Browsing by Author "Meegahakotuwa, U.S."

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    Rainfall Variations in Kandy District of Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2018) Meegahakotuwa, U.S.; Nianthi, K.W.G.R.
    Rainfall of Sri Lanka is of multiple origins, including monsoonal, convectional and depression. In the rainfall calendar of Sri Lanka, four rainfall seasons have been recognized. They are the First Inter-Monsoon (FIM), South West Monsoon (SWM), Second Inter-Monsoon (SIM) and North East Monsoon (NEM). Rainfall variability over space and time must be regarded as the most significant aspect of the monsoon climate over Sri Lanka. The main objective of this study was to identify the spatial distribution of annual and seasonal rainfall in Kandy District (KD). The monthly rainfall data have been collected from 19 rainfall stations in KD from 2005 to 2014. The data were obtained from the Department of Meteorology and other relevant institutions. Spatial interpolation was done to prepare the isohyet maps for KD using Radial Basis Functions Method in ArcGIS 10.2. The analysis shows that the highest annual average rainfall (5,660 mm) has been recorded at Galamuduna Estate in Dolosbage, and the lowest is recorded at Kundasale (1,594 mm) during the study period. From 2001 to 2014 the Galamuduna annual average rainfall was 5,176 mm. According to the seasonal rainfall, during the FIM period (March-April) the rainfall varies from 700 mm (Craighead Estate) to 241 mm (Minipe). Rainfall during SWM period (May to September) varied from 3,436 mm at Galamuduna to 174 mm at Minipe. The southwestern windward side received the highest rainfall while the Eastern leeward side received the lowest during SWM season. The Galamuduna Estate is situated in highest rainfall region of Wet Zone Up-Country of Sri Lanka. The SIM period (October to November) showed most evenly distributed rainfall over the Kandy District. During the NEM period in December to February, the highest rainfall was recorded in the Eastern side of the KD. The highest rainfall (700 mm-1,000 mm) is recorded in and around Minipe station during this season. Kandy Plateau area received a lower rainfall in the NEM season. The study revealed that the annual and seasonal distribution of rainfall over Kandy District has considerable differences. Based on the annual average rainfall, the wettest place of the Kandy District was the Galamuduna Estate and the driest places were recorded as Kundasale and Minipe. The month of June was recorded as the wettest month (777 mm) in Galamuduna and the same month, Minipe (5 mm) was noticed as the driest during the study period.
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    Seasonal Solar Power Generation Potential for Electricity Supply in the Dry Zone of Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2019-02) Meegahakotuwa, U.S.; Nianthi, K.W.G.R.; Dissanayake, D.M.
    Solar radiation is an important climate element and the largest energy input in the world. Sri Lanka is largely dependent on thermal energy and hydropower for its electricity needs. The solar radiation is the most abundant natural energy and it has great potential to meet the energy requirement of Sri Lanka. Solar-powered photovoltaic (PV) panels convert the sun's rays into electricity by exciting electrons in silicon cells using the photons of light from the sun. Being located close to the equator with the benefit of having sunlight for more than 12 hours per day, using solar systems to generate electricity is truly beneficial for the country. The main objective of this study was to calculate the seasonal solar radiation flux in the Dry Zone of Sri Lanka. The daily solar radiation data was collected by the Silicon Pyranometer for the period from July 2009 to June 2010 from the automatic weather station at Mahailuppallama Agro-Meteorological station. According to the daily average figures, the lowest average daily solar irradiance of 12.6 MJ m-2 was received in the month of December, whereas the highest average daily irradiance of 21.7 MJ m-2 was received in the month of March. According to the seasonal records, the highest solar radiation of 21.4 MJ m-2 received during the First Inter-Monsoon period from March to April and in the South West Monsoon from May to September shows also reasonably high solar radiation of 19.3 MJ m-2, because this period, the airflow generally flows from southwest to northeast direction with less moisture to the Dry Zone. The Second InterMonsoon from October to November, solar radiation was recorded as 17.0 MJ m-2 and in the North East Monsoon period from December to February, the solar radiation was recorded as 16.6 MJ m-2. North East Monson is a climatologically rainy season in the Dry Zone because incoming solar radiation and rainfall are associated with low solar insolation. The study shows that there is a high potential for solar power generation in the Dry Zone of Sri Lanka. The establishment of the solar power plants in the Dry Zone can make a significant contribution to the National Grid of Sri Lanka.
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    Spatial and Temporal Variation of Flood Affected People in Ratnapura District
    (Uva Wellassa University of Sri Lanka, 2018) Bandara, H.M.I.E.; Meegahakotuwa, U.S.; Nilanthi, K.W.G.R.
    The flood is one of the hydro-meteorological disasters frequently occurred in the Ratnapura District. The Ratnapura District has 3275 km2 in land. The highest land cover is occupied by the Kalu Ganga Basin. Kalu Ganga is the second largest river basin in Sri Lanka which receives the high amount of rainfall and volume of river discharge. Due to its hydrological and topographical characteristics, people in the lower plain suffer from frequent floods. The aim of this study is to identify the spatial and temporal variation in relation to People Affected (PA) by Flood in the Ratnapura District. The analysis was mainly based on publicly available data obtained from the Disaster Management Centre (DMC) and District Secretarial Office in Ratnapura for the period from 1987 to 2016. ArcGIS 10.2 techniques were used to create the Choropleth Maps, and the Excel software was used for data analysis and interpretation. A larger number of people are affected in the northwestern quarter of the District and it was high in Ratnapura DSD out of total 17. The other cluster has been identified in Elapatha, Kuruwita, Kiriella, Nivithigala, Pelmadulla and Ayagama DSD. These flood areas are located towards the lower plain in Kalu Ganga Basin and are heavily populated when compared with the other areas of the District. DSDs in the Eastern part of the District have a lower number of PA by flood. 76% of the people have been affected by floods during the southwest monsoon season. The month of May is identified as the peak month in term of PA. This peak has a direct correlation with the climatic seasons in Sri Lanka. The number of people affected by flood in the Ratnapura District has been increased by 137,224 (about 47%) in the recent period of 2002 - 2016 compared to 1987 - 2001. The reason for the increase of PA by Flood in Ratnapura District was identified as the increases of improper land use practices, irrigation management issues, extreme and high intensity of rainfall. This situation will negatively affect the socio-economic condition of the society and water discharge processes of the entire Basin.
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    Spatial and Temporal Variation of Temperature Trends in Last Century of Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2018) Meegahakotuwa, U.S.; Nianthi, K.W.G.R.
    The climate of Sri Lanka is characterized as tropical monsoonal. Temperature is one of the main elements in the tropical climate. Spatial differences observed in air temperature over Sri Lanka are mainly due to altitude, rather than latitude. The mean annual temperatures in Sri Lanka manifest largely homogeneous temperatures in the lowlands and rapidly decrease with altitude towards the Central Highlands. The mean annual temperature varies from 27 °C in the Coastal Lowlands to 16 °C at Nuwaraeliya (1900 m) in the Central Highlands. The objective of this study was to examine the spatial variation of temperature trends of Sri Lanka in the last century. The study was based on mean annual temperature data for the period from 1916 to 2015 at 15 meteorological stations distributed all over the island. The data were obtained from the Department of Meteorology, Colombo. The temperature trends over the last 100-year period were estimated using the Linear Regression analysis. The Mann-Kendall statistical test was applied to identify significant or non-significant monotonic trends. Spatial interpolation was done to prepare the temperature trend map for whole Sri Lanka using Radial Basis Functions Method in ArcGIS 10.2. The results revealed that, the trends of mean annual temperatures have been increasing in all meteorological stations. Out of the 15 stations, 13 displayed statistically significant (P < 0.0001) increasing trends. The rate of the increment annual temperature for the 1916 - 2015 period was in the order of 0.009 °C per year (0.9 °C per century) in Sri Lanka. The highest increasing trends were noticed in and around Anuradhapura, i.e. 0.016 °C per year. Two other increasing trends were noticed in two clusters, one in Nuwaraeliya in the Central Highlands and another in Colombo in Western Coastal Lowlands. Mean annual temperature increment was higher in Dry Zone (0.01 °C per year) than that of the other two zones, i.e. Wet and Intermediate. The trend value of Intermediate Zone was 0.009 °C per year and the Wet Zone value was 0.008 °C per year. Reasons for the increase of temperature in Sri Lanka can possibly be the impact of global warming and the influences from ElNino phenomena. Observed increasing trends of temperature can negatively impact on the human activities and natural environmental processes of Sri Lanka.
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    Variation of Slope Environmental Lapse Rate (SELR) in the Western and Eastern Slopes of the Central Highland in Sri Lanka
    (Uva Wellassa University of Sri Lanka, 2020) Meegahakotuwa, U.S.; Nianthi, K.W.G.R.
    The average temperature decrease (6.5°C km-1 ) with increasing elevation in the free atmosphere is generally called as Environmental Lapse Rate (ELR). The Temperature Lapse Rate (TLR) along the mountain slopes significantly differs from the free atmosphere ELR. The TLR along a mountain slope is here termed as the Slope Environmental Lapse Rate (SELR). The main objective of this study was to identify the variation of the SELR in the Western and Eastern slopes of the Central Highland in Sri Lanka during the South-West Monsoon and North-East Monsoon seasons. The seasonal average temperature has been calculated from 2008 to 2017 from three Meteorological stations; Nuwaraeliya (1895 m), Ratnapura-Western slope station (34 m), and BadullaEastern slope station (670 m). Elevation and temperature of the Nuwaraeliya were taken as the base location and calculated the SELR by ((T1-T2)/(H2-H1) *1000) for Ratnapura and Badulla. The result revealed that the SELR is 5.9°C km-1 in the Western slope and 6.5°C km-1 in the Eastern slope of the Central Highland during the South-West monsoon season. The Western side of Central Highland receives more rainfall than the Eastern side when South-West monsoon occurs. During this season the entire area of Eastern slope in the Central Highland gets dry due to the inverse direction of the monsoon with the effect of orography rainfall. During the North-East monsoon season, the SELR is 6.4°C km-1 in the Western slope and 4.9°C km-1 in the Eastern slope due to the stimulating of NorthEast monsoon on the Eastern side. Considerable spatial differences have been noticed during two seasons. The seasonal monsoon rainfall patterns are highly affected for variation of the Slope Environmental Lapse Rate in the Western and Eastern slopes of the Central Highland in Sri Lanka. . Keywords: Central Highland, Eastern slope, Seasons, Slope Environmental Lapse Rate, Western Slope