King Parakramabahu, the ruler of Polonnaruwa at the time, built this colossal reservoir spreading over 2400 hectares, which filled-up number of minor tanks with network of irrigation system. The tank was originally consist of 5 large reservoirs naming Thopa wewa, Eramudu Wewa, Dumbuthulu Wewa, Kalahagala Wewa and Bhu Wewa in-order to reduce the pressure of the main dam.
Located in the dry zone, Polonnaruwa suffered from lack of water and the poor irrigation system with not enough to supply for the agricultural needs. King Parakramabahu took the initiative to collect every drop of monsoon rain water by creating over 53 tanks in order to enrich and amplify the rice production and agricultural industry all together, providing safe water and sanitation services to the community. Hence the name “wew Bendi Rata” (Country of Reservoirs) was used to describe Polonnaruwa.