Kala Wewa, which also in nearby vicinity built by the King Datusena in 307 B.C, is a twin reservoir complex (Kala Wewa & Balalu Wewa) which has a capacity of 123 million cubic meters together making the biggest tank in Sri Lanka. Water of the tank was transferred to the Thisa Wewa in Anuradhapura by an ancient 86.9 km long canal called Yodha Ela which has a fine slope of one foot per mile While supplying water also for the small tanks in rural areas on the way.
Being one of main storages in the Mahaweli Irrigation Scheme since 1976, the tank serves to the population in the North Central Sri Lanka. It is used for fresh water fishing and the flora, specially the grasses in its valley, for the herds of cattle in the area.
