The Vewa and Ancient Tradition
Ancient Sri Lanka boasts a distinguished hydraulic civilization. The technology used to construct the irrigation system of Sri Lanka is unmatched, and has long confounded and fascinated acclaimed irrigation engineers such as Henry Parker (a British hydraulic engineer who served in the Department of Irrigation during the 1880s).
The Vewa (irrigation tank) and the lives of ancient villagers were and still are intrinsically interconnected. If there wasn’t a Vewa to be seen in a particular area there was neither a paddy field nor a village in the vicinity. The Vewa, aside from fulfilling water and irrigation requirements of the Sri Lankan people, was also the quintessence of the grand and extensive cultural ethos of ancient villagers. The use of the irrigation tanks and the water and agricultural traditions associated with them has been passed down through generations and are still present today.
The importance of these tanks to the people of the nation can also be derived from the fact that a village within the vicinity of a particular Vewa was, more often than not, named after it - for example, Siyambala Vewa, Athavatuna Vewa, etc. The Vewa was a common asset of the villagers and as such every villager was responsible for its maintenance and care.
Large Scale Vewas
Many of the Sri Lanka’s kings insisted in constructing irrigation tanks in an effort to generate wealth for the country and improve the lives of its people. The capacity and prominence of ancient kings was assessed by the number of irrigation tanks he had constructed.
Construction of irrigation tanks requires a large labor force as well as irrigation engineers. The labor force was provided food for the period of their employment; thus, the economic and political stability of the country often played a significant role in deciding when a large scale irrigation tank can be constructed. Administration of the Vewa was assigned to a person called the ‘Vew Vidane’.
Tank Bund (Vew Bamma):The Vew Bamma is made of soil that is pressed and pounded to ensure strength. In the past, animals such as oxen and goat were driven over heaps of soil several times to compact it. It holds water inside the tank.
Sluice Gates (Sorowwa): Sluice gates are constructed to release water into paddy fields for irrigation. There are two parts to a sluice gate called the Mada Sorowwa and the Goda Sorowwa. The Mada Sorowwa is located at the bottom of the tank and expels the mud accumulated there. The Goda Sorowwa releases water into paddy fields. Sluice gates can be divided into two categories based on the technology used. The technology used in the construction of valve pit/tower (Bisokotuwa) in large scale irrigation tanks is particularly applauded. The Bisokotuwa takes the shape of a well and is made of granite. It follows a sophisticated water regulating system called ‘Mohola’ which releases the right amount of water at the right time. A ‘log sluice gate’ is set up in small scale Vewas; cylindrical logs are arranged on top of each other. These Vewas can be emptied completely by taking off the logs.
Surplus Weir (Pitavana): Pitavana is constructed to protect the tank bund from damage during heavy rainfall by discharging excess water. The excess water travels through a small stream called ‘Van ela’. Water discharged from the surplus weir does not cause any harm to paddy fields.
Stone Liner (Ralapanava): This is a granite stone liner constructed on the inside of the tank bund to prevent it from being eroded by the water current.
Silt and debris are retained at the Vew Thavalla and prevents them from flowing into the water within the irrigation tank. Many trees, creepers and vines can be found in the Vew Thavalla which helps retain the silt and debris. For this reason, clearing the Vew Thavalla was restricted in ancient times.
The Diyakata Pahana measured water level of the Vewa; if the level was too high, the sluice gates were opened releasing excess and if the level was too low releasing water into paddy fields was done more restrictively and meticulously.
Other uses of Vewas
Apart from irrigation, tanks were also used for many other purposes such as fishing, bathing, washing clothes, and bathing animals.
Different areas of the tank were used for different purposes; ‘Diya Mankada’ is the area used to obtain drinking water; the water in this part of the Vewa is therefore cleaner than any other part. The ‘Nana Mankada’ is reserved for bathing and is located at a distance from the Diya Mankada and always down from it so the water from the bathing area does not reach the drinking area. The area allocated for bathing is shallow and does not get muddy even after extensive use. ‘Rada Mankada’ is the portion dedicated to washing clothes, and the ‘Boradiya Mankada; is the place used to bathe working animals such as oxen and Buffalos.
Refurbishment of the Vewa
Refurbishment is done during the dry season when the water of the tank has dried up. An auspicious day is decided by the Vew Vidane to commence refurbishment. Each part of the Vewa is apportioned to a particular villager and he is responsible for cleaning and protecting it from damage.