The Kelani River (Sinhala: කැළණි ගඟ) is a 145-kilometre-long (90 mi) river in Sri Lanka. The fourth-longest river in the country, it stretches from the Sri Pada Mountain Range to Colombo. It flows through or borders the Sri Lankan districts of Nuwara Eliya, Ratnapura, Kegalle, Gampaha and Colombo. The Kelani River also flows through the capital of Sri Lanka, Colombo, and provides 80% of its drinking water.
Horton Plains National Park (Sinhala: හෝර්ටන් තැන්න ජාතික උද්යානය, romanized: Hortan Thanna Jathika Udyanaya) is a national park in the central highlands of Sri Lanka that was designated in 1988. It encompasses an area of 31 km (12 sq mi) and borders Thotupalakanda Nature Reserve. 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.
The Horton Plains are the headwaters of three major Sri Lankan rivers, the Mahaweli, Kelani, and Walawe rivers. In Sinhala the plains are known as Maha Eliya Plains (මහ එළිය තැන්න). Stone tools dating back to Balangoda culture have been found here. The plains' vegetation is grasslands interspersed with montane forest and includes many endemic woody plants. Large herds of Sri Lankan sambar deer feature as typical mammals and the park is also an Important Bird Area with many species not only endemic to Sri Lanka but restricted to the Horton Plains. Forest dieback is one of the major threats to the park and some studies suggest that it is caused by a natural phenomenon.