Rainfall and Forest Types

Where India gets rain and why — and how rainfall and altitude decide the forest, from evergreen to thorn, alpine and mangrove.

On this map (24)

Mawsynram — the wettest place · Meghalaya — Rain · ~1,180 cm a year. Highest average annual rainfall on Earth, about 1,180 cm
Agumbe — windward side of the Western Ghats · Karnataka — Rain · 700+ cm. The Arabian Sea branch hits the Western Ghats head-on and rises → very heavy rain on the WEST (windward) slope
Rain-shadow Deccan — east of the Western Ghats · Maharashtra — Rain · 50–60 cm. Once over the Ghats, the air sinks and warms, so the EAST side stays dry — the rain-shadow
Jaisalmer — the dry west of the Thar · Rajasthan — Rain · under 15–20 cm. The Aravallis lie parallel to the Arabian Sea branch, so they do not stop it — the wind passes over the Thar without rain
Leh — cold desert behind the Himalaya · Ladakh — Rain · under 10 cm. The Great Himalaya blocks the monsoon, so Ladakh gets under 10 cm — a COLD desert
Chennai — the Tamil Nadu coast gets rain in winter · Tamil Nadu — Rain · Oct–Dec. The south-west monsoon runs parallel to this coast and the Western Ghats block it, so June–September is fairly dry
Kerala — the monsoon’s first landfall · Kerala — Rain · onset ~1 June. The south-west monsoon usually reaches Kerala around 1 June and covers all India by about mid-July
The Ganga plain — rain falls from east to west · Bihar — Rain · ~160 → ~70 cm. The Bay of Bengal branch drops rain as it moves up the plain: Kolkata ~160 cm, Patna ~110, Delhi ~70, west Rajasthan under 25
Punjab — winter rain from western disturbances · Punjab — Rain · Dec–Feb, light. Low-pressure systems from the Mediterranean (western disturbances) bring light winter rain to the NW plains and snow to the Himalaya
Tropical wet evergreen — Silent Valley · Kerala — Forest · rain over 200 cm. Over 200 cm of rain + short dry season → tropical wet evergreen: trees 45–60 m tall, in layers, never bare at once
Tropical wet evergreen — Namdapha, Arunachal · Arunachal Pradesh — Forest · wet evergreen + all zones. Wet evergreen forests also cover much of the North-East
Andaman and Nicobar — evergreen, deciduous and mangrove together · Andaman & Nicobar Islands — Forest · mixed. Heavy rain, hills and a long coast give all three: evergreen, moist deciduous and mangrove (UPSC 2015)
Tropical moist deciduous — sal forests (Simlipal) · Odisha — Forest · rain 100–200 cm. 100–200 cm of rain → tropical moist deciduous: trees shed leaves for 6–8 weeks in dry summer
Tropical moist deciduous — teak (Nilambur) · Kerala — Forest · teak. Teak is the dominant tree of tropical moist deciduous forest (UPSC 2015)
Tropical dry deciduous — central plateau · Madhya Pradesh — Forest · rain 70–100 cm. 70–100 cm of rain → tropical dry deciduous: open forest, leafless for long in summer
Tropical thorn forest — Rajasthan and Gujarat · Rajasthan — Forest · rain under 70 cm. Under 70 cm of rain → thorn forest and scrub: small leaves, thick bark, thorns, long roots to reach water
Tropical thorn forest — western Andhra Pradesh · Andhra Pradesh — Forest · rain-shadow scrub. Rayalaseema (Anantapur) lies in the rain-shadow, so it has open, stunted thorn forest
Himalayan subtropical and temperate broadleaf — oak, rhododendron · Uttarakhand — Forest · 1,000–2,500 m. In mountains, altitude replaces rainfall: every few hundred metres the forest changes
Himalayan temperate coniferous — deodar, fir, spruce · Himachal Pradesh — Forest · 1,500–3,300 m. Cone-bearing, needle-leaved trees that cope with snow
Alpine meadows — Valley of Flowers · Uttarakhand — Forest · above ~3,000–3,600 m. Above the tree line: birch, rhododendron scrub, then alpine meadows (bugyals)
Montane wet temperate — shola forest and grassland · Tamil Nadu — Forest · above ~1,500 m, south. Stunted evergreen forest in hollows, rolling grassland on the slopes — the shola mosaic
Littoral and swamp — Sundarbans mangroves · West Bengal — Forest · tidal. Mangroves grow where rivers meet the sea: salt-tolerant, with breathing roots (pneumatophores)
Mangroves — Bhitarkanika, Odisha · Odisha — Forest · tidal. Brahmani–Baitarani delta; saltwater crocodiles
Mangroves — Pichavaram, Tamil Nadu · Tamil Nadu — Forest · tidal. Pichavaram → Tamil Nadu (UPSC 2002 matching: Achra-Ratnagiri → Maharashtra, Coondapur → Karnataka, Vembanad → Kerala)

Asked in exams

UPSCAreas with over 200 cm rain → Meghalaya, Assam, Nagaland, Arunachal
UPSCRain scanty east of the Western Ghats → it is the lee side (A and R true, R explains A)
UPSCRain on the Tamil Nadu coast in Oct–Nov → retreating south-west monsoon
UPSCMonsoon duration decreases south → north ✓; rain in the northern plains falls east → west ✓
UPSCDecreasing annual rain → Kochi, Kolkata, Patna, Delhi
UPSCMonsoon rain decreases west and north-west in the Ganga plain ✓
UPSCSutlej–Ganga plain gets some winter rain → western depressions
UPSC 1980Silent Valley project was dropped → ecologists warned of environmental imbalance
UPSC 1984Silent Valley project abandoned for → ecological reasons
UPSC 2015Tropical wet evergreen forests occur in → Arunachal and Mizoram (1 and 3 only)
UPSC 2015Climate from tropical to arctic → Namdapha National Park
UPSC 2015Mangrove + evergreen + deciduous together → Andaman and Nicobar Islands
UPSC 2010Largest area among the options → tropical moist deciduous forest
UPSC 2015Teak is a dominant tree in → tropical moist deciduous forest
UPSC 2002Open stunted forests with long roots and thorns → Western Andhra Pradesh
UPSC 2014Seen growing in the Himalaya → oak and rhododendron (not sandalwood)
UPSC 2008Not a Himalayan species → mahogany (juniper, silver fir, spruce are)
UPSC 2011Himalaya rich in species → confluence of biogeographical zones
UPSC 2019National Park completely in the temperate alpine zone → Valley of Flowers
UPSC 2002Match mangroves: Achra-Ratnagiri, Coondapur, Pichavaram, Vembanad → MH, KA, TN, KL

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