Land use of the kelani river basin

The key categories of green cover in the Kelani River Basin are the Forests, Home Gardens, Rubber and Tea plantations. However, this land use classification is not done at a high resolution and ground trothing is not used extensively in determining the exact canopy type. Therefore, it is not advisable to use this for detailed decision making other than the general use. There are a number of new initiatives by the Survey Department and others to update the land cover. For example, the World Bank is supporting the Survey Department to develop an accurate land use map of Kelani River Basin in collaboration with the European Space Agency using the satellite imagery for 1991, 2001 and 2012. Survey Department is also starting a LIDAR survey for the western province under JICA support. SLLRDC has a LIDAR data set for the Metro Colombo area. The Land Use Policy Planning Unit (LUPPD) is also in the process of updating the land use data.

Roads and Streams

Roads, related infrastructure and drainage are closely linked to water quality, quantity and development issues such as soil erosion, altered hydrology and flooding, deforestation, damage to valuable ecosystems and habitats, damage to scenic quality and tourism and human health and safety. For example, the open road cuts (new constructtion or old) has the potential to release sediments during intense rain events. In addion oil, greese and other petrolium based chemicals can get washed into streams along with storm water. At the same time the stream banks are also sensitive to intense rainfall and high sediments can be released to the natural system.

Industries

About 2, 840 industries are recorded in the CEA database with different pollution potentials (Type A, B and C). The 2, 840 industries are divided into 862 (30%); 1, 220 (43%); and 760 (27%) among A, B and C type of industries, respectively. Their distribution of industries among the 20 sub-watersheds are provided in Annexure 4. In the Kelani River Basin (KRB) the Industrial Effluent Discharge of the industries at the Biyagama EPZ is treated by a conventional treatment facility available at site and discharged into Kelani River through Rakgahawatta canal which is located upstream of water intakes of Ambathale and Kelani Right Bank water treatment plants.

Agriculture and Animal Husbandry

Several large and medium scale private owned tea and rubber estates are located in the Kelani Basin. Further, there are a large number of small and medium scale tea, rubber, coconut and cloves plantations located within the Kelani River Basin. Rambutan and Durian are two of the major fruit crops grown in the Kelani valley that are not depicted in the national accounts. In addition, fruit varieties such as banana, pineapple and a range of vegetables are grown in the Kelani River Basin. Subsistence fisheries, collection of aquatic plants and flowers, non-timber forest products such as “ Kithul” based products are some of the minor livelihood practices found in the Kelani River Basin. A large number of minor irrigation projects in the Colombo and Gampaha districts are based on the Kelani River or its tributaries supporting about 150 sq. kilometres of paddy lands and a range of other crops. The same schemes are being used for flood control to a greater extent.