South America is blessed with some of the largest rivers and lakes in the world. They define the continent’s physical geography, economy, and ecology.

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🌎 4.1 Major River Systems

1. Amazon River 🌍

• Length: ~6,400 km (2nd longest after Nile).
• Origin: Nevado Mismi peak, Andes Mountains (Peru).
• Course: Peru → Colombia → Brazil → Atlantic Ocean.
• Mouth: Atlantic Ocean, estuary ~320 km wide.
• Tributaries: Madeira, Negro, Tapajós, Xingu, Purus, Ucayali, Marañón.
• Importance:
  • Largest river by discharge (20% of global freshwater to oceans).
  • Amazon Basin → World’s largest drainage basin (~7 million sq. km).
  • Supports Amazon rainforest → “Lungs of the Earth”.
  • Biodiversity hotspot → piranhas, pink dolphins, anacondas.
  • Navigation route (Manaus, Belém).

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2. Orinoco River

• Length: ~2,140 km.
• Origin: Parima Mountains (Venezuela–Brazil border).
• Course: Through Venezuela & Colombia → Atlantic Ocean.
• Importance:
  • Flows through Llanos grasslands → cattle ranching.
  • Hydropower & navigation.
  • Biodiversity → Orinoco crocodile, capybara.

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3. Paraná River

• Length: ~4,880 km.
• Countries: Brazil → Paraguay → Argentina.
• Importance:
  • Itaipu Dam (Brazil–Paraguay): One of the world’s largest hydroelectric dams.
  • Agriculture & transport.
  • Part of the La Plata Basin.

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4. Paraguay River

• Countries: Brazil, Bolivia, Paraguay, Argentina.
• Importance:
  • Major navigation route.
  • Supports Pantanal wetlands.

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5. Uruguay River

• Countries: Brazil, Argentina, Uruguay.
• Importance:
  • Joins Paraná to form Río de la Plata estuary.
  • Fertile agricultural lands, hydroelectric power.

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6. São Francisco River (Brazil only)

• Length: ~3,160 km.
• Importance: Irrigation, agriculture, hydroelectric dams in northeast Brazil.

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🌎 4.2 Major River Basins

1. Amazon Basin: Largest rainforest & biodiversity hub.
2. Orinoco Basin: Llanos grasslands, oil regions.
3. La Plata Basin (Paraná–Paraguay–Uruguay): Agriculture, dams, navigation.

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🌊 4.3 Major Lakes

1. Lake Titicaca

• Location: Peru–Bolivia border (Altiplano Plateau).
• Height: 3,812 m → World’s highest navigable lake.
• Importance:
  • Sacred to Inca civilization.
  • Uros people live on floating reed islands.
  • Shared water resource between Peru & Bolivia.

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2. Lake Maracaibo

• Location: Venezuela.
• Type: Technically a tidal bay connected to sea.
• Importance:
  • Oil-rich → Venezuela’s petroleum hub.
  • Known for Catatumbo lightning (unique weather phenomenon).

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3. Lake Poopó

• Location: Bolivia (south of Titicaca).
• Importance:
  • Endorheic basin (no outlet).
  • Shrank drastically in recent years due to climate change & mining.

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4. Other Lakes

• Llanquihue Lake (Chile): Glacial origin, near volcanoes.
• General Carrera Lake (Chile/Argentina): Famous for Marble Caves.

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📌 UPSC Key Pointers

1. Amazon River → Largest by volume; originates in Andes (Peru) and ends in Atlantic (Brazil).
2. Orinoco River → Flows through Llanos; Venezuela, Colombia.
3. Paraná–Paraguay–Uruguay → La Plata estuary; Itaipu Dam.
4. Lake Titicaca → Highest navigable lake; Peru–Bolivia.
5. Lake Maracaibo → Oil-rich, Venezuela.
6. Pantanal Wetlands (Paraguay River Basin) → world’s largest tropical wetlands.
7. River basins support hydroelectricity, transport, agriculture, biodiversity.