Physical Geography of Sri Lanka

Physical Geography of Sri Lanka

Location separate Island from the Indian subcontinent, encircled by the Indian Ocean strategic location near major Indian Ocean sea routes located 5 0.5— 90.5 North Latitude and 790.52 - 81 0.52 Eastern Longitudes 29 Kilometers off from the southeastern coast of India, but connected to India till about 5000 BC. 

Bay of Bengal to the east and Gulf of Mannar and Palk Straits on west in Paleolithic period Sri Lanka and India was connected by means of a land bridge even today one can see 1 8 Islands (limestone shoals) from Talai Mannar to Rameswaran in India 8 of these belong to Sri Lanka and the rest to India after submerging the bridge this chain of mounds, remain above the sea level according to Ramayana, the Hindu Epic, this is the remnant of the brick that was built by Hanuman ji total extent of Sri Lanka is 65,610 square km and inland water covers about 2905 square km Tear-drop shaped island extending from south tip of India but some say it is like a pendent hanging from India the breadth of the broadest part (Colombo to mount Sangamam) is 227 km.

length from north to south (Point Pedro, the northern point to Point Dondra) is 434 km mostly low lands around the central hills and these hills are located in south central interior three zones could be identified by elevation; i.e. coastal plains, intermediate zone & central hills 

Coastal Plains 

                                                                                                                        Right round the island with altitude lower than 30m is identified as coastal plains ringed with palm trees; i.e. north and east Palmyra trees and the rest mostly coconut trees most of the area is covered with sandy beaches and coastal lagoons for fishing and salt industry limestone beds exposed to waves as low-lying cliffs in extreme north, Jaffna Peninsula there had been so many ancient ports round the island and some of them are still functioning natural harbor at Trincomalee on north east coast is a deep-water port earlier this was known as Gokanna, a major port on east coast facing Bay of Bengal smaller rock harbor at Galle on southwestern coast was important for ancient trade routes Mantai is another ancient port located near Mannar Island, 64 km south of Jaffna this was a large trade emporium at a critical location for east-west trade because of this port, Sri Lanka was well known to Greeks and called Taprobane the prehistoric Thiruketisvaram Hindu Temple is situated in Mannar District 

Intermediate Zone 

These are the higher level plains between 30m and 200 m above sea level  soils of this area change from sandy and saline to fertile loams (a rich soil containing clay, sand and decayed vegetable matter) 

Southwest, ridges and valleys rise gradually, merge with Central Highlands.

transition from plain to Central Highlands ends abruptly in southeast part of the Island plain dissected by long, narrow ridges of granite from Central Highlands this intermediate Zone is sub-divided into three parts 

I. Southwestern Section of intermediate Zone is known as Dakkhinadesa in ancient times series of ridges and valleys could be seen from Deduru Oya to Hambantota in this region ancient landscape much eroded by heavy rains commercial Capital of Sri Lanka Colombo also located in this region 

Sabaragamuwa Province where the location of Gem-bearing gravel beds too, included in this Zone  Ratnapura, Kelaniya, Kotte-Jayawardenapura, Panadura, Beruwala are some prominent cities 

2.       Southeastern section of intermediate Zone is known as Rohana or Ruhunu Rata,  also known as Atadahas Rata and Dolosdahas Rata mountains of interior rise sharply from this Zone separated by River Mahaweli and River Kaluganga in ancient times this zone extends as far as Mahaweli Ganga and Trincomalee Bay now sparse population but archaeological evidence indicates as once populous 

3.       Northern section of intermediate Zone is known as Rajarata or king's country located between Mahaweli Ganga on east and Deduru Oya on west very flat plain portion of land tapering towards Jaffna Peninsula peninsula area oflimestone and very different from remainder 

Anuradhapura, Polonnaruwa and Yapahuva are prominent ancient cities.

Central Highlands, the Hill country

Remarkably different from the other parts of country occupies about one-fifth of territory of island in south-central portion durutalagala in Nuwara Eliya is the highest point of the island and the height is 2524m from Mean Sea Level.

The other highest mountains are:

Kirigalpottha in Nuwara Eliya 2395m

Mt. Totapola in Nuwara Eliya 2357m 

Adam's peak in Nuwara Eliya 2238m 

Hatton Plateau is one of the series of upland plains hill country is remarkable as it remained independent of foreign rule for the longest period Kandy, Gampola, Kurunegala, Dambadeniya are some of the important capitals 

Climate

Equatorial situation and tropical condition of the island is influenced by elevation above sea level rainfall too, uneven throughout the year annual rainfall varies from 1200-1900mm in the Dry zone mountain and southwestern part of the country is known as the wet zone wet zone receives 2500mm annual rainfall southeast, east, and northern parts of country comprise the dry zone northwest and southeast coasts are arid zones which receive least rain i.e. 600-1200mm humidity typically higher in southwest and mountainous areas.

Monsoons

normally three monsoons are experienced every year southwest monsoon from May to September with heavy rains northeast monsoon from November to March both monsoons precipitate the central hills convectional rains to the whole island during April and October as inter-monsoon.

Temperature

Temperature in Colombo and suburbs varies from 25 0C-28 0C temperature in Central hills and other higher elevations are 140C-160C as 100 meters rise-up the altitude, one Centigrade of temperature goes down average yearly temperature for the country from 260C-28 0C December and January are the coolest months and March to May, the hottest months normally day and night temperature vary from 40-70 C 

Vegetation

Typical ground cover, scrub forests could be seen in general, mixed with tough bushes and cactus's in the driest area plants grow fast from November-February as the rain fall is heavy, but stop growing during hot season, March-August forests cover almost Whole Island but recently depleted to 20% 

Mangroves

Goes under water when water level is high one could see them in Batticoloa, Negombo, Puttalam, Bentota, Gintota, Nagarkoil, Kumana etc. structure for adaptation: - Prop roots and breathing roots high bio-diversity 

Forest communities

wet Zone rainfall over 2500mm and no dry period, temperature about 27oc

Tropical ever green forest

(Rain forests) altitude up to 1000 m high forest has three layers i.e. Emergent up to 45m, Canopy between 25-30m  Sub-canopy between I O- 15m 

e.g.

Sinharaja (World Heritage), Gilimale, Kan Eliya, and Kottawa etc. 

Sinharaja: 143 tree species and 60% of them are endemic many mosses, creepers, lianas, and epiphytes are freely available as strictly reserved forest this has escaped the activities of man 

Sub-Tropical Mountain Forests

 located between 1000-1500m of altitudes normally, low temperature and the coldest months go below 160 C rainfall high, but shorter trees mostly, and canopy level lower 10-15m twisted and gnarled trees due to cold wind tree trunks covered with mosses, lichens, fungus, algae, and epiphytes etc. 

mid country forests is called Sub-Mountain Tropical Wet Evergreen Forests (intermediate forests) 

Dry zone

Two third of the country gets around 1800mm, annual average rainfall pronounced Dry season during south-west monsoon, some trees deciduous, others evergreen most widespread canopy level 20m, sometimes emergent 3m over canopy drier areas are Puttalam, Mannar, Hambantota etc.  thorny species and shrub species are also common to these areas forests are untidy, messy and tangled

Intermediate Zone 

Intermediate Evergreen forests and Tropical Semi-evergreen forests could be seen in Kurunegala and Moneragala respectively Wet zone species towards the wet zone and dry zone species towards the dry zone 

Wet Zone

Grasslands between 460-1500m altitudes tall bushy grass 'Cymbopogon confertiorous' (Maana) common in dry patana Wet patana in Central mountain ridges such as Horton, Moon, and elk Plains also called wet black patana scattered trees, mainly 'Rhododendron arboreum' (Maha rath mal) which is endemic to Sri Lanka Dry Zone grasslands could be found in Flood Plains, Mahaweli, Somawathie National park etc. 'Villu', moist grasslands common to these parts 

Planted Forests 

           Pinus (wet), Eucalyptus (wet & dry) Tecona or Teak, Mahogany, Ipil Ipil, Casurina and Jak are common trees in planted forests 

Native or indigenous plants 

these plants have come to Sri Lanka without the intervention of man 

90% of them are land or terrestrial 10%/maritime and fresh water these plants are only found in Si Lanka

Endemic 

830 species are endemic out of 3368 plants in the Island (25%) this is a very high percentage 

Sri Lanka three times smaller than England but has three times more endemic species most endemic plants are in the wet zone which has come to 60% 

Infrodenceal Plants or introduced plants brought by man intentionally or unintentionally with grains, fertilizer, packing materials etc.  

most of the weeds have come to Sri Lanka in this manner 

Naturalized Plants, when introduced they adapt themselves and Sri Lanka has about 200 of! them . Lantana camara (Gandapana), Anacardium occidentale (Cashew nut), Mimosa pudica (Nidikumba) 

Eg

           Natural water sources

most rivers are short as the country is a small Island only 16 rivers are longer than 100km 

12 rivers carrying about 75% of Mean River discharge in the entire country longest rivers are Mahaweli Ganga, 335km and the next longest is Malwathu Oya 170km Mahaweli Ganga flows from Horton Plains to northeast coast at Trincomalee Malwathu Oya from Ritigala to Manthai Kala Oya flows from interior to northwest coast at Dutch Bay, north of Puttalam lagoon Deduru Oya flows from interior to west coast at Chlaw Maha Oya flows from interior to west coast at Kocchikade, north of Negombo Kelani Ganga flows from interior to west coast at immediately north of Colombo Kalu Ganga flows from interior to west coast at Kalutara south Bentota Ganga flows from interior to west coast at Bentota Gin Ganga flows from interior to southwest coast at Gintota, north of Galle Polwatte Ganga flows from interior to south coast atWeligama and Weligama Bay Nilwala Ganga flows from interior to south coast at Matara Walawe Ganga flows from interior to south coast at Ambalantota rivers radiate from Central Highlands, flow in radial patter toward sea Highlands, river courses frequently broken by terrain once at the plain, slow down and waters meander across flood plains and deltas upper reaches or rivers are wild, impossible to navigate lower reaches are prone to seasonal flooding 

Man-made reservoirs for irrigation 

Human intervention has altered flows of some rivers and created a hydraulic management system Sri Lanka home is to one of early hydraulic cultures in the world rivers in north, north central, east and southeast feed artificial reservoirs for irrigation from ancient times, function to provide storage for water during dry season