Browsing by Author "Perera, B.D.C."

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    Eutrophication Trends in Bolgoda North Lake, Sri Lanka
    (Department of Zoology, University of Kelaniya, Kelaniya, Sri Lanka, 2014-06) Perera, B.D.C.; Wijeyaratne, M.J.S.; Dahanayaka, D.D.G.L.; Tonooka, H.; Minato, A.; Ozawa, S.
    Chlorophyll-a (Chl-a) concentration in the Bolgoda North Lake (06.400 – 06. 480 N; 079. 550 -079. 580 E), which is a shallow brackish water body situated in the western coastal region of Sri Lanka, was determined through correlating Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) optical sensor data with in-situ data measured from April 2013 to October 2013 in 05 sampling sites. ASTER band ratio of B1/B2 which gave the highest correlation with in-situ Chl-a data was used to generate 15 m resolution Chl-a distribution maps. Chl-a distribution maps generated using ASTER data indicated that most areas of Bolgoda North Lake were eutrophic. Some regions of the Weras Ganga which flows into the Lake showed very high Chl-a concentrations during April indicating hypereutrophic conditions while in June, September and October these areas indicated eutrophic conditions. Observations on land use pattern revealed that industrial zones border these areas. High Chl-a concentrations were also observed in the areas bordered by the lands with low income houses from which household waste as well as sewage are discharged directly to the lake. Chl-a distribution maps developed for 2005, 2008, 2010 and 2011 revealed that eutrophication of the Bolgoda North Lake has gradually increased in the recent past. This may possibly be due to the increase in the industrial effluents as a result of industrial development in the area and also due to increased population of low income groups that live in some areas bordering the lake.
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    Monitoring eutrophication trends in Bolgoda North Lake, Sri Lanka by Satellite Remote Sensing
    (Central Fisheries Research Institute (CFRI) Trabzon, Turkey in cooperation with Japan International Cooperation Agency (JICA), Japan, 2016) Dahanayaka, D.D.G.L.; Perera, B.D.C.; Wijeyaratne, M.J.S.; Tonooka, H.
    This study was aimed to determine the present level and past trends of eutrophication of the Bolgoda North lake, Sri Lanka using in situ Chlorophyll-a (Chl-a) measurements and remote sensing data obtained from Advanced Space-borne Thermal Emission and Reflectance Radiometer (ASTER) satellite data. From March to October 2013, Chl-a, nitrate and phosphate contents of the lake were measured once a month on the days of ASTER overpass and using standard laboratory methods. Cloud-free ASTER images of the lake for the 2000-2013 period were atmospherically corrected using Fast Line-ofsight Atmospheric Analysis of Hypercubes (FLAASH) and in-situ Chl-a data were regressed with atmospherically corrected three ASTER Visible and Near Infrared band ratios of the same date. The green/red band ratio, which had the highest coefficient of determination, was used to develop algorithm for generation of 15-m resolution Chl-a distribution maps. Results indicated that eutrophication of this lake has increased from 2008 to 2011. Heavy eutrophic conditions were noted in several regions of the lake in 2013, especially in water stagnant areas and adjacent to freshwater inlets. Unplanned urbanization and inadequate facilities for waste management have resulted in heavy eutrophication of the water body. If the present trends of waste disposal and unplanned urbanization continue, enormous environmental problems would be resulted in future.