Browsing by Author "Weerasinghe, V. P. A."

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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.
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.
Assessment of spatial variation of ground water quality in Colombo district, Sri Lanka
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Antalyn, B.; Weerasinghe, V. P. A.
In Sri Lanka, groundwater resources are widely used for domestic, commercial and industrial purposes and the demand for ground water is steadily increasing, particularly for urban & rural domestic water supplies, irrigated agriculture and in the industrial sector. This rapid increase in demand and lack of management is exerting considerable pressure on the available groundwater resources. Therefore, it’s vital to monitor the quality of ground water for sustainable utilization. For ground water quality assessment, Colombo district was selected as the study area since it is urbanized rapidly in last decades. The main aim of the study was assessing spatial variation of ground water quality in Colombo district in year 2018. Some of the physicochemical parameters were selected namely pH, temperature, conductivity, total dissolved solids, salinity, COD, hardness, total phosphate, nitrate-N, DO and BOD5. Sampling was carried out during the south western monsoon from June 2018 to September 2018. With the availability 03 open wells were selected randomly, from each Divisional Secretary Division (DSD) and water samples were collected during the morning hours in between 0-3 m depths as 03 replicates from each well at once. Total 39 open well samples were tested using standard methods. The obtained results are compared with proposed ambient water quality standards for inland waters in Sri Lanka by the Central Environmental Authority (CEA). The results reveal that in most of the sites pH, COD and BOD5 are not meeting the standards. Lower pH levels can occur due to natural acidification as well as anthropogenic causes linked to the industrialization, atmospheric emissions or cultivation. Results of PCA analysis reveal that the sites which are surrounded with agricultural areas such as in Hanwella, Padukka, Homagama, Kaduwela, and Kesbewa showed higher nitrate-N, total phosphate levels and low pH values. In contrast higher pH values as well as low nitrate-N and total phosphate levels were observed in non-agricultural areas. Hence come to a conclusion that long-term agricultural practices may have acidified the ground water and elevated organic matter accumulation due to high urban runoff, sewage seepage from slums and poor maintenance of wells could have caused higher COD, BOD5 levels in urbanized areas such as in Thimbirigasyaya, Moratuwa, Dehiwala, and Kotte. The study of physicochemical characteristics of this ground water samples suggests that the evaluation of water quality parameters as well as water quality management practices should be carried out to protect the water resources. Unless the use of surface area is managed in a sustainable way, it will have adverse repercussions on the environment
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.
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.
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.
A geo-spatial analysis of dengue patients and rainfall in Sri Lanka -2017
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Pathiraja, K.; Premadasa, S.; Gnanasinghe, S.; Wadasinghe, L. G. Y. J. G.; Weerasinghe, V. P. A.
Dengue is one of the most prevalent arthropod borne virus affecting human. There are four serotypes that manifest with similar symptoms and two main vectors identified in Sri Lanka named as Aedes aegypti and Aedes albopictus. Dengue disease range from mild to dengue hemorrhagic fever. The distribution of dengue vector is varied mostly according to the rainfall. This study evaluates the relationship between percentage dengue patients in each district of Sri Lanka and monthly average rainfall distribution in 2017. Data was analyzed using ArcGIS 10.2 software. In order to get descriptive results, spatial autocorrelation (Moran’s I) was carried out. Positive Moran’s I shows that the average rainfall data are clustered according to the climatic zones in Sri Lanka and percentage dengue patients’ data for February, March, May, June, July and August months are clustered. Hot Spot Analysis was carried out for the clustered months for dengue patients. According to the Hot Spot Analysis the average rainfall distribution of each month of 2017 in Sri Lanka is restricted to specific districts; Hot spots are, Ampara (February), Rathnapura (May, June, July), Rathnapura and Kaluthara (September), Kaluthara (October) and Badulla (December) (99% confidence). Similarly, percentage dengue patients’ distribution in 2017 is restricted to specific districts; Hot spots are Trincomalee (February) and Colombo (March) (99% confidence). Ordinary Least Squares (OLS) linear regression was carried out to identify the relationship between the percentage dengue patients and monthly average rainfall. The variable distributions and relationships graphs of each month indicate a positive relationship between average rainfall and percentage dengue patients. Adjusted R2 in the diagnostic output of each month range between 0.7785 (June) and 0.1674 (February) and indicates that 16.74% - 77.85% of the variation in percentage dengue patients can be explained by average rainfall in 2017. It shows that only rainfall cannot explain the total percentage of dengue patients and that there are other environmental parameters which may contribute. There is a relationship between the percentage of dengue patients in each district and average rainfall distribution which appears to vary. Therefore, further studies should be carried out to identify other environmental parameters on the distribution of dengue such as atmospheric temperature, humidity, wind velocity, intensive farming, urbanization and solid waste disposal practices etc. Using multiple regression, multicollinearity between independent variables can be estimated using Geo statistics. Using environmental parameters, an environmental dengue index can be developed to further relate it with dengue patients’ percentage for geo-spatial analysis to develop a model for incidence of dengue in each district in Sri Lanka with varying environmental variables.
GIS as a tool to find the suitable place for construction of water tanks in Karuwalabadda, Puttalam District, Sri Lanka
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Vaigunthan, T.; Lansakara, L. M. A. P.; Weerasinghe, V. P. A.
The United Nations has long been addressing the global water crisis caused by insufficient water supply to satisfy basic human needs and growing demands on the world's water resources to meet human, commercial and agricultural needs. Although there are lots of water bodies in Sri Lanka some parts of the country suffer with a severe water crisis. Karuwalabadda is a Grama Niladari Division (GND) in Puttalam district in Sri Lanka which has 135 houses and more than 245 families and there are no any surface water bodies observed in the area. The most considerable problem in that area is the lack of drinking water due to longer period of drought except 4 -5 months. Many organizations and students from different universities tried to help them as short term solutions by distributing water in bowsers and bottles. There were several drawbacks of these solutions such as water distribution coverage is changing, water distribution does not occur throughout the day, higher fuel waste for water bowsers, there is no specific route for distribution of water and plastic bottles make environmental problem etc. Hence previous solutions are not sustainable, it is proposed to construct tanks permanently in different locations of the area. The suitable locations to construct water tanks were found out using ArcGIS software for the construction of tanks with minimum environmental impacts. From the GND map of Sri Lanka, Karuwalabadda study area was extracted and digitized with houses and main roads. Buffer was done 500m away from houses and 75m away from roads and then reclassified. Land use map of Karuwalabadda was converted from vector to raster. Surface water layer was not considered because there are no any surface water body in Karuwalabadda GND. Criteria for the suitable locations were bare land, 500 m away from houses and 75 m away from main roads. The final suitable area to construct water tanks map was prepared by assigning weightage to different thematic maps as 60% to land use map, 20% to houses and 20% to roads and then they were superimposed by weighted overlay tool. Final map was classified into 03 classes as suitable, moderately suitable and not suitable area. From suitable area 07 locations were selected to construct the water tanks. It was observed that constructing seven tanks of capacity 3000 L in the selected areas the water need of the whole village can be fulfilled. Proposed number of families for one tank can be approximately 22 families. Society based maintenance can be an effective way to maintain these tanks and by handing over these tanks to Preadeshiya Sabha water can be filled once a week. GIS technology is an effective and efficient tool for solving any location based environmental problems in the world and it has more potential to be used further to overcome many environmental challenges.
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.
The Holt-Winters’ method for forecasting water discharge in Attanagalu Oya
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Anuruddhika, M. L. P.; Premarathna, L. P. N. D; Perera, K. K. K. R.; Hansameenu, W. P. T.; Weerasinghe, V. P. A.
Forecasting river water discharge is significant in developing flood and agriculture management plans. Annual flood events damage properties, agricultural field, and infrastructures, etc. can be observed in Attanagalu Oya catchment area in Sri Lanka. Therefore, the aim of this study is to forecast water discharge rates (m3/s) at the Dunamale gauging station of Attanagalu Oya using Holt-Winter's method. Holt-Winter's method was chosen because of its’ ability to model trend and seasonal fluctuations, less data requirements and simplicity. Time series models were fitted using the Holt-Winter's method to daily water discharge rates for the period of 2015 –2019 and water discharge was forecasted for the year 2020. The accuracy of the fitted time series models was tested using root mean squares error (RMSE) and mean absolute error (MAE) values. Results showed that the additive Holt-Winters’ method is more appropriate for future forecasting which gave the minimum RMSE and MAE values. Forecasted results will be useful to identify future flood events in advanced to take necessary actions to mitigate damages.
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.
Identification of suitable areas to cultivate Aloe vera in Kegalle District, Sri Lanka using GIS
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Dissanayake, C. T. M.; Weerasinghe, V. P. A.
Aloe vera (Aloe barbadensis Miller) is used in ayurvedic medicine, pharmaceuticals, cosmetic products and also as a food product such as drinks or mixer with yoghurt. It is getting popular with the improvements in technology of harvesting and processing the product. In Sri Lanka, it is popular as a home garden crop, but not as a crop growing in large-scale. Most Sri Lankans are less aware of getting an income from Aloe vera. Therefore, the aim of this study is to make Aloe vera cultivation popular by identifying suitable areas to cultivate Aloe vera in Kegalle district, which was the study area of this research. Data analysis was done by using ArcGIS software tools to select the suitable areas. The criteria to grow Aloe vera successfully were selected using relevant literature. They were namely land uses such as coconut or bare lands, annual rainfall range as 1800 mm-2300 mm and annual temperature range as 25 °C - 26 °C. Those criteria were considered as most favorable factors to grow Aloe vera successfully with demanding leaf thicknesses. Land use data was collected from the Survey Department, Colombo and rainfall and temperature data were collected from the Meteorology Department, Colombo. Rainfall and temperature layers were developed by using Kriging interpolation technique in spatial geostatistics in ArcGIS software. Then land use layer, rainfall layer and temperature layer were overlaid using spatial analysis tools to identify the most suitable area, moderately suitable areas and not suitable areas. Kelegama and Rambukkana DSD areas are the most suitable areas to grow Aloe vera in Kegalle district. The final map generated from this study will be useful for extension/field officers of the Department of Agriculture, to enhance the awareness of people in Kegalle district about suitable places to grow Aloe vera in order to get an extra income as well as to get the maximum utility of the land.
Identify a potential location for wind power plant in Jaffna district, Sri Lanka using GIS techniques
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Weerasinghe, V. P. A.; Dilshara, R. M. P.; Liyanage, P. M.; Perera, G. L. D. N.
Wind energy is one of the renewable energy sources in the Sri Lanka. Currently, there are some active wind power stations located in Central region, Hambanthota, and Puttalam. National Renewable Energy Laboratory (NREL) estimates that there are nearly 5000 km2 of windy areas with good-to-excellent wind resource potential in Sri Lanka after accounting for excluded lands like national parks, nature reserves, archaeological and cultural sites. The windy land represents about 6 % of the total land area (65,600 km2) of Sri Lanka. Hence the population increment has become a major problem on electricity demand and the hydro power is limited especially in dry season, this study is focused on finding a suitable location to establish a wind power plant in Jaffna District using Geographical Information Systems (GIS). The land was selected considering criteria namely; the distance from obstructions as 150 m, the distance from Coastal area as 100 m, the height from buildings and trees as 9 m and 1.5 acres of land area was considered as providing 2 MW of power. The land use maps were collected from Survey Department, Sri Lanka and the wind data was taken using wind finder software. Under the methodology, the wind speed data of selected points were clipped to Jaffna district map. The wind speed, land use, terrain, building area and nature reserve maps were reclassified and assigned weights using weighted overlay tool in ArcGIS software to derive the suitability map. The weights were given as wind speed (70%), land use (15%), building area (10%), nature reserves (4%) and terrain (1%). According to the results shown in the map, the wind speed was high in Delft Island and Nainatheeve and poor in Chundikulam. When considering all the criteria, Delft island (5000 ha) should be the best place and the land area of 200 ha can be used for the construction of the wind power station
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.
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.
Plastic waste management strategies in Sri Lanka: Kandy and Colombo municipalities
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Gunasekera, K. R; Dissanayake, D. P. M. H. S; Dilrukshi, G. A. H. T; Dissanayake, J. A.; Sandanisha, L. G. S.; Weerasinghe, V. P. A.
Plastic waste is a growing issue in Sri Lanka and has much room for improved management strategies. To implement proper plastic waste management, it is important to identify the plastic content present in a waste sample, the composition of plastic waste types and people’s perspectives on this. This study was aimed to analyze plastic waste composition at household level and municipal level as well as to select suitable plastic waste sorting techniques for different plastic waste management strategies. Data were collected from the Kandy (KMC) and Colombo (CMC) municipalities to analyze people’s perspectives on plastic disposal practices and to investigate the different plastic types (Polyethylene Terephthalate (PET), High Density Polyethylene (HDPE), Polyvinyl Chloride (PVC), Low Density Polyethylene (LDPE), Polypropylene (PP), Polystyrene (PS) and other) included in a plastic waste sample. Based on the responses of the selected households, KMC waste collection service was more satisfactory in comparison to the CMC. The most abundantly used plastic types in household level were LDPE, PET and PS while the plastic types in a plastic waste sample analyzed at the waste collection sites of the municipalities showed similar abundance. A SWOT analysis was conducted on a selected set of plastic waste sorting techniques; manual sorting, density separation, air classification, electrostatic separation and sensor-based sorting. A questionnaire survey based on increased number of households in KMC and CMC is necessary to get the people’s perspective precisely. Plastic waste composition at the household as well as municipal level should be investigated weekly or monthly to get the temporal variation of plastic waste generation.
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.
Pyrolysis of waste polypropylene to fuel oil
(Chemistry in Sri Lanka, 2022) Uthpalani, P. G. I.; Premachandra, J. K.; Weerasinghe, V. P. A.; De Silva, D. S. M.
Plastic waste accumulation in the environment has increased rapidly. This is mainly due to their versatile properties, which allow them to be used as substitutes for wood, metals, ceramics, and glass. They have diverse applications, as they are light-weight, durable, cost-effective, and stable products. However, the world is experiencing the adverse effects of plastic debris in the environment due to plastic waste mismanagement. Pyrolysis of plastic has been identified as an effective method of plastic waste management by converting the waste into fuel oil, char, and gases. The pyrolysis of waste polypropylene (PP) using a low-cost, simple lab-scale apparatus in the presence and absence of catalysts is discussed here. In the current research, the efficiency of the catalyst, Zeolite Socony Mobil-5 (ZSM- 5), in pyrolysis process was investigated. The generated volatile products were condensed into resultant liquid oil. Active carbon filters and organic solvents were used to trap the non-condensed gas fraction to prevent possible atmospheric pollution. The non-catalyzed pyrolysis of PP resulted a high liquid yield of 79.57 ± 1.66 wt. % with a low gaseous yield (14.64 ± 0.84 wt. %) at 330 °C while the ZSM-5 catalyzed process reduced the liquid yield to 56.88 ± 2.29 wt. % and increased the gaseous yield (38.13 ± 1.88 wt. %) at 280 °C. Then resultant liquids were fractionated based on the boiling points of several petroleum fractions (naphtha, kerosene, and diesel) and each fraction was analyzed by GC-MS to identify the constituent compounds. Accordingly, the non- catalyzed pyrolysis produced 3,3,5-trimethyl-heptane (C10H22), 4-methyl-2-undecene (C12H24), 1-dodecene (C12H24), and 2-methyl-1-hexadecanol (C17H36O) while the catalyzed pyrolysis with the ZSM-5 resulted 1-ethyl- 2-methyl-benzene (C9H12), 3,3,5-trimethyl-heptane (C10H22), (Cyclopentylmethyl)-cyclohexane (C12H22), and n-Nonylcyclohexane (C15H30) as the major constituents.
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.
Spatial analysis of population density, birth rate and death rate in Sri Lanka (2015 and 2016)
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Rajapaksha, D.; Jayakody, H.; Wadasinghe, L. G. Y. J. G.; Gnanasinghe, S.; Weerasinghe, V. P. A.
Lack of open space, shortage of clean water, and pollution are major concerns of higher population densities. In 2015, United Nations (UN) identified 17 Sustainable Development Goals (SDG) expected to fulfill by 2030 with the help of the governments of countries, which many researches reveals to lower the population growth. This study aims to analyze the distribution pattern of population density in Sri Lanka. Population density depends on resource, natural growth of population and migration. In this study, spatial pattern of population density, birth rate and death rates in Sri Lanka were analyzed for 2015 and 2016. The spatial relationships of population density with birth and death rate of 25 districts were also analyzed. The population data were collected from Department of Census and Statistics of Sri Lanka and analyzed using Geo-statistics tools in ArcGIS 10.2. Spatial patterns and relationships among the data sets were identified. Spatial Autocorrelation (Moran’s I) was carried out for population density, birth and death rate for the 25 districts. Spatial pattern of population density is highly clustered (p=0.001, Moran’s I: 0.198) while spatial pattern of birth rates of each district is randomly distributed in 2015 and 2016. High population density restricted areas are Colombo and Gampaha (99% and 90% CI) for both years. Death rates of districts are slightly clustered in 2015 (p=0.035, Moran’s I: 0.198) and 2016 (p=0.022, Moran’s I: 0.218). Hot Spot Analysis tool was used to identify the clustered areas. High death rate prevailing districts are Colombo (95% CI), Kandy and Galle (90% CI) in 2015. Low death rate prevailing district is Killinochchi (90% CI). In 2016, high death rate is observed in Colombo (99% CI) and Jaffna districts (90% CI). Spatial relationship was identified by using Ordinary Least Squares (OLS) tool. 44.25% of the population density variation can be explained by death rate (adjusted R2=0.4425) in 2015 and, 49.96% can be explained by death rate (adjusted R2=0.4996) in 2016. Regression equation can be developed according to the coefficient output (p<0.05) in 2015 and 2016. There is a significant relationship between death rate and population density (p=0.00017) in 2015 and 2016. The overall results of the present study can be used for planning development projects in the country to fulfill the SDG of UN. Colombo and Gampaha districts should have projects leading to decrease the population density. Colombo and Jaffna districts need to decrease death rates by improving their living standards with better health facilities. This study has to continue with emigration and immigration rate data to develop a better model for population density in the country.