Hydroelectricity, or hydroelectric power, is electricity generated from hydropower. Hydropower supplies one sixth of the world's electricity, almost 4,500 TWh in 2020, which is more than all other renewable sources combined and also more than nuclear power. Hydropower can provide large amounts of low-carbon electricity on demand, making it a key element for creating secure and clean electricity supply systems. A hydroelectric power station that has a dam and reservoir is a flexible source, since the amount of electricity produced can be increased or decreased in seconds or minutes in response to varying electricity demand. Once a hydroelectric complex is constructed, it produces no direct waste, and almost always emits considerably less greenhouse gas than fossil fuel-powered energy plants. However, when constructed in lowland rainforest areas, where part of the forest is inundated, substantial amounts of greenhouse gases may be emitted.
The Mahaweli River, 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 Mahaweli Ganga starts at Polwathura, 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 natural deep-sea harbours in the world.
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 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.
The Turkwel Hydroelectric Power Station, also Turkwel Dam, is an arch dam on the Turkwel River about 76 km (47 mi) north of Lorokon in Turkana County, Kenya. The dam serves several purposes, including hydroelectric power production, irrigation, tourism and fisheries. It was constructed between 1986 and 1991. It supports the third largest hydroelectric power plant in the country, having an installed electric capacity of 106 megawatts (142,000 hp).
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 of the United Kingdom.
The Samanala Dam is a dam primarily used for hydroelectric power generation in Sri Lanka. Commissioned in 1992, the Samanalawewa Project is the third-largest hydroelectric scheme in the country, producing 405 GWh of energy annually. It was built with financial support from Japan and the United Kingdom. It is notable for a large leak on its right bank. Power production continues as planned despite the leakage, and the water from the leak now provides two thirds of the water issued by the reservoir for agriculture in downstream areas.
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.
The Ubol Ratana Dam, formerly known as the "Phong Neeb Dam", is a multi-purpose dam in tambon Khok Sung, Ubolratana district, approximately 50 km (31 mi) north of Khon Kaen, Khon Kaen province, Thailand. It was the first hydroelectric power project developed in Thailand's northeastern area of Isan. The dam impounds the Nam Phong, which flows into the Chi River and thence to the Mun River, a tributary of the Mekong River. The dam was given its current name by royal permission in 1966, in honour of princess Ubol Ratana, the eldest child of King Bhumibol Adulyadej.
The Broadlands Dam is a 35 MW run-of-the-river hydroelectric complex currently under construction in Kitulgala, Sri Lanka. The project is expected to be completed in 2020, and will consist of two dams, and a power station downstream.
The Moragahakanda Dam, officially 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 water release of the dam was in January 2017. Morgahakanda/Kaluganga project is the last of the Great Mahaveli project
The Laxapana Dam is a gravity dam built across the Maskeliya Oya, 2.8 km (1.7 mi) downstream of the Laxapana Falls, in the Central Province of Sri Lanka.
The Kehelgamu Oya is a major upstream tributary of the Kelani River. The tributary measures 50 km (31 mi) in length, originating in the hills of the Horton Plains National Park, before passing through the Castlereigh Reservoir. Kehelgamu Oya converges with the Maskeliya Oya at Kalugala, forming the 100 km (62 mi) long Kelani River. The river is heavily used for hydroelectric power generation.
The Kulekhani Dam is a rock-fill dam on the Kulekhani River near Kulekhani in the Indrasarowar Rural Municipality of Makwanpur District in Bagmati Province, Nepal. The primary purpose of the dam is hydroelectric power generation and it supports the 60 MW Kulekhani I, 32 MW Kulekhani II and 14 MW Kulekhani III Hydropower Stations. Construction began in 1977 and Kulekhani I was commissioned in 1982. Kulekhani II was commissioned in 1986 and a third power station, the 14 MW Kulekhani III was expected to be commissioned in May 2015 but was delayed due to issues with the builder. The US$117.84 million project received funding from the World Bank, Kuwait Fund, UNDP, Overseas Economic Cooperation Fund and OPEC Fund. It is owned by Nepal Electricity Authority.
The Vorotan Cascade, or the ContourGlobal Hydro Cascade, is a cascade on the Vorotan River in Syunik Province, Armenia. It was built to produce hydroelectric power and provide irrigation water. The Vorotan Cascade consists of three hydroelectric power plants and five reservoirs with a combined installed capacity of 404.2 MW. It is one of the main power generation complexes in Armenia.
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 the keystone of the government's development program that was initiated in 1961.
The Uma Oya Hydropower Complex (also internally called Uma Oya Multipurpose Development Project or UOMDP) is an irrigation and hydroelectric complex currently under construction in the Badulla District of Sri Lanka. Early assessments of project dates back to 1989, when the first studies was conducted by the country's Central Engineering and Consultancy Bureau. The complex involves building a dam across Dalgolla Oya, and channelling water over a 3,975 m (13,041 ft) tunnel to Mathatilla Oya, both of which are tributaries of the Uma Oya. At Mathatilla Oya, another dam is constructed to channel 145,000,000 m3 (5.1×109 cu ft) of water per annum, via a 15,290 m (50,160 ft) headrace tunnel to the Uma Oya Power Station, where water then discharged to the Alikota Aru via a 3,335 m (10,942 ft) tailrace tunnel. The Alikota Aru is a tributary of the Kirindi Oya.
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.
