Mahakanadarawa Wewa is a vast reservoir that was constructed in the Anuradhapura kingdom by impounding the Kanadara Oya, the primary tributary of the Malwathu Oya river. The reservoir, also known as Kana Wapi and Kanadiyadora in ancient times, is believed to have been built by King Mahasen (276-303). According to historical records, King Sena II (853-887) constructed a weir at a location called Kattaththa and channeled water through a 12-kilometer canal to the Kanadara Oya, increasing the water supply to Mahakanadarawa Wewa.
The reservoir's embankment spans 2.8 kilometers and covers 34,000 acres (13.76 square kilometers) when full, with a total water holding capacity of 36,250 acre-feet (44,713,717 cubic meters). Regrettably, the Anuradhapura-Trincomalee road cuts across the reservoir, dividing it into two parts.