The ancient civilization of Sri Lanka emerged and flourished in the islands dry zone. The extensive northern plain region and the smaller plain in the southeast that together encompass more than two-thirds of the island early settlements sprang up on river banks in this region. The pioneers subsisted on rice a crop that depended on the vagaries of the monsoons.
Settlements quickly spread across the plains prompting an urgent need for a means of coping with the geological and geographical peculiarities of the dry zone and its frequent droughts. Thus, Sri Lanka became one of the greatest irrigation civilisations of the ancient world
Geniuses of Irrigation
Large-scale irrigation networks began crisscrossing the parched landscape which started as early as the 1st century A.D. Sri Lanka’s engineers utilized the waters of the Mahaweli river and other rivers that flowed down to the plains from the mountains of the wet zone. The construction of their canals and channels exhibited an amazing in depth knowledge of trigonometry; and the design of their reservoirs or wewas revealed a thorough grasp of hydraulic principles Their dams had broad bases able to withstand very heavy pressures outlets for the discharge of water were installed at suitable points in the embankment. The method of regulating the flow of water from these tanks, as the artificial lake reservoirs are called today, was ingenious. By the 3rd century B.C., Sri Lankan engineers had invented the BISOKOTUWA (valve pit), the prototype of sluices regulating the flow of water from contemporary reservoirs.
The increasing sophistication of irrigation technologies enabled Sri Lanka’s early settlers to extend the water networks throughout the dry zone by the 6th century A.D engineering milestones included the Kantalai tank built by King Mahasena (274-302). It covered 4,560 acres was fed by a canal 25 miles long,and was contained by a dam 50 feet high. Even more superior in technology was the Kalawewa constructed by King Dhatusena (460-478). It encompassed seven square miles and had a dam 31/2 miles long and 36 to 58 feet high with a Spill of hammered granite. A canal 54 miles long and 40 feet wide linked it to the city of Anuradhapura and played an integral role in the development of that ancient capital. The first 17 miles of this canal had a gradient of only six inches slope per mile.
Subsequent centuries saw even more remarkable developments in the irrigation of Sri Lanka. By the end of the 8th century, irrigation systems enabled the islanders to open extensive tracts of land to cultivation.
Cores of Civilsation
Against this backdrop of technological and agricultural growth two important cores of Sinhalese civilization rose in the irrigated plains of the dry zone. Anuradhapura,in the centre of the northern plain, and Polonnaruwa, futher to the southeast near the Mahaweli in time and in succession become the capital cities of the whole Sinhalese kingdom.
Polonnaruwa boasted one of the largest and most spectacular of Sri Lanka’s ancient tanks, the Parakrama Samudra, the sea of Parakrama. It was buit by Parakramabahu 1 (1153-1186) one of the greatest of the Sinhalese rulers. The bund of the Parakrama samudra was nearly nine miles long and rose to an average height of 40 feet. Nothing of this scale was built again until Sri Lanka regained her independence from the British in 1948.
The third core of Sinhalese civilisation, Ruhuna, was located near modern Magampattu, in the far southeast of the dry zone where the climate is even more severe, and rainfall less reliable, than in the kingdoms to the north. The region was settled by the ancient Sinhalese almost as early as Anuradhapura and a well developed irrigation system was established there at least 2,000 years ago. Ruhuna periodically asserted its independence from the other two centres of Sinhalese power and served as a refuge for their defeated kings or rival claimants to those thrones. However, it was frequently controlled from Anuradhapura, and seems never to have rivalled those cities in economic power or population resources.
There is the Yoda ela that took water from the Kala Oya to Anuradhapura by a canal having a gradient of half a foot to the mile which even today with modern technology is difficult to achieve.
Water
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