Glimpses of Kala Oya Estuary – April 2022

The Kala Oya, 145 Km in length, is the third longest river in Sri Lanka. The river basin 2,873 sq Km in extent is home to a population of over 400,000. The catchment area of the river which is 1,800 sq Km receives around 3,200 million cubic metres of rain per year out of which around 5 percent reaches the sea. The estuary of the Kala Oya is a bay estuary, as the main stream of the Kala Oya and its tributaries discharge freshwater into the Dutch Bay before entering the sea. The estuarine area includes the brackish water areas of Kala Oya, Dutch Bay and the Puttalam Estuary. The amount of freshwater received is controlled by the water retention capacities of the tank system within the Kala Oya basin. Kala Oya estuary harbours the largest tract of intact riverine mangroves in Sri Lanka. This ecosystem functions as an important breeding ground for many marine species and is rich in biodiversity. Presently, the Kala Oya estuary is in good condition as the area is sparsely populated and partially borders Wilpattu National Park. The coastal resources of the vast estuary include varied habitats such as mangroves, sea grass beds, sand dunes, lagoon systems, reefs etc. The Bar Reef Marine Sanctuary (over 300 Sq Km of coral reef) is situated at the sea mouth of the Kala Oya basin.