Maha Oya (මහ ඔය)

The Malvathu River  long river in Sri Lanka, connecting the city of Anuradhapura, which was the capital of the country for over 15 centuries, to the coast of Mannar. It currently ranks as the second longest river in the country, with a great historic significance.

The Kelani River is a 145-kilometre-long (90 mi) river in Sri Lanka. Ranking as 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 Yan Oya is the fifth-longest river of Sri Lanka. It measures approximately 142 km (88 mi) in length. Its catchment area receives approximately 2,371 million cubic metres of rain per year, and approximately 17 percent of the water reaches the sea. It has a catchment area of 1,520 square kilometres.

The southern region of Sri Lanka is exalted by a bushel of enthralling and glorified rivers and the Walawe River is one of them. Gently flowing through the Udawalawe National Park, the Walawe River provides water for a multitude of species of mesmerising fauna.

Kalu Ganga is a river in Sri Lanka. Measuring 129 km (80 mi) in length, the river originates from Sri Padhaya and reach the sea at Kalutara. The Black River flows through the Ratnapura and the Kalutara District and pass the city Ratnapura. The mountainous forests in the Central Province and the Sinharaja Forest Reserve are the main sources of water for the river.

The Maha Oya is a major stream in the Sabaragamuwa Province of Sri Lanka. It measures approximately 134 km (83 mi) in length. It runs across four provinces and five districts. Maha Oya has 14 Water supply networks to serve the need of water and more than 1 million people live by the river.

The Gin Ganga, is a 115.9 km (72 mi) long river situated in Galle District of Sri Lanka. The river's headwaters are located in the Gongala Mountain range, near Deniyaya, bordering the Sinharaja Forest Reserve.

It was around these ancient tank (water storage reservoir) irrigation systems that the economy and human settlements of early Sri Lankan society were organised into a “hydraulic civilization”.

The Deduru Oya Dam is an embankment dam built across the Deduru River in Kurunegala District of Sri Lanka. Built in 2014, the primary purpose of the dam is to retain approximately a billion cubic metres of water for irrigation purposes, which would otherwise flow out to sea.

The Maduru Oya is a major stream in the North Central Province of Sri Lanka. It is approximately 135 km (84 mi) in length. Its catchment area receives approximately 3,060 million cubic metres of rain per year, and approximately 26 percent of the water reaches the sea.

The Kumbukkan Oya is the twelfth-longest river of Sri Lanka. It is approximately 116 km (72 mi) long. It runs across two provinces and two districts. Its catchment area receives approximately 2,115 million cubic metres of rain per year, and approximately 12 percent of the water reaches the sea.

The Mi oya is a 108 km (67 mi) long river, in North Western of Sri Lanka. It is the fifteenth-longest river in Sri Lanka. It begins in Saliyagama and flows northwest, emptying into the Indian Ocean thru Puttalam.