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A cascade system is a connected series of tanks organized within a micro-catchment of the dry zone in Sri Lanka. The tanks are used to store water from a seasonal stream. The stored water is conveyed to other tanks downstream and used for a variety of purposes. Irrigation tanks are often not isolated tanks but are part of a larger interconnected system of tanks called a ‘tank cascade system’. It has connected with series of tanks organized within a micro-catchments.   A ‘cascade system’ is the traditional unit used in the management of tanks. From ancient times it is referred to as ‘Ellangawa’. The term is made up of the Sinhalese words ‘ ellan ’, meaning hanging and ‘ gawa ’, meaning one after the other. The image on the left shows the organization of tanks and their connectivity within a typical tank cascade system. The image below shows the micro-catchment of a typical village tank, which is usually the main tank of a cascade system. Different river basins have different numbers o