Pioneers of Ancient Irrigation
Some irrigation systems in Sri Lanka have been found to be built dating back to King Abhaya (474-453 B.C). The Sinhalese where the first in the ancient world to build complex, complete man-made reservoirs and underground canals. They also invented the Bisokotuwa (the valve-pit).
Yoda Ela canal (built by King Dathusena in fifth century AD) spans 87 km and has a gradient of approximately 10-20 cm per kilometer! Historians are amazed that the Ancient Sinhalese managed to maintain such a consistent slope over such a long distance. Makes you wonder what ancient measuring methods could have been utilized to achieve such a feat.
Through the next 1500 years, over 30000 ancient reservoirs where built especially when The Great King Parakramabahu, (1153–1186 AD) declared “Let not even a drop of rain water go to the sea without benefiting man”.
My personal experience: On my holiday to Sri Lanka I went to see the beautiful Maduru Oya (Victoria damn built in the 1980’s). At the site, there was a sign that truly amazed me. It said that during the construction for a sluice for the Victoria damn, excavators happened to uncover an ancient sluice built thousands of years ago. This ancient sluice happened to be built parallel to the proposed sluice for the Victoria damn. This highlights the truly superior methods of Ancient Sinhalese hydro-engineering which is still on par with modern day hydro-engineering methods.