“ Do not let a single drop of water flow to the sea without being made use of”
EXCELLENCE IN IRRIGATION ENGINEERING
Lessons from the Past irrigation systems those found in Sri Lanka are unique.
The irrigation system in Sri Lanka can be considered as a sustainable soil- water eco system. There are canals that interconnect large and small reservoirs spreading all over the dry zone where this wide network helps to enrich ground water, maintains the eco system and the water table.
Source- amazinglanka. com
“ Do not let a single drop of water flow to the sea without being made use of”
~ King Parakramabahu the First
T he unique irrigation system and the hydro engineering knowledge in the past prove the excellence in irrigation of our nation.
Ancient civilizations were based on river valleys- for example, river Nile in Egypt, Upreties and Tigris rivers( Babylon), Indus and Ganges( India). Even in Sri Lanka, the first kingdom Anuradhapura was based on the valley of Malwathu Oya. Our ancestors built a number of reservoirs, anicuts, and canals in the dry zone establishing their civilizations. Engineering skills in such marvels still never fail to amaze today’ s engineers.
Source- amazinglanka. com
The concept“ Wewai dagebai-gamai pansalai”( the tank, village and the temple) implies that the hydro engineer had quite a responsible role in the ancient society. Eventhough Sri Lankan culture was influenced largely by parallel civilizations in India, the advance
In the late 1970s, when Maduru Oya reservoir was constructed under Mahaweli Project, the old anicut and the sluice which dates back to 5th or 6th century A. D. were found in exactly the same position. The same was observed in Urithissa Tank( Ridiyagama) which very well proves the excellence of ancient engineers. Kala Wewa spillway( the tank), Minipe Anicut are also some examples of the skillful engineering work of our ancestors.
Kirindi Oya dam is another ancient engineering product, built at an oblique angle of nearly 45 degrees, instead of going across the shortest possible route. It is found that this design increased the discharging power and the ability to withstand shocks.
THE SLUICE AND SLUICE GATES Sluice and sluice gates are the most important parts of an irrigation tank. It’ s purpose is to control the outflow of water without damaging the dam.( It’ s found that the ancient engineers used a‘ Keta Sorowwa’( Removable part of a pipe in smaller tanks). The sluice was connected to a number of keta, which were kept on top of another, such that the water head of the sluice inlet could be controlled by removing the‘ keta’. Hence, the flow rate through the sluice could be controlled to the desired level.
However, when it comes to larger tanks like Parakramasamudraya, Kala Wewa etc. keta sorowwa could not be used, as the water head was much greater. As a solution for this problem, ancient engineers used“ bisokotuwa”. It is one of the greatest engineering techniques in the history of irrigation. It is square in shape, with a length of 8-12ft and a width of 8-10ft( placed inside the dam). When the inlet gates are opened, water flows into the bisokotuwa through a conduit. When water reaches the head to a safer level, the outlet gate opens and the water flows through the sluice smoothly.
10 University of Peradeniya Gauge Magazine