos Lagoon is located in southern Brazil, well south of the Equator.

Short Notes: Important Lakes and Lagoons of the World

• Lake Tanganyika is one of the world's deepest freshwater lakes.

• Tonlé Sap is Southeast Asia's largest freshwater lake.

• Tonlé Sap is known for its seasonal reversal of river flow.

• Patos Lagoon is the largest lagoon in Brazil.

• The Equator passes through countries such as Brazil, Ecuador, Colombia, Kenya, Uganda, and Indonesia.

• Major equatorial lakes include parts of Lake Victoria, but not Lake Tanganyika.

• Location-based questions are common in UPSC Geography.

Detailed Explanation:

Answer: Option 1 — Cameroon

The Congo Basin is a vast sedimentary basin in Central Africa centered around the Congo River. It primarily spans across six countries: Cameroon, Central African Republic, Democratic Republic of the Congo, Republic of the Congo, Equatorial Guinea, and Gabon. Among the given options, only Cameroon is part of the Congo Basin, while Nigeria lies to the west, and South Sudan and Uganda are located to the east of the basin.

📝 Short Notes: Congo Basin

• Location: Central Africa, in the West Equatorial Africa region
• Main Feature: Sedimentary basin of the Congo River, the world's second-largest river basin by area
• Countries: Six main countries — Cameroon, Central African Republic, Democratic Republic of the Congo, Republic of the Congo, Equatorial Guinea, and Gabon
• Significance: Contains the world's second-largest tropical rainforest (after Amazon), crucial for global climate regulation
• Biodiversity: Home to over 10,000 plant species, 1,000 bird species, and 400 mammal species including gorillas, chimpanzees, and forest elephants
• Climate: Equatorial climate with high rainfall throughout the year

Detailed Explanation:

Answer: Option 2 — Lake Faguibine

Lake Faguibine in Mali, West Africa, was once one of the largest lakes in the region, fed by the Niger River during seasonal floods and spanning approximately 590 square kilometers in 1974. Due to declining precipitation from the late 1980s, increasing aridity, and changing climate patterns, the lake gradually dried up and has remained nearly dry since the late 1990s, turning the area into a desert despite the resumption of normal rainfall after 2000.

Why other options are incorrect:

• Lake Victoria: Located in East Africa (not West Africa), it is the largest lake in Africa and remains filled with water.
• Lake Oguta: Located in Nigeria, West Africa, it is still a functional freshwater lake and has not turned into a desert.
• Lake Volta: Located in Ghana, West Africa, it is one of the world's largest artificial reservoirs by surface area and remains filled with water from the Volta River.

📝 Short Notes: Desertification and Lake Desiccation in Africa

• Lake Faguibine: Located in Mali, West Africa; once covered 590 sq km (1974); dried up by late 1990s due to reduced rainfall and climate change.
• Desertification in Sahel: The Sahel region, including Mali, has experienced severe desertification due to climate variability, overgrazing, and land degradation.
• Impact on livelihoods: Drying of Lake Faguibine destroyed traditional fishing, agriculture, and livestock herding activities.
• Climate patterns: Despite return of normal rainfall post-2000, the lake has not recovered, indicating irreversible environmental changes.
• Other African lakes under threat: Lake Chad has also shrunk by over 90% since the 1960s due to similar climatic and anthropogenic factors.

Detailed Explanation:

Answer: Option 3 — 3 and 4 only

This question tests the knowledge of major world rivers and their drainage systems. Out of the four pairs, only pairs 3 and 4 are correctly matched, while pairs 1 and 2 contain errors regarding the water bodies into which these rivers flow.

❌ Pair 1 – Incorrect: The Mekong River flows into the South China Sea, not the Andaman Sea. It originates in the Tibetan Plateau and passes through China, Myanmar, Laos, Thailand, Cambodia, and Vietnam.

❌ Pair 2 – Incorrect: The Thames River flows into the North Sea, not the Irish Sea. It flows entirely within England.

✅ Pair 3 – Correct: The Volga River, Europe's longest river, originates in Russia and correctly flows into the Caspian Sea.

✅ Pair 4 – Correct: The Zambezi River originates in Zambia and flows through several countries before emptying into the Indian Ocean via Mozambique.

📝 Short Notes: Major World Rivers and Their Drainage