Kelani Ganga

Kelani Ganga is not the largest river of Sri Lanka, but one of the most important. It covers 80 percent of the water supply to Colombo. In addition, it is used for hydropower production, transport, irrigation, fisheries, and sewage disposal, and sand is extracted from its bed. In these ways, many people depend on the river for their daily life.
The flow varies between 800-1500 m³/s during the monsoon and some 20-25 m³/s in the dry season, depending on the operation of 3 reservoirs in the catchment. There is no regulation at the mouth.

The annual sand extraction is 600-800,000 m³ per year. The sand is mined exclusively by hand. From a moored barge, people dive to the river bed, from where the sand is lifted to the barge in a bucket. When the barge is full, it is taken to the bank, and the sand is unloaded by a separate team.
The sand mining causes the river bed to sink by some 10 cm per year.
At present, two main concerns in connection with the river are:
· Flooding during the monsoon
· Saline intrusion in the dry season
The problems are related. The saline intrusion is enhanced by the deepening of the river caused by the sand mining, but this acitivity is economically important, both nationally, and from the point of view of the many involved people. Regulation in order to prevent the saline intrusion can reduce the water quality in other ways, and can increase the flood risk.
In the future, the dry season flow will become inadequate for urban supply and irrigation. Further, the water quality may be affected by pollutants and pesticides from the agriculture.

mahaweli ganga

Mahaveli Rever



The longest river of Sri Lanka, the Mahaweli, traverses a course of about 330 km (about 205 mi). . Its drainage basin is the largest in Sri Lanka, and covers almost one-fifth of the total area of the island. The river reaches the Bay of Bengal at Trincomalee in the north-east of Sri Lanka. It continues as a major submarine canyon, making Trincomalee one of the finest deep sea harbours in the world. The river is heavily dammed in order to produce hydroelectricity and water for irrigation. This has brought almost 1,000 km² of land under irrigationMahaweli Ganga is a Sinhalese term that means "great sandy river." The river receives the Kotmale Oya

It flows northeastward across the central highlands and empties into the Bay of Bengal near the port of Trincomalee, on the eastern coast. The country’s second longest river is the Aravi Aru, traversing about 220 km (about 135 mi) on a northwestward course, from the central highlands to the Gulf of Mannār.
Sri Lanka has no natural lakes. Dams on the Mahaweli and other rivers have created large reservoirs. In addition, a series of small reservoirs called tanks dot the north central plains, storing water during the dry season. Some of the tanks were constructed as many as 2,000 years ago.

walawe river

The Walawe basin, drained by these and smaller water courses, covers an area of 956 square miles (612,000 acres)
The rainfall in the upper reaches of the basin is over 100 inches per year on the average, while at Ambalantota near the river mouth, it is below 40 inches per year. The river discharges 1,100,000 acre feet of water into the sea annually. The development area under the Walawe Basin Project, includes two small areas, extending on the east upto the Malala oya and on the west upto Urubokka oya.

The walawe irrigation system in Southern Sri Lanka draws water from the Uda Walawe reservoir on the Walawe Ganga. There are two main canals on the right and left banks respectively, which flow through several smaller tanks on tributaries of the Walawe, and which cotribute to the system’s water resources.

The Uda Walawe reservoir constructed across Walawe Ganga at Uda Walawe has a capacity of 268 million cubic meters (MCM) or 217,800 ac.ft. The irrigated area is fed through two main canals, one on the Right Bank and the other on the Left Bank. These canals flow through several smaller tanks on tributaries of the Walawe basin which also contribute to the overall project water resources. The RBMC is a single banked canal for most of its 40.9 km and therefore collects some direct runoff from the adjacent higher ground. The Right Bank Main Canal empties into Chandrikawewa 17 km below the main reservoir and then takes off through a regular at the southern end to supply water to the balance 24 km of the RBMC

Towards the north of the sanctuary near the Walawe River the shy Sambur and herds of spotted Deer roam in the thicket. Leopards and Bear inhabit the Rocky areas and are rarely met. The bird life is profuse in this park. The immaculate white Egrets, GrayPelicans, Colorful painted Stork. Gray Herons and King Fishers in all there varieties are found here. The greedy fishing bird Cormorant's together with Spoonbills and monitor Lizards are found by the water holes. Birds of prey the Brahiminy Kite and Serpent Eagle hover above. Peafowl and jungle Fowl (The Sri Lankan national Bird) is found in abundance. Towards the north lining the river are the Kumbuk Trees with their unmistakable polished bark and whose roots are said to purify the water. From top of these trees Hornbills and Gray Languars call each other in metallic discords. Medicinal trees like Aralu, Bulu, Nelli and expensive timbers such as Teak, Ebony and Halmilla are found in the park together with fruit trees like Palu, Weera and Dimbul, the choice morsel of Elephants.

Malvathu oya

The Malvathu River (also known as Malvathu Oya locally in Sinhala) is a 164 km (102 mi) 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 northern part of the river, and sometimes the whole river, was once been known as Aruvi Aru, the most recent Tamil allonym.