…….At first, only the simplest works of the smaller class, with very low embankments, would be undertaken but when a better knowledge of the art of raising such banks of earth to hold back greater depths of water was acquired, schemes of a more comprehensive character would be attempted, until at last no reservoir was looked upon as too great to be constructed, and the lengths of the embankments extended for any distance up to a maximum of nine miles, while their heights in a few instances rose to more than fifty feet…………. Parker, an Irrigation Engineer who was in charge of restoring many ancient irrigation reservoirs in late 1800’s, in his book ‘Ancient Ceylon’ Europeans stared using the valve pits in their reservoirs only in the mid 18th century, 2100 years later according to H. The breakthrough which made the Sri Lankan Irrigation Engineers build such massive reservoirs was invention of the “Biso Kotuwa” of valve pit as early as 3rd century BC which could easily regulate the out flow extremely large water bodies. From that day onward Sri Lankan tank builders developed a remarkable expertise on controlling large bodies of water which allowed them to built massive reservoirs which no other civilisation ever could have dreamt of. The first large reservoir to be built in recorded history is Abaya Wewa in 3rd century BC. kilometres (where almost all the tanks are located), is almost equivalent to one reservoir for each sq. This compared to the Sri Lankan dry zone land area of about 40,000 sq.
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There about 30,000 reservoirs in Sri Lanka of which the majority was built form 3rd century BC to 12th century. Irrigation systems of ancient Sri Lanka consist of a large number of village reservoirs to gigantic reservoirs and a intrinsic network of water canals connecting these tanks while supplying water to farming land.