Kelani River

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Kelani Ganga is a river in Sri Lanka, beginning in the Sri pada mountain range and flowing into the Indian Ocean at Colombo. It covers 80 percent of the water supply to Colombo. In addition, it is used for hydropower production, transport, 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. http://www.kellnielsen.dk/kelani.htm