A Scheme That Holds Water: An Irrigation System That Goes Back to Ancient Times

A Scheme That Holds Water: An Irrigation System that Goes Back to Ancient Times

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By Mr Ghaz, March 4, 2010

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A Scheme That Holds Water: An Irrigation System that Goes Back to Ancient Times

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Before Dawn one morning in 1848 a British writer and traveler, Sir James Emerson Tennent, set out by torchlight through the northern forests of Ceylon on an arduous journey. He had heard that in the dense jungle lay one of the engineering wonders of the ancient world.

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The wilderness was difficult to penetrate. Since the path was narrow and choked with thorn trees and luxuriant climbing plats, for most of the 10-mile trek the members of Tennent’s party were forced to lead their horses on foot.

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Finally, Sir James reached his destination, There, stretching before him, were the remains of a huge reservoir. Its scale had Sir James searching for superlatives, for he knew that this astonishing feat of engineering, known as the Padawiya Tank, was more than 1,500 years old. The team spent two hours on horseback crossing the vast expanse from the point at which they entered the bed of the reservoir to its dam, or bund.

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“The extreme breadth of the enclosed space,” wrote Sir James, “may be 12 or 14 miles, narrowing to 11 at the spot where the retaining bund has been constructed across the valley; and when this enormous embankment was in effectual repair, and the reservoir filled by the rains, the water must have been thrown back along the basin of the valley for at least 15 miles. The dam itself,” he added, “is a prodigious work, nearly 11 miles in length, 30 feet broad at the top, about 200 at the base, upwards of 70 high, and faced throughout its whole extent by layers of squared stone.”

Ahead of Their Time

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Padawiya is known to be just one of thousands of reservoirs and elaborate waterworks built from the 1st to the 12th centuries A.D. on the island today called Sri Lanka. The waterworks range from the ponds designed to serve individual villages to vast man-made lakes. The largest, the 6,000-acre Parak-rama Sea, was enclosed by a barrier almost nine miles long and 40 feet high.

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Sri Lanka’s climate made the construction of an elaborate irrigation system necessary. For much of the year up two-thirds of the island is threatened by drought and must have water if rice is to grow. The ancient Sinhalese kings recognized the need for an irrigation system and ordered the building of tanks, dams, and canals to trap the monsoon rains. Said one king after surveying his kingdom: “Truly in such a country, not even a little water that comes from the rain must flow into the ocean without being made useful to man.”

Mass Construction

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The historians of ancient Sri Lanka (Taprobane) maintained careful records of the achievements of each ruler. Vasabha (65-109) is credited with the construction of 12 tanks and 12 canals; Mahasena (274-302) commissioned 16 tanks, including Minneri, which covered 4,670 acres. In the reign of King Dhatusena (460-478) a canal 40 feet wide and 54 miles long provided water for the capital city of Anuradhapura in the north. Most energetic of all, however, was Parakrama Bahu I. From 1153 to 1186 he was responsible for the construction of 770 tanks and 534 canals, and for the successful repair of 2,300 tanks and 3,621 canals.

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The tanks and canals were a spectacular success. Crops flourished, and the money they brought paid for great temples, pleasure gardens were fountains played, and cities with palaces as high as nine stories. Between harvests, the people worked on the vast construction projects; their labor was a form of rajakayira, a tribute paid to the king.

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Although wars, the encroaching jungle, and the deaths of the great engineer-kings brought ruin to many of the tanks, the tradition of great irrigation projects still survives in Sri Lanka. Many of the tanks rediscovered by 19th century explorers have been restored, and vast new undertakings, such as the Mahaweli Diversion Scheme, are under way, bringing water to hundreds of thousands of acres of arid land and doubling the country’s supply of electric power.

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With the aid of bulldozers and computers, the comprehensive irrigation system of Sri Lanka, initiated by the kings of ancient times, continues.