Sri Lanka's rivers

There are 103 rivers and streams with most flowing from the upcountry mountains of Sri Lanka. The longest is the Mahaweli. It starts its 333 km journey near Adam’s Peak and finds its way into the Indian Ocean at Koddiyar Bay at Trincomalee. It is the only perennial river to cross the dry Zone. Sri Lanka’s perennial rivers are called Ganga,and other streams are called Oya in Sinhala or Aru in Tamil. A number of rivers have now been developed both for irrigation and power. The Victoria power project on Mahavali Ganga is one of the largest in Asia. The other power projects are Kothmale, Rantambe and Randenigala on the Mahaveli river.
Kala - Oya starts from Kalawewa Reservoir built in the 5th Century.
Other rivers which are over 100 Kms long:
Name of River Length
Mahaweli Ganga 335 km
Aruvi Aru 164 km
Kala Oya 148 km
Kelani Ganga 145 km
Yan Oya 142 km
Deduru Oya 142 km
Walawe Ganga 138 km
Maduru Oya 135 km
Maha Oya 134 km
Kalu Ganga 129 km
Kirindi Oya 117 km
Kumbukkan Oya 116 km
Menik Oya 114 km
Gin Ganga 113 km
Mi Oya 109 km
Gal Oya 108 km

Mahaweli

The Mahaweli River is a 335 km long river, ranking as the longest river in Sri Lanka. Its drainage basin is the largest in the country, and covers almost one-fifth of the total area of the island. The river reaches the Bay of Bengal on the southwestern side of Trincomalee Bay. The bay includes the first of number submarine canyons, making Trincomalee one of the finest deep-sea harbors in the world. The river and its tributaries are dammed at several locations to allow irrigation in the dry zone, Production of hydroelectricity from six dams of the Mahaweli system supplies more than 40% of Sri Lanka's electricity needs. One of the many sources of the river is the Kotmale Oya.

Kealani

The Kelani River is 145 km Long River in Sri Lanka. Ranking as the fourth longest river in the country, it stretches from the Sri Pada Mountain Range to Colombo. It covers approximately 80% of the water supply to Colombo. In addition to that, the river is used for transport, fisheries, sewage disposal, sand mining and for production of hydroelectricity. Due to these, many people depend on the river for their daily routine in life.