It was constructed and expanded under King Parakramabahu I between 1153 and 1186 AD, covering about 22.6 square kilometers.

The reservoir was formed by linking smaller tanks including Topa Wewa, Eramudu Wewa, and Dumbutulu Wewa into one expansive water body.

Its earthen dam extends over 12 kilometers, forming one of the largest ancient irrigation structures in Sri Lanka.

King Parakramabahu expressed his principle of water use as

“Not even a drop of water must go to the sea without being used.” - King Parakramabahu (1123–1186 AD).

The remains of a summer palace, identified by some as the Seetha Maligaya, can still be seen on a small island within the reservoir.