Ganges-Brahmaputra Delta: World's Largest Delta in Bangladesh and West Bengal

The Ganges-Brahmaputra Delta (also Sundarbans Delta or Bengal Delta) spans 105,000 km² (41,000 sq mi) across Bangladesh (~60%) and India's West Bengal (~40%)—the world's largest delta.

Formation

Confluence of three Himalayan rivers:

• Ganges (Ganga): 2,525 km, sacred, populous basin
• Brahmaputra (Yarlung Tsangpo → Jamuna): 3,848 km, highest sediment load
• Meghna: Formed in Bangladesh by Surma/Kushiyara merger

Combined discharge: ~38,000 m³/s (monsoon) — 3rd globally after Amazon, Congo. Sediment load: ~1 billion tons/yr.

Ecology: The Sundarbans

World's largest mangrove forest (10,000 km²). UNESCO site. Bengal tigers, Irrawaddy dolphins, saltwater crocodiles, 260+ bird species. Cyclone buffer for inland millions.

Human Geography

• Population: 150–200M in delta zone (among densest rural populations on Earth)
• Agriculture: Rice (3 crops/yr), jute, tea, fish, shrimp
• Cities: Dhaka (22M), Kolkata (15M), Khulna, Barisal, Rajshahi
• Ports: Chittagong, Mongla, Kolkata/Haldia

Threats

• Sea-level rise (delta subsides 2–4 mm/yr; seas rise 3–4 mm/yr)
• Farakka Barrage (India) reduces dry-season flow → salinity intrusion
• Arsenic in groundwater (natural, affects 30M+)
• Cyclone intensification (Amphan 2020, Sidr 2007)
• Pollution: industrial, agricultural, municipal

The delta feeds and threatens hundreds of millions. Its fate is the climate crisis in microcosm.