Symposia & Conferences
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Item Forecasting the next decade of mean annual rainfall based on historical rainfall data and CHIRPS data using RStudio(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Perera, W. W. A. M. R.; Weerasinghe, V. P. A.; Nawarathna, D. A. G. S. K.Rainfall is a very crucial event that significantly influences environmental conditions. To address adverse environmental scenarios, rainfall analysis is essential. This study aims to predict annual rainfall patterns for the next 10 years across 9 rainfall stations in Sri Lanka and visualize these predictions through graphs. Daily rainfall data from 1992 - 2022 were collected from the Department of Meteorology in Colombo, Sri Lanka. And, the CHIRPS data from the Climate Hazard Centre at the University of California, Santa Barbara, were utilized as a parallel data source to ensure the accuracy of the statistical tests performed. The collected rainfall data were processed to calculate annual rainfall values for each rainfall station in Sri Lanka. Annual rainfall values for the past 30 years were statistically analyzed by undertaking simple exponential smoothing statistical tests using RStudio software and whereby line scatterplots were derived for next 10 years for each rainfall station. This simple exponential smoothing is a time series forecasting method used to predict future values based on past data. According to the results, the highest average annual rainfall increment can be expected in Ratnapura rain gauge station which is 4247 mm. Satellite-based rainfall data corroborated these findings, predicting an average annual rainfall as 3968 mm for the same rain gauge station. Conversely, the lowest average annual rainfall is expected at the Hambantota rain gauge station, indicating 839 mm/year based on rain gauge data. According to the CHIRPS database, it is 1106 mm/year. However, the methodology does not account for major climate phenomena such as El Nino Southern Oscillation (ENSO) and the Madden-Julian Oscillation in the Indian ocean. This means, Sri Lanka may experience an increment in annual rainfall from 2023 to 2033 due to alterations that have already happened in climate. Hence, it is very important to be aware that responsible parties undertake necessary actions to tackle potential adverse situations in the future.Item Assessing urban heat island dynamics: A comparative study of Colombo district in 2015 and 2022(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Perera, A. A. I. U.; Dickowita, D. K. R. R.; Rathnayaka, W. R. A. J. W.; Weerasinghe, V. P. A.Widespread industrialization and migration of the rural population to urban areas have led to rapid urbanization. This phenomenon transforms permeable surfaces into impermeable surfaces, leading to an increase in land surface temperature. This accelerates the formation of urban heat islands. Colombo city can be considered as the commercial capital of Sri Lanka. It is a densely populated and highly urbanized city. Over the past few years, residents have experienced discomfort due to elevated temperatures in the Colombo district. Hence, it is necessary to implement mitigation measures to reduce the impact of urban heat islands. Therefore, this study aims to identify urban heat islands in the Colombo district to facilitate the implementation of mitigation measures. To compare the urban heat island effect in Colombo district between 2015 and 2022, two Landsat 8 images with a cloud cover less than 10% were obtained from USGS Earth Explorer. Land surface temperature (LST) for both years was calculated using ArcGIS 10.8 software, utilizing bands 4, 5, and 10. Various equations were applied to determine Top of Atmosphere Radiance, Brightness Temperature, NDVI, Land Surface Emissivity, and finally LST. The LST data was then extracted for Colombo district, and another equation was used to generate a spatial distribution layer of urban heat islands for both years. When comparing the results obtained from the map of 2015 and 2022, an increase in the critically high urban heat island areas was observed, along with a relative decrease in the critically low urban heat islands. In conclusion, the comparative analysis of Urban Heat Islands (UHI) in the Colombo District for 2015 and 2022 shows significant temporal variations in thermal patterns. There is an increase in UHI intensity, which relates to the higher Land Surface Temperatures obtained according to the methodology, highlighting the dynamic nature of urban heat in rapidly developing regions. The spatial distribution of UHI effects proves considerable changes, with previously cooler areas showing intensified warming trends. The reasons for these could be land cover changes, such as increased impervious surfaces and reduced green spaces, playing a crucial role in UHI formation.Item Land-use Change of Muthurajawela Wetland from 2013-2023 using Remote Sensing and Geographic Information System(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Senanayake, S. A. S. J.; Balasooriya, T. A. P.; Vilvarashah, B.; Jayalal, H. A. N. A.; Pitawala, L. M. K. G.; Weerasinghe, V. P. A.Muthurajawela marsh, Sri Lanka's largest coastal saltwater peat bog, is located on the western coast and spans from Wattala to Negombo. This wetland, along with the Negombo Lagoon, forms a sustainable ecosystem and serves as an economical source and a drainage area. It has faced significant depletion due to industrialization and urbanization since 1997, with accelerated changes in the last decade. This signified a need to analyse land-use changes to develop effective conservation strategies. Remote sensing and GIS technologies were proposed for this assessment to formulate future conservation management plans. The main objective of the study involved identification of land-use patterns which occurred in the Muthurajawela wetland over the past 10 years. Specific objectives included the analysis and processing of necessary data to produce land-use maps via GIS and remote sensing and the quantification of land-use change over the study period. Landsat 8/9 OLI images of the Muthurajawela wetland for the years 2013, 2018 and 2023 were obtained from EOS Data Analytics (EOSDA) LandViewer and each image was analysed using ArcGIS software after pre-processing. Supervised classification was carried out on the clipped images under three classes: water bodies, marshlands, urbanization, and land-use maps were prepared. Areas and percentage differences of the selected classes were calculated. Accuracy assessment was carried out using Kappa coefficient. The analysis revealed that, from 2013 to 2018, water bodies decreased by 26.02% (from 0.3571 to 0.2642 km2), urbanization decreased by 16.71% (from 0.6827 to 0.5723 km2), while marshlands increased by 27.38% (0.2931 to 0.3734 km2). From 2018 to 2023, water bodies increased by 24.94% (from 0.2642 to 0.3301 km2), urbanization increased by 11.83% (from 0.5723 to 0.64 km2), and marshlands decreased by 10.69% (from 0.3734 to 0.3335 km2). From 2013 to 2023, water bodies have decreased 1.07%, marshlands increased by 16.7%, and urbanization decreased by 4.34%. Calculated Kappa coefficients were 89.17 for 2013, 74.25 for 2018, and 91.98 for 2023. These high Kappa values indicated a strong agreement between the classified maps and the ground truth data. The overall accuracy values were above 80% for all years (93.33% for 2013, 95.00% for 2018, 86.67% for 2023). Land-use of Muthurajawela marsh resulted in an increase in marshland area from 2013 to 2023, indicating growth of the marshland along with a slight percentage decrease in water bodies and a reduction in land development for urbanization. Although measures taken to restore marshlands appear successful, further measures to protect water bodies are recommended to be applied after further research. Therefore, this analysis has displayed the dynamic nature of the land-use of the wetland ecosystem along with its interactions with human activities.Item Evaluation of spatial and temporal patterns in groundwater quality in the Kalpitiya peninsula(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Fernando, S. N. I.; Weerasinghe, V. P. A.; Mathota Arachchige, Y. L. N.The study investigates the spatial and temporal variation of groundwater quality within the unconfined sandy aquifers of the Kalpitiya Peninsula, Sri Lanka, focusing on four Grama Niladari (GN) divisions: Thethapola, Nawakkaduwa, Narakkaliya, and Kandakuliya Kudawa. These divisions were strategically selected to represent different land-use practices, with groundwater samples collected from 40 agricultural and drinking water wells between October 2023 and January 2024. Selected water quality parameters were assessed using standardized analytical methods. The impact of spatial location and seasonal variation on these parameters was statistically evaluated using the General Linear Model (GLM), followed by Tukey’s pairwise comparison. The results reveal significant spatial variations in groundwater quality across the studied GN divisions, with the highest concentrations of several key parameters observed in Nawakkaduwa. Specifically, Nawakkaduwa exhibited the highest electrical conductivity (EC) (1948.40 ± 5.99 µS/cm), total dissolved solids (TDS) (900.52 ± 12.27 mg/L), salinity (1.01 ± 0.01 ‰), total hardness (1026.78 ± 5.61 mg/L), sulfate (77.58 ± 0.21 mg/L), and nitrate (58.36 ± 1.47 mg/L). These elevated levels are likely attributable to seawater intrusion, evaporation, and mineral deposits in the region. Thethapola displayed the lowest values for several parameters, including EC (544.05 ± 5.48 µS/cm), TDS (247.85 ± 15.35 mg/L), salinity (0.24 ± 0.02 ‰), total hardness (327.75 ± 2.76 mg/L), chloride (34.95 ± 0.64 mg/L), and sulfate (1.50 ± 0.05 mg/L). This suggest that Thethapola's groundwater is characterized by lower salinity and fresher water quality, possibly due to the area's geological characteristics, and reduced influence of seawater intrusion. Kandakuliya Kudawa exhibited the highest total alkalinity (297.38 ± 23.63 mg/L), indicative of a moderate buffering capacity against pH changes, while Narakkaliya had the lowest total alkalinity (69.33 ± 10.85 mg/L). Additionally, Kandakuliya Kudawa recorded the highest chloride concentration (274.52 ± 4.87 mg/L). Narakkaliya displayed the highest phosphate concentration (1.38 ± 0.01 mg/L) and relatively high salinity, which could be associated with agricultural runoff and fertilizer use in the area. The alkaline conditions (pH > 7) observed in Nawakkaduwa and Narakkaliya, alongside the higher salinity and total hardness in Nawakkaduwa, suggest that groundwater in these areas is more prone to contamination from seawater intrusion and dissolved minerals. Thethapola and Kandakuliya Kudawa, with their slightly acidic to neutral pH and lower salinity, reflect freshwater characteristics with less influence from coastal processes. The study highlights the importance of ongoing monitoring and targeted management to address groundwater quality variations in the Kalpitiya Peninsula, emphasizing the need to understand local hydrogeology and land use for sustainable resource management.Item Assessment of coastal land area changes at Calido beach, Kalutara, using remote sensing and GIS techniques(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Thennakoon, T. M. P. D. U. B.; Fernando, W. S. M.; Randika, R. M. T.; Abinash, R.; Weerasinghe, V. P. A.Calido beach in Kalutara is situated on the western coast of Sri Lanka. It has been severely affected by coastal erosion aggravated by the removal of the sand bar in May 2017. This study aims to assess changes in coastal land area from 2015 to 2021 at two-year intervals utilizing remote sensing and GIS techniques. It focuses on quantifying variations due to sand bar removal and comparing these changes using Landsat 8 OLI images from June in 2015, 2018 and 2021, with 2015 serving as the baseline year. The Normalized Difference Water Index (NDWI), applied to satellite images using ArcGIS software, played a key role in differentiating water and non-water surfaces. NDWI values were reclassified, converted from raster to polygon format, and then smoothened. Subsequently, the non-water surface area for each year was calculated using the geometry tool in ArcGIS software, providing insights into the impact of sand bar removal on coastal morphology. The analysis revealed a minor reduction in the non-water surface area from 4.867 km² in 2015 to 4.865 km² in 2018, which corresponds to a reduction of about 0.04%. By 2021, the non-water surface area increased substantially to 4.966 km², indicating a growth of about 2.08% from 2018 and 2.04% from 2015. The study highlighted the dynamic nature of the coastal land area at Calido Beach, where a slight erosion was noted by 2018, but a substantial increase in non-water surface area was observed by 2021 due to sand deposition after the removal of the sand bar. These findings emphasize the dynamic impact of human interventions on coastal morphology. Recommendations include conducting environmental assessments and developing an integrated coastal management plan to ensure sustainable coastal development and effective management. Additionally, it is crucial to validate these preliminary findings with ground-based measurements to ensure their accuracy and reliability.Item Identification of soil erosion prone areas in Matale district in Sri Lanka using RUSLE model and bare soil index(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Jayasekara, J. M. P. M.; Mendis, C. C. D.; De Silva, K. V. N. T.; Kodikara, K. N.; Weerasinghe, V. P. A.The Matale District is situated in the Central Province of Sri Lanka. It is roughly 1,993 km2 in size and is in the foothills of the central mountain range. Matale District is vulnerable to soil erosion, which causes serious problems for the local environment and agricultural activities. Soil erosion in Matale District is primarily caused by several factors, including rainfall, land use, slope, soil type and conservation practices. This study aims to assess the soil erosion vulnerability in Matale District, Sri Lanka, utilizing the Revised Universal Soil Loss Equation (RUSLE) model and Bare Soil Index (BSI). RUSLE Model, a Digital Elevation Model (15 * 15m), rainfall data, land use and land cover, soil maps, and cropping parameters were used to evaluate the severity of erosion throughout the Matale district. The RUSLE model was calibrated and utilized to determine the rates of soil erosion considering rainfall erosivity, soil erodibility, slope length and steepness, cover management, and conservation practices. Furthermore, the BSI was calculated using remote sensing techniques. The results of the study indicated that soil erosion vulnerability in Matale District varied significantly. The estimated annual average soil loss varied from 0 to 731.71t ha-1 yr-1 . Improved land management practices and forest cover were associated with lower rates of soil erosion, whereas steep slopes, poor vegetation cover, and intense land use practices were associated with higher rates. The BSI map further explains the soil erosion risk map. When comparing the BSI map with the soil erosion risk map, most of the areas with bare soil are prone to erosion. Paddy-cultivated areas, scrub lands, chena and other cultivated areas are prone to experience high levels of soil erosion when considering a land use map. The Red Yellow podzolic soil, Reddish Brown Earths, immature Brown Loams, Erosional remnants steep rock land, and various lithosols soil types are found in areas with severe soil erosion when comparing the soil and Soil Erosion Risk Maps. When comparing a slope map to a soil erosion risk map, areas with a high percentage of slope indicate high soil erosion. Areas with a low percentage of slope on a soil erosion risk map indicate less erosion. Based on the results, recommendations for soil conservation and sustainable land management strategies in the identified vulnerable areas in the Matale district include measures such as afforestation, contour farming, terracing, conservation agriculture practices, and education and awareness programs. This study contributes to understanding soil erosion vulnerability in Matale District and provides a foundation for further research and initiatives focused on sustainable land management and environmental conservation. Proper soil conservation practices should be implemented to safeguard natural resources, improve agricultural productivity, and assure long-term sustainability.Item GIS based multicriteria analysis for flood hazard assessment: A case study from Walawe River basin, Sri Lanka(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Gallage, C. V.; Wijesundera, A. A. S. G.; Kodithuwakku, K. C.; Wickramasingha, W. S. B.; Weerasinghe, V. P. A.Flood hazard mapping has been recognized as a crucial task supporting disaster management efforts. For the study, the lower reach of the Walawe River, which drains the suburbs of the island's southern region, was selected due to its regular flooding. This study used ArcGIS and remote sensing data, and the river basin extent was extracted from satellite images available for the Walawe River, Sri Lanka. Multi-criteria decision analysis (MCDA) was used in this process. The main criteria evaluated are land use, rainfall data, drainage density, elevation, slope, and soil type around the river basin. These criteria are reclassified into five categories depending on the highest to lowest risk of vulnerability to flood. The Analytical Hierarchical Process (AHP) was used to give the weights for the mentioned criteria, and as the outcome, the weighted overlay map (flood hazard map) was obtained and classified under five categories. According to the results, the flood hazard assessment map shows that 25.74% (646.09 km2 ) and 1.92% (48.13km2 ) of the study area was under high or very high hazard levels, respectively, with more populated regions, water bodies, and agricultural land, as well as low-lying flat terrain with lower elevations. The Walawe River basin's lower watershed has high and very high flood-prone areas, while the upper catchment has low and very low flood-prone areas, according to the geographical distribution of the flood hazard map. Low and very low flood hazard zones comprised 18.63% of the total area, whereas moderate flood hazard areas comprised most of the basin. According to the current study, this aims to identify areas within the Walawe River basin that are at risk of flooding, to assess the potential impact of floods on people, property and the environment which support the development of flood risk reduction measures and to provide public awareness.Item Pyrolysis of plastic waste into liquid fuel(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Uthpalani, P. G. I.; De Silva, D. S. M.; Weerasinghe, V. P. A.; Premachandra, J. K.The accumulation of plastic waste in the environment has emerged as a significant global concern. The versatile properties of plastics, such as low weight, low cost and durability which led to their widespread use as substituents for traditional materials like wood, metals, ceramics, and glasses. However, the improper handling and disposal of plastic waste have imposed negative consequences for the environment. The non-biodegradable nature of plastics makes them persist in the environment for extended periods, causing pollution and posing threats to ecosystems. Pyrolysis of plastic waste has been studied extensively in recent years as an effective solution, by exposing the plastic waste to high temperatures in an oxygen-free environment to decompose it into fuel oil, char, and gases. In this study, the waste of four types of plastics samples, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), and a mixture of these three types of plastics, were subjected to pyrolysis. Lab-scale, low-cost pyrolysis system was used to obtain liquid oils and herein, the non-condensed vapor was trapped into an organic solvent. Thermal pyrolysis or non-catalyzed pyrolysis resulted in a liquid yield of 65.64 ± 5.42 – 79.57 ± 1.66 wt.% at a temperature range of 340 – 360 ℃. Considering catalytic activity, high temperature stability, local availability, and abundance, four types of naturally available minerals were selected as potential catalysts for the pyrolysis of waste plastics. The mineral which resulted in the highest liquid yield was identified as the best-performing catalyst and used for further analysis. The catalyzed process resulted in an increased liquid yield of 71.79 ± 0.99 - 80.29 ± 1.76 wt.% at the temperature range of 290 – 320 ℃. The calorific value of the resulting oil in thermal and catalyzed pyrolysis processes were 10,850 -10,961 Kcal/kg and 10,556 - 11,473 Kcal/kg respectively. This reveals that the mineral selected is an ideal catalyst for pyrolysis of plastics and further indicates the quality enhancement of the fuel produced in catalyzed pyrolysis. Further, the fuel quality indicators; calorific values, density, kinematic viscosity, ash content, and water content of the resulting liquid oils under both catalyzed and uncatalyzed/thermal pyrolysis processes were significantly compatible with commercial grade diesel and kerosene fuel oils.Item Soil erosion and sediment yield estimation using GIS-based RUSLE model in Attanagalu Oya watershed, Sri Lanka(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Rathnayaka, W. R. A. J. W.; Weerasinghe, V. P. A.Soil erosion is considered a significant cause of land degradation that negatively impacts natural resources and socioeconomic activities across the globe. Hence, estimating the spatial distribution of soil erosion is essential for making successful policies and implementing proper land conservation and management practices. The present study was designed to estimate the soil erosion and sediment yield in the Attanagalu Oya Watershed, one of the major watersheds located in the low-country wet zone in Sri Lanka, which acts as an important natural ecological zone and a source of surface water for the area. The Revised Universal Soil Loss Equation (RUSLE) model integrated with the Geographic Information System and Remote Sensing was used to quantify soil erosion and map the spatial variation of the soil erosion hazard over a 20-year period. The Sediment Delivery Ratio (SDR) was utilized to estimate the sediment yield generated in the Attanagalu Oya watershed. Land use land cover derived from Landsat 7 ETM and Landsat 8 OLI imagery and Digital Elevation Model (DEM) were integrated into the model. The results indicated that the average annual soil erosion in the Attanagalu Oya watershed has substantially increased from 1.58 t ha-1 yr-1 in 2001 to 2.3 t ha-1 yr-1 in 2020, an increment of about 45.6%. The spatial distribution of soil erosion reflected that the moderate to extremely high erosion levels increased from 2001 to 2020, and the extremely erosion-prone areas (>60 t ha-1 yr-1) were distributed in the eastern part of the watershed. Furthermore, the average annual sediment yield in the Attanagalu Oya watershed was estimated as 0.39 t ha-1 yr-1 with a range of 0 to 124.4 t ha-1 yr-1 in 2001 and 0.57 t ha-1 yr-1 with a range of 0 to 87.4 t ha-1 yr-1 in 2020. The spatial distribution of sediment yield revealed that the high sediment yield was also generated in the eastern part of the watershed as soil erosion. The spatial analysis further revealed that steep slopes (>10.41%), high mean annual rainfall levels (>2500mm), erosion-prone soil types and land use land cover changes, contributed to the high soil erosion and sediment yield in the Attanagalu Oya watershed. The soil erosion hazard information obtained through this study on the Attanagalu Oya watershed can be utilized to design proper erosion conservation and land management practices for improving the sustainability of the watershed.Item Modeling the urban growth and land use changes in Vavuniya, Sri Lanka, using GIS(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Ariyarathna, T. D. S.; Reinurshan, K.; Hazeema, M.; Wickramasinghe, W. S. B.; Weerasinghe, V. P. A.The process of urban growth and its associated land use changes have significant implications for sustainable development and resource management. This research aims to model the urban growth patterns in seven Grama Niladhari (GN) divisions (i.e., Koolankulam, Puthukulam, Paranaddakal, Nachimodai, Omanthai, Maruthanamadu, and Echankulam) in Vavuniya between 2001 to 2021 using Geographical Information Systems (GIS). After obtaining Landsat images covering the study area for the years 2001 and 2021, supervised classification based on a maximum likelihood classifier was applied to the imagery to prepare Land use/Land cover (LULC) maps with four land cover classes: forests, water bodies, croplands, and built-up areas. High-resolution Google Earth images were used as ground truth. Land extents for each LULC type were calculated, and the changes in the area between 2021 and 2001 were compared using ArcGIS 10.8. The change of vegetation indices and water indices were analyzed to find the impact of human activities in the study area. The Normalized Difference Water Index (NDWI) and Normalized Difference Vegetation Index (NDVI) were used for water body analysis and to quantify vegetation, respectively. By using ground truth data, the accuracy assessment was done. The supervised classification indicates that forest cover and the cropland areas decreased (6820.92 ha to 5952.01 ha and 4769.1 ha to 2585.34 ha, respectively) while water bodies and built-up areas increased (633.15 ha to 983.97 ha and 2630.83 ha to 5332.68 ha, respectively). So, the vegetation cover and the water bodies have decreased in 2021. The overall accuracy for the 2021 (land use/ land cover change map) is 0.64 (64%). We envision that the findings of this research will contribute to urban planning and policy-making processes by offering a comprehensive understanding of the past and potential future urban growth dynamics in the studied GN divisions. The results can assist local authorities and stakeholders in making informed decisions regarding land management, infrastructure development, and environmental conservation to ensure sustainable urban growth and resource allocation.