Sri Lanka commitee of the
International Network for Water and Ecosystems in Paddy Fields

Water Resources of Sri Lanka

Over a surface area of 65,600 km2, 19.5 million people live in the country. Water bodies, a considerable portion of which are man-made, cover about 4 percent of the land. The terrain of the island is mostly made up of coastal plains, with mountains rising only in the south central part.


Sri Lanka is a classic example of the "hydraulic civilization" which had developed in the ancient period. With the immigration of Aryans from Eastern India to Lanka in 543 BC, cultivation of rice developed into a grand scale in the island. As the new essentially agricultural Aryan civilization flourished, increasingly ambitious projects of irrigation were launched at a pace with a view to harness the monsoon rains. It can be safely deduced that the first great reservoirs ever in the world were built in Sri Lanka. Since the great lakes of Egypt, being merely natural hollows into which streams were turned do not fall into the category of man-made rainwater reservoirs as those of in Sri Lanka.

The rainwater reservoirs developed in the ancient kingdom of Anuradhapura (437 BC-845 AD) & Polonnaruwa (846 AD-1302 AD), Dry Zone of central lowlands resulted in two season of farming while the Wet Zone remained sparsely populated and covered by thick forests. Today around 12,000 ancient small dams & nearly 320 ancient large dams together with thousands of man-made lakes dot the lowlands, with over 10,000 reservoirs in the Northern Province alone. Today Ancient Sinhalese irrigation supplemented by Modern Irrigation Projects continues to provide the self-sufficiency in cultivation of rice, which is the major food of the Sri Lankans.

The great royal tank builders of ancient Lanka

  • King Abhaya (474-453 BC) built the first rainwater reservoir of the island
  • King Pandukabhaya (437-366 BC): built Abhayawewa (Basawakkulama wewa) rainwater reservoir in Anuradhapura
  • King Vasaba (65-108 AD): built a dozen irrigation canals & eleven tanks, the largest with a circumference of three kilometers.
  • King Mahasena (276-303 AD): built the vast Minneriya tank & fifteen other reservoirs
  • King Dhatusena (461-478 AD): built the vast Kala Wewa rainwater reservoir & remarkable 90km long Jaya Ganga (also called Yoda Ela) canal with a subtle gradient of 1 ft per mile
  • King Moggalana (497-514 AD): built the Padviya this became the largest tank at the time. Today following restoration it is slightly
  • smaller than Kalawewa & Minneriya weva.
  • King Aggabodhi the third (623-639 AD):built the Giritale tank & several other tanks
  • King Dappula the second (807-811 AD): built the Panduwewa (Pandu water reservoir)
  • King Parakrambahu the great (1164-1196 AD) The royal master builder of tanks
During the reign of the great king, Lanka became to be known as the Granary of the Orient. King Parakramabahu the great built the restoration of 165 dams, 3910 canals, 163 major tanks and 2376 minor tanks, all in a reign of 33 years, achieving supreme developments in irrigation and agriculture of the Sinhalese civilization during its 2550 year long history. Decline of the ancient Hydraulic civilization of Sri Lanka The fall of the ancient hydraulic civilization of Sri Lanka in the 13th century was due to sudden Natural Cataclysmic change of the river course of the Mahaweli Ganga & was not due to foreign invasions as historians would want us to believe. The scientific evidence is clearly seen in the aerial photographs of the old course of the Mahaweli Ganga & its new river courses. The ancient Mahaweli with its ancient charities which were beside the old river like a string of pearls now lay stranded beside it. While the present river flows elsewhere with no charities beside it which event took place in circa 1220 AD. This sudden geological cataclysm that changed the river course that sustained our ancient hydraulic civilization, led to disease & famine. This resulted in the major part of the population to abandon these areas & move to the Wet & Intermediate Zones where the king also established himself at Dambadeniya, Kurunagala, Gampola, Kotte & Kandy.

Further Decline of Ancient irrigation schemes during British Colonialism (1815-1948) in Ceylon

During the early period of British rule the colonial administration was pre-occupied with military & political consolidation, & thereafter, with capitalist enterprise in plantation exploiting the riches of the island supplanted cultivation of rice with cash crops, first coffee & then Tea & Rubber. With no interest taken & no support extended to the farmers on irrigation of paddy fields, the tanks gradually fell into disrepair, turning much of the countryside into malarial swampland. A modern historian calls this a "regrettable but understandable situation, given the fact that the higher bureaucracy itself had been so deeply involved in plantation agriculture

Rehabilitation of ancient rainwater reservoirs

The dire situation of the island resulted in a national independence movement taking root over the issues of land, irrigation & cultivation. Having realized the gravity of the situation, during the second half of the 19th century & first half of the 20th century, the British colonialists launched on a project of restoration of ancient rainwater reservoirs. Restoration of the major Kala Wewa rainwater reservoir with a capacity of nearly 145 million cbm was carried about during 1885 to 1887. Following the independence from the British in 1948, the rehabilitation of major ancient irrigation works has been accelerated by the national leaders of the independent Ceylon.

"Many are the instances where the modern engineer has frequently found himself anticipated by an unnamed predecessor" Ceylonese historian R. L Brohier

Largest ancient rainwater reservoirs

The Sea of Parakrama (2100 ha), Kaudulla (2537 ha), Minneriya (2550 ha), Huruluwewa (2125 ha), Kala Wewa rainwater reservoir (2583 ha), Mahakanadarawa (1457 ha), Nachchaduwa (1785 ha), Padaviya (2357 ha), Rajangana (1600 ha) Large and medium reservoirs 73 major irrigation reservoirs (ancient) covering an area of 70850 ha 160 Medium scale reservoirs (ancient) covering an area of 17004 ha 10000 minor irrigation reservoirs (ancient) covering an area of 39271 ha Floodplain lakes covering an area of 4049 ha Ancient irrigation Vs Modern irrigation
Gal Oya Scheme In 1952, modern Gal Oya Scheme testified to the brilliance of the ancient masterminds of irrigation engineering in Lanka: the discovery of remnants dated back to 1500 years of a dam site and two sluices almost exactly at the locations determined for the new reservoir by the engineers at the Gal Oya project. In order to preserve the excavated ruins of the dams & sluice gates, the priceless archeological findings, the government decided to move the new dam site to another location. Maduru - Oya reservoir In 1978 when modern engineers cleared the jungle to pave the way for the modern Maduru-Oya reservoir they stumbled on an ancient breached earth dam at the very spot where engineering experts had decided to straddle the river. This dam a little over 23 meters high has been dated to be over 2000 years old & indicates the existence of a vast reservoir before its breach.