Ruwanthika Hewage - Google
A twin reservoir complex built in the 5th-century by King Dathusena, the Kalawewa can hold up to 123 million cubic meters of water. The stone made spillway “Biso Kotuwa” and the long canal called “Jaya Ganga” or “Yoda Ela” with a perfect slope of six inches per mile demonstrates the hydro-logical engineering marvels of ancient Sri Lankans,
King Dathusena was known for his contributions towards the development of irrigation systems in Sri Lanka. In the mid 5th century Anuradhapura was invaded by South Indian invaders. Dathusena fought against and defeated the invaders. He wanted to restructure and develop the country's irrigation systems and built the Kala Wewa, following the completion of Kala Wewa he built another tank called Balalu wewa and connected the two to form the biggest tank in Sri Lanka.
Chronicles suggest that Dathusena’s son prince Kashyapa was led to believe that Dathusena had hidden treasures, Kashyapa went to his father and asked where these were. King Dathusena accompanied Kashyapa to the Kala Wewa and took a handful of water and said this is the greatest treasure he had. Having failed to understand what his father meant Kashyapa killed his father by walling him up alive in the bund of Kalawewa.