If Buddhism was the spiritual sustenance of the ancient Sinhalese civilization, then the wewa (Irrigation Reservoir) was its physical counterpart and, not surprisingly, the two principal symbols of our ancient kingdoms were the dagoba and the wewa.
In fact historically most of our great kings and leaders are remembered for the gifts of the wewas constructed under their patronage or during their reigns. It has even been comparable with the patronage they gave to the spread of Buddhism. It was the wewa that sustained cultivation which produced enough food for everyone and a healthy population. Some kings have been deified for building wewas, and legend has it that the spirits of others still protect the wewas and anicuts they caused to be built. However it is sad that the wewa civilization degenerated with the foreign conquests and abandonment of the ancient kingdoms.
In the mid nineteenth century under the British rule the restoration of the wewas of the northern parts of the island was in charge of Sir Hendry Parker an English engineer, to whose study of the subject is credited a wealth of information regarding the ancient engineering feats that are the wewas.
He says; as one whose duties permitted him to gain an intimate acquaintance with the ancient works
“I have never concealed my admiration of the engineering knowledge of the designers of the great irrigation schemes of Ceylon and the skills with which they constructed the works.”
According to him the origin of the wewa was in the Euphrates civilization from where it came to India and then to Ceylon with the Aryans. This is also in line with the writings of the Mahawamsa.
Yet Parker does not fail to acknowledge that the formation of all reservoirs of a class with embankments much higher than those of simple village tanks was originally due to the constructive genius of the Sinhalese themselves.
He goes on to say; that at an early date they (the Sinhalese) undertook the raising of great earthen embankments, often some miles in length across many suitable valleys thus intercepting the flow of the streams and storing up during the rainy seasons in the reservoirs thus formed immense sheets of water.
The Bisokotuwa was a main feature of this engineering marvel. Parker explains that since about the middle of the 18th century open wells called “valve-towers” when they stand clear of the embankment and “valve-pits” when they are in it have been built at numerous reservoirs in Europe. Their duty is to hold the valves, and the lifting gear for working them, by means of which the outward flow of the water is regulated or totally stopped. Such also was the function of the “bisokotuwa” of the Sinhalese engineers; they were the first inventors of the valve pit more than 2100 years ago.
And that it must have been no easy task to control the outflow of the water at reservoirs which had a depth of 30 or 40 feet, as was the case at several larger works . Yet the similarity of the designs of the bisokotuwas at all periods, that the engineers of the 3rd century BC, if not those of an earlier period, had mastered the problem so successfully indicates that all others were satisfied to copy their designs.
Governor Sir Ward whose intense personal interest in the ancient irrigation system of Ceylon made him declare
“…… there can be no doubt that the run of water is regulated by one of those ancient sluices, placed under the bed of the lake which seemed to have answered so admirably the purpose for which they were constructed, though modern engineers cannot explain their action“.
R.L. Brohier, in his work on the ancient irrigation systems of Ceylon quotes one of the ablest reports on irrigation published by the order of the Ceylon Government in 1855, where Bailey, who was Assistant Government Agent of the district of Badulla says ” it is possible, that in no other part of the world are there to be found within the same space, the remains of so many works for irrigation , which are, at the same time, of such great antiquity, and of such vast magnitude, as in Ceylon. Probably no other country can exhibit works so numerous and at the same time so ancient and extensive, within the same limited area as this island.
Sir Emmerson Tennant contributes to the subject by saying
“the stupendous ruins of the reservoirs are the proudest monuments which remains of the former greatness of the country“
Brohier continues that except for the exaggerated dimensions of Lake Moeris in central Egypt and the mysterious (basin of)Al Aram, the bursting of which embankment devastated the Arabian city of Marieb, no similar constructions formed by any race, whether ancient or modern exceed in colossal magnitude the stupendous tanks in Ceylon. The reservoir of Kohrud at Ispahan the artificial lake Ajmeer, or the tank of Hyder in Mysore can no more be compared in extent or grandeur with Kalawewa or Padivil-colam (Padawiya) than the conduits of Hazekih, the Kanats of the Persians or the subterranean water-courses of Peru can vie with the Ellahara, which probably connected the lake of Minneri and the “sea of Parakrama” with the Ambam-ganga.
According to Brohier yet another branch of engineering which had unquestioningly attained a very high pitch of perfection at the hands of the ancient Sinhalese was that of surveying and leveling. Most of the irrigation schemes are confined to tracts of land which when estimated by the eye appear to all purposes quite flat. Yet we know from such evidence as remains that such channels were traced mile upon mile on gradients that would call into use the most precise instruments of the modern age. And baffling ingenuity which cannot be surpassed by any conceivable means available at the present day traced out the bunds and the contours of the larger tanks. Taking such into consideration it cannot be disputed that under such conditions, to place such magnificent works within the sphere of the possible, a system of measuring heights and distances must have attained a very high level of efficiency.
Therefore he says that it is apparent on the evidence of tradition and fragments of age old inscriptions, that an organization which functioned much on the lines of our modern service for survey existed from earliest times of the Christian era if not even before. And it would be reasonable to assume that the knowledge included some means of ranging outlines and appraising even small differences in elevation.
The Sinhalese should be proud of these achievements. Brohier even quotes an instance where the Sinhalese engineers were commended by other countries for their engineering feats. He says that it is both evident and significant that the Sinhalese made rapid strides, to judge from a note struck by a writer who says “so far had the renown of their excellence in this branch (irrigation) reached, that in the 8th century the king of Kashmir ” Djayapid” sent to Ceylon for engineers to form a lake.