Nuwara wewa in Anuradhapura is one of the most important irrigation feats of the ancient engineers of Sri Lanka. According to the historical information the tank was built in the 1st century BC. The tank was built under the patronage of King Vattagamini Abhaya. Bund of this gigantic tank is 3 miles long and average height is estimated to be 37 feet. The water surface of the tank spreads over 3180 hectares of land in the ancient city of Anuradhapura. The water of Malwatu River was diverted to the tank by a dam across the river. This ancient tank is still being used for irrigation and to fulfil other water requirements of the people in the area.
The tank and the immediate surrounding had been an important area with rich bio-diversity that developed for thousands of years. But today the Eco-system around the tank is largely changed and its value has been severely affected. The riverine areas of the tanks were harbouring a large number of fauna and flora species, but by 2003 most of this riverine environment were destroyed due to the human activities. Unfortunately, the valuable forest cover of the catchment area around the tank is also removed during the past few decades. The vegetation of the surrounding area is comprised of 25 species of hardwood trees and several species of shrubs. With the expanding human pollution, the usage of forest resources is also significantly increased in the past. The trees are removed get wood, firewood and, some people remove them for agriculture purposes. Here you can see the forest is used in an unsustainable manner so that during the period of 1956 to 2003, almost whole valuable forest in the catchment area is removed.