Mahakanadarawa Wewa is a large reservoir built during the Anuradhapura kingdom by damming the Kanadara Oya, which is the main tributary of the Malwatu Oya. This reservoir has been called Kana Wapi and Kanadiyadora in the ancient to be built by King Mahasena (276-303 CE). It is reported that king Sena II (853-887 CE) had built a weir at a place called Kattaththa and diverted water to Kanadara Oya through a 12-kilometre canal to increase the supply of water to Mahakanadarawa Wewa.
The embankment of the tank is 2.8 km long and covers 34,000 acres (13.76 sq. km) when full. The total water holding capacity is 36 250 acre-feet (44,713,717 cubic meters). Unfortunately, the Anuradhapura — Trincomalee road is built across the tank, bisecting it into two.
(Heritage Lanka by Neil Kiriella 2017, P:213)