Archaeological evidence shows that during the early stages of irrigation activity in Sri Lanka, its ancient dwellers depended more or less upon 'shifting cultivation'. That is, they moved from place to place in the jungle until they chanced upon a water source, selected a certain area of forest nearby, cleared it, burned the fallen trees, settled themselves in small houses and cultivated the same plot of land repeatedly throughout the coming years until the soil gradually grew less fertile. When harvest diminished it was their signal to move out to another part of the wild and restart the process. The previous settlement was abandoned to the forest.
Surprisingly, this method of shifting cultivation is practiced even today, although in micro scale, in certain rural villages of the island.
However, at some point of history, the primeval farmers grew tired of this 'shifting cultivation' that lacked both stability and reliability. Instead they were much more interested on developing large scale irrigation that would help them to cultivate extensive swathes of land which would ensure a constant supply of food and water throughout their lifetime.
One challenge they faced from the very beginning on this regard was to preserve water in drought. Second one was to control it during flooding. If not properly handled, in either situation, their crops were destroyed. Even now, the dual challenges remain unchanged for a majority of people living in the Dry Zone of Sri Lanka.
From March to September, when North East Monsoon winds are inactive, they are short of water. From October to February, when North East Monsoons awaken, they face devastating floods.
One solution of the early farmers to overcome this situation was to block a stream by building a dam at a strategic point during rainy season and let it pool, burgeon and expand in to a lake. If the dam could not hold the pressure, the excess water was released by spillways and if that is not enough, through sluice gates of the dam. The surplus was directed to another lake downstream. If the second lake also fails to handle the rising waters, then its gates are also opened to feed yet a third lake along the line. This process was repeated until the expected equilibrium was reached. When rain stopped and dry spell came, the dwellers had nothing to worry. All their lakes were brimming with water captured during the previous rainy season. They were more than ready for the drought.
This was the initial stages of the Ellanga System / Cascaded Tank-Village System which later developed into a myriad of lakes, canals, spillways and cultivable land that provided food and water for the whole population of pre-colonial kingdoms, during their entire lifespan.
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Ellanga System / Cascaded Tank-Village SystemNon-Fiction
In Rome, on 19th April 2018, Food and Agriculture Organization (FAO) of the United Nations designated Sri Lanka's ancient yet still functional irrigation mechanism known as Ellanga System (to be more analytical and technical; Cascaded Tank-Village S...