Like many of the lakes in Sri Lanka, Minneriya Tank also has a very important history attached to it. Minneriya Tank is another one of the tanks that contributed to the ancient irrigation network in the Anuradhapura Era. Minneriya Tank was built by King Mahasen and the enormous lake spans for more than 4000 acres. This big lake gets its water supply from the Mahaweli River, which is the longest river in Sri Lanka. Even though it was built in ancient times, the lake is still used today by people living nearby. It is also a source of water for the animals that live in the reservoir as well as in the jungles of Minneriya.