|• location||Horton Plains National Park|
|Mouth||Bay of Bengal|
|Length||335 km (208 mi)|
|Basin size||10,448 km2|
|• left||Amban Ganga|
|• right||Kotmale Oya|
The Mahaweli River (Sinhala : මහවැලි ගඟ, literally "Great Sandy River"; Tamil : மகாவலி ஆறு [mahawali gangai]), is a 335 km (208 mi) long river, ranking as the longest river in Sri Lanka. It has a drainage basin of 10,448 km2 (4,034 sq mi), the largest in the country, which covers almost one-fifth of the total area of the island. The real beginning of Mahaweli Ganga starts at Polwathura(at Mahawila area), a remote village of Nuwara-Eliya District in bank Nawalapitiya of Kandy District by further joining of Hatton Oya and Kotmale Oya. The river reaches the Bay of Bengal on the southwestern side of Trincomalee Bay. The bay includes the first of a number submarine canyons, making Trincomalee one of the finest deep-sea harbors in the world.
As part of Mahaweli Development programme the river and its tributaries are dammed at several locations to allow irrigation in the dry zone, with almost 1,000 km2 (386 sq mi) of land irrigated. 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.
There is a misconception in Sri Lanka that the Mahaweli starts in the Sri Pada mountain. The Mahaweli gets its source waters from Horton Plains in Kirigalpoththa and the Thotupola mountain range.
The Mahaweli River Starts from Polwathura/ Mahavila area with water source starting from the Horton Plains National Park.
Sri Lanka, formerly called "Ceylon", is an island nation in the Indian Ocean, southeast of the Indian subcontinent, in a strategic location near major Indian Ocean sea lanes. The nation has a total area of 65,610 square kilometres (25,330 sq mi), with 64,630 square kilometres (24,950 sq mi) of land and 980 square kilometres (380 sq mi) of water. Its coastline is 1,340 kilometres (830 mi) long. The main island of Sri Lanka has an area of 65,268 km2; it is the twenty-fifth largest island of the world by area. Dozens of offshore islands account for the remaining 342 km2 area. The largest offshore island, Mannar Island, leads to Adam's Bridge.
Horton Plains National Park is a national park in the central highlands of Sri Lanka that was designated in 1988. It is located at an elevation of 2,100–2,300 m (6,900–7,500 ft) and encompasses montane grassland and cloud forest. It is rich in biodiversity and many species found here are endemic to the region. It is also a popular tourist destination and is situated 8 kilometres (5.0 mi) from Ohiya, 6 kilometres (3.7 mi) from the world-famous Ohiya Gap/Dondra Watch and 32 kilometres (20 mi) from Nuwara Eliya.
Sri Lankan state-sponsored colonization schemes is the government program of settling mostly farmers from the densely populated wet zone in the sparsely populated areas of the dry zone in the North Central Province, Southern Province, Uva Province, Sabaragamuwa Province, Northern Province and the Eastern Province regions near tanks and reservoirs being built in major irrigation and hydro-power programs such as the Mahaweli project to create farming and fishing communities. This has taken place since the 1950s.
Nawalapitiya is a town in Central Province, Sri Lanka.
The Kotmale River is the longest tributary of Mahaweli River. The river begins as the Agra Oya, in the Horton Plains. The Central Plains have an annual rainfall of between 125 and 200 inches a year. The river is approximately 70 km (43 mi) long and drains a basin of about 58,534 ha. The river flows through a traditional area of ancient villages and tea plantations. King Dutugemunu spent his youth here. The Kotmale Oya flows into the Mahaweli shortly at Pallegama. Tributaries of the Kotmale Oya include the Nanu Oya, the Pundalu Oya, the Puna Oya, and the Dambagastalawa Oya.
St. Clair's Falls is one of the widest waterfalls in Sri Lanka and is commonly known as the "Little Niagara of Sri Lanka". It is one of six waterfalls affected by the Upper Kotmale Hydropower Project.
Victoria Dam is an arch dam located 130 mi (209 km) upstream of the Mahaweli River's mouth and 4 mi (6 km) from Teldeniya. It is named in honor of Queen Victoria.
The Upper Kotmale Dam is located in Talawakele, within the Nuwara Eliya District, in the Central Province of Sri Lanka. The dam feeds the third largest hydroelectric power station in the country.
Kantale is a town in the Trincomalee District in eastern Sri Lanka. The town is located 38 km (24 mi) south-west of Trincomalee.
The Moragahakanda Dam, officially as Kulasinghe Reservoir, is a large gravity dam, and the main component of the larger and more complex Moragahakanda — Kalu Ganga Project, across the Amban River at Elahera, in the Matale District of Sri Lanka. Construction began on 25 January 2007 and was completed in 2018. The maiden waters of the dam was released in January 2017. Morgahakanda/Kaluganga project is the last of the Great Mahaveli project
The Kalu Ganga Dam is a large gravity dam, and the second vital component of the larger and more complex Moragahakanda — Kalu Ganga Project, currently under construction across the Kalu Ganga at Pallegama, in the Matale District of Sri Lanka. This Kalu Ganga is a tributary of Amban Ganga which is itself a tributary of the Mahaweli River the longest river in Sri Lanka. This shall not be confused with Kalu Ganga. Construction of the project was launched by President Mahinda Rajapaksa on 25 January 2007. The maiden waters of the dam was released in July 2018.
Bakamuna is a village town in Sri Lanka. It is located within North Central Province.
Nanu Oya is a 27 km (17 mi) long stream in the Central Province of Sri Lanka It originates from Pidurutalagala at an elevation of over 2,000 m (6,562 ft) and drains into the Kotmale Oya at an elevation of approximately 1,200 m (3,937 ft). The Kotmale Oya is a tributary of the Mahaweli River, the longest river in Sri Lanka, which finally discharges at Trincomalee after a combined distance of nearly 350 km (217 mi). The river was dammed in 1873 to create the popular Lake Gregory in Nuwara Eliya. The Nanu Oya discharges into the Kotmale Oya 2.5 km (1.6 mi) upstream of the Upper Kotmale Dam.
Iranamadu Tank is an irrigation tank in northern Sri Lanka, approximately 3 mi (5 km) south east of Kilinochchi.
The Mahaweli Development program is known as the largest multipurpose national development program in the history of Sri Lanka and is also considered as the keystone of the government's development program that was initiated in 1961.
The Maduru Oya Dam is an irrigation dam built across the Maduru Oya. The embankment dam measures 1,090 m (3,580 ft) in length, 41 m (135 ft) in height, and creates the Maduru Oya Reservoir. The reservoir has a catchment area of 453 km2 (175 sq mi) and a storage capacity of 596,000,000 cubic metres (2.10×1010 cu ft) The proposed Maduru Oya Solar Power Station is to be built over the surface of the Maduru Oya reservoir.
The Moragolla Dam is a planned hydroelectric dam in Moragolla, Sri Lanka. The dam is to be 35 m (115 ft) high and is planned to create the 1,980,000 m3 (70,000,000 cu ft) Moragolla Reservoir with a maximum supply level at 548 m (1,798 ft) MSL. Upon completion, the Moragolla Power Station would have a gross installed capacity of 30 megawatts from two francis turbines, capable of generating approximately 85 GWh annually.