International Research Symposium on Pure and Applied Sciences (IRSPAS)

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    Estimation of crop management factor and conservation support practice factor of RUSLE model to assess vulnerability to soil erosion in Kalu Oya and Mudun Ela basins using GIS
    (Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Lekamge, M. L. D.; Dayananda, M. D. N. R.; Weerasinghe, V. P. A.
    Soil erosion is a serious environmental problem, which emerges from intense anthropogenic activities, agricultural practices and improper land use management. River basin soil erosion assessment enables to plan, conserve and manage the watershed areas and associated ecosystems. Revised Universal Soil Loss Equation (RUSLE) model is the most widely used model to predict the long term erosion rates in an area using rainfall-runoff erosivity factor, soil erodibility factor, slope length and steepness factor, crop management factor (C factor) and conservation support practice factor (P factor). Present study has been conducted to estimate the C and P factor to assess the vulnerability to soil erosion in Kalu Oya and Mudun Ela basins located in Gampaha district, Western province, Sri Lanka. The total catchment area of Kalu Oya and Mudun Ela basins (7°7'60" N and 79°54'0" E) are about 78 km2. C and P factor of RUSLE model were estimated using land use map and 30m resolution LANDSAT 8 OLI/TIRS satellite images acquired on 17th February, 2018 to determine the vulnerability of erosion and conservation status. The C factor values for barren areas and well protected areas were assigned from 1 - 0 respectively, whereas 0 - 1 range was used for the good conservation (0) and poor conservation (1) status of the prevailing land use patterns using the field observations and literature reviews. Spatial join tool of overlay analysis was used to obtain the combined effect of C and P factors and two separate thematic maps were derived using ArcGIS 10.2.2 version to represent the spatial distribution of both C and P factors according to five classes; low, moderate, high, very high and extremely high which represent the vulnerability to soil erosion. The study identified 9.94% of the total area with 0.00 - 0.01, 80.56% with 0.01 - 0.14, 0.61% with 0.01 - 0.20, 8.03% with 0.20 - 0.63 and 1.86% with 0.63 - 1.00 of C factor and 0.01% with 0.20, 0.61% with 0.20 - 0.40, 82.57% with 0.4 - 0.5, 1.45% with 0.50 - 0.60, 15.35% with 0.60 - 1.00 P factor. Significantly higher amount of erosion vulnerability areas were observed besides the tributaries. The study identified 9.01% of the total area under low erosion (0.00 - 0.02), 79.56% under moderate erosion (0.02 - 0.14), 0.61% under high erosion (0.14 - 0.20), 8.03% under very high erosion (0.20 - 0.63) and 1.86% under extremely high erosion (0.63 - 1.00) for combined effect of C and P factor. Moderate erosion could be reduced using suitable agronomic practices. Appropriate conservation measures have to be implemented for the areas under high, very high and extremely high vulnerability to soil erosion within the Kalu Oya and Mudun Ela basins to reduce sediment transport.
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    Distribution of Pemphis acidula to enhance conservation measures in Puttalam lagoon, Sri Lanka.
    (International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Gunathilaka, M. D. K. L.
    Pemphis acidula have identified as a mangrove associate species, which is a rare species limited only to Puttalam lagoon area. This is identified as a near threatened species in Sri Lanka. The study aimed to identify the distribution of P acidula in Puttalam lagoon area and to suggest conservation measures using primary and secondary data. Field survey and interviews were used to obtain primary data. Hundred individuals, live along the periphery of lagoon were interviewed to evaluate threats and awareness of P acidula. Vegetation sampling were performed for randomly selected 25 sample sites (S1-S25) to find out the distribution of species in the lagoon area. The sample size was 5m ᵡ 5m. Water samples were also collected at the same locations to measure salinity of the lagoon water. Arc GIS mapping techniques and MS excel 2016 version were used for data analysis. The species were enumerated in identified four particular areas in Puttalam lagoon area. Higher distribution was identified towards to the ocean. In addition, the species was also present in Kalpitiya mainland. The preferable salinity level of the species was reported as between 26-30 g/L. Therefore, considering the salinity in the study area, Kala oya estuary area and Dutch bay area were identified as most suitable areas for the distribution of the plant. P acidula were not present in the sites where salinity was less than 20g/L, which indicated that the species prefer high salinity levels. P acidula, which has high potential to exterminate dengue larvae and have strong antibacterial activity has been reduced drastically due to clearings of mangroves. Though the species are important for industrial and pharmaceutical purposes, there are no conservation measures to protect the species at present. The unawareness of coastal residents live along the periphery of the lagoon was about 90% and the threat has been increased as people used to destroy the plant for firewood. Therefore, conservation measures should be introduced using appropriate methods such as demarcations of buffer zones, to prevent removing the plants. Regular research and observations are important to keep updated records on number and distribution of this species. Northern-most parts in the lagoon where the salinity level is high as 26-30 g/L were identified as possible restoration sites of P acidula. As it is an invaluable plant, it is timely important to conserve P acidula population in Puttalam lagoon area.