Jagath Gunatilake | University of Peradeniya (original) (raw)

Papers by Jagath Gunatilake

V International Symposium on Pistachios and Almonds, 2011

Journal of Tea Science, 2012

Vingnanam Journal of Science, Jan 30, 2017

Groundwater is one of earth's most vital renewable and /or non-renewable and widely distributed r... more Groundwater is one of earth's most vital renewable and /or non-renewable and widely distributed resources as well as an important source of water supply throughout the world. The quality of water is a vital concern for mankind since it is directly linked with human welfare. The groundwater is believed to be comparatively much clean and free from pollution than surface water. Groundwater can become contaminated naturally or because of numerous types of human activities; residential, municipal, commercial, industrial, and agricultural activities can all affect groundwater quality (Balakrishnan, 2011).

BMC Public Health, May 26, 2021

Background: Physical Activity (PA) promotes health and wellbeing and walking is one of the easies... more Background: Physical Activity (PA) promotes health and wellbeing and walking is one of the easiest and commonest way to incorporate activity into everyday life. This study examined the association between the objectively measured neighbourhood physical environment and walking among the adults in Colombo Municipal Council (CMC) area in Sri Lanka. Methods: A cross sectional study was carried out and primary data collection carried out to assess walking, sociodemographic characteristics and geo location of residence. Secondary data was obtained to assess neighbourhood environment from existing spatially referenced data from the survey department of Sri Lanka. Geographic Information Systems (GIS) was used to calculate density measures (residential density, land use, connectivity and access) and distance measures, which were then correlated with walking. Results: A sample consisted of 284 adults aged 29-59 years with a mean age of 40.6 (SD,10.9) years. The total mean minutes walked a week was 175.8 min with a standard deviation of 214.0. The mean and the standard deviations of walking per week for transportation and leisure were 158.4 (SD,196.6) and 17.5 (SD,70.1) respectively. Residential density measures, building foot print area, length of major roads, number of intersections, number of bus stops, and distance to nearest major roads showed significant moderate degree of correlations with total minutes of walked per week, (p < 0.001). These results were similar with walking for transportation. Conclusion: There is indication that neighbourhood features are associated with walking among the adults in the CMC area using secondary data on physical environment. This paves way for further exploration to understand the relationship between neighbourhood physical environment and walking which could be used for effective interventions to promote walking.

Municipal solid waste (MSW) management and final disposal is one of the critical issues face by L... more Municipal solid waste (MSW) management and final disposal is one of the critical issues face by Local Authorities in Sri Lanka. Gohagoda, Kandy situated at Central Province of Sri Lanka, is one of the disposal sites, which has been used since 1960s for open dumping of municipal solid wastes with no treatment process in operation. Open dumping of solid wastes can cause detrimental impacts to groundwater, surface water, soil and air. Therefore, a proper landfill design and leachate treatment system is utmost important to prevent such impacts. This research was carried out to investigate water quality around Gohagoda dumping site and to design an economical leachate treatment system by estimating quality and quantity of leachate. Using bore holes, shallow wells and drains, water sampling was carried out over 34 locations of the study area. GPS was used to position sampling locations. Timely variation of the water quality parameters such as BOD, COD, NO3 , NO2 , PO4 3, Na, K, Ca, DO, conductivity, pH and selected heavy metals of leachate, surface and ground water were measured at the surrounding area of the dumping site relate to weather conditions. Flow of leachate was measured during rainfalls and total flow was obtained using runoff model. The analysis of water quality parameters showed that the surface water and groundwater around the dump site are highly contaminated. In addition, the results envisaged that the cause of contamination of water is the leachate of dumping site and consequently, leachate treatment is very essential to minimize the contamination of surface and ground water at surrounding area. Hence, a suitable hydraulic design for leachate treatment was introduced to reduce concentration of pollutants below the permissible levels. The propose treatment system consists of three principal unit processes such as biological treatment, activated carbon absorption unit followed by a construction wetland.

Background: Physical Activity (PA) plays an important role for health. Walking is the easiest way... more Background: Physical Activity (PA) plays an important role for health. Walking is the easiest way to incorporate activity into everyday life. However, few adults achieve the recommended levels of activity. This study examined the association of the objectively measured neighbourhood physical environment with walking among the adults in Colombo, Sri Lanka through a cross sectional design. Methods : Primary data collection was carried out to assess the minutes walked, socio-demographic characteristics and geo location of residence. Secondary data was obtained to assess neighbourhood environment from existing spatially referenced data. Geographic Information Systems (GIS) was used to calculate density measures (residential density, land use, connectivity and access) and distance measures. Results: A sample consisted of 284 adults aged 29-59 years (mean age 40.6 (SD-10.9) years, Female: 56%). Adults reported a mean of 175.8 (SD214.0) minutes/week of total walking out of which, 158.4 (SD...

Parasites & Vectors, 2021

Background Spatial and temporal changes in the dengue incidence are associated with multiple fact... more Background Spatial and temporal changes in the dengue incidence are associated with multiple factors, such as climate, immunity among a population against dengue viruses (DENV), circulating DENV serotypes and vertical transmission (VT) of DENV in an area at a given time. The level of VT in a specific location has epidemiological implications in terms of viral maintenance in vectors. Identification of the circulating DENV serotypes in both patients and Aedes mosquito larvae in an area may be useful for the early detection of outbreaks. We report here the results of a prospective descriptive study that was conducted to detect the levels of VT in Aedes mosquito larvae and circulating DENV serotypes in patients and Aedes mosquito larvae from December 2015 to March 2017 in an area of Sri Lanka at high risk for dengue. Methods A total of 200 patients with clinically suspected dengue who had been admitted to a tertiary care hospital during a dengue outbreak (3 study periods: December 2015–...

In the recent past, Sri Lanka has been experiencing an increase of intensity and frequency of nat... more In the recent past, Sri Lanka has been experiencing an increase of intensity and frequency of natural disasters. Therefore, the study was carried out to introduce an Open Source application to collect the field level information and to identify the flood inundation areas through a 3D model. The case study area included 48 Grama Niladhari Divisions in Manmunai North Divisional Secretariat (DS), Batticaloa District, Sri Lanka. The study helped to analyze the role of OpenStreetMap (OSM) to support the mapping of the flood risk level of the study area. This objective was achieved by collecting flood exposure data through community participatory method using OSM, which was integrated into a Digital Elevation Model (DEM). Elevation points were collected using Google Earth and TCX Converter. The flood hazard maps were created using inputs such as water depth and flood extent of the DEM and verified through a local community participatory mapping exercise. Next, vulnerability maps were gene...

Ceylon Journal of Science, 2017

Landslides are the most recurrent and prominent natural hazard in many areas of the world which c... more Landslides are the most recurrent and prominent natural hazard in many areas of the world which cause significant loss of life and damage to properties. By generating landslide susceptibility maps, the hazard zones can be identified in order to produce an early warning system to reduce the damage. In this study, the predictive abilities of two statistical models, Logistic regression (LR) model and Geographically Weighted logistic regression (GWLR) model, were compared. As a case study, a data set collected for nine relevant causative factors over the period from 1986 to 2014 was taken from Badulla district, Sri Lanka, which is highly affected by landslides. The performance of each model was tested by using the Area under the curve (AUC) value of Receiver operating characteristic curve (ROC), and the GWLR model was selected as the best fitted model. The probabilities obtained for each pixel in the study area using the selected model were classified into three classes (Low, Medium and High) based on standard deviation method in GIS software. Finally, a landslide susceptibility map was generated related to the above three classes, from which high risk areas can be identified to take necessary actions.

Journal of the Geological Society of Sri Lanka, Feb 28, 2019

The qualitative evaluation of large databases and determination of significance of multivariate d... more The qualitative evaluation of large databases and determination of significance of multivariate databases is a prominent approach. Numerical methodologies of data evaluation has yet to uncover many exciting opportunities for application in disaster management. The evaluation of landslide susceptibility usually deals with various combinations of geographical data sets including slope forms, catchment hydrology, stream hydrology, precipitation potential or rainstorm, soil saturation, soil strength, saturation potential and various derived forms of geological data. The difficulties associated with introducing a large data integrated system are first, having a systematic evaluation methodology which is practical, and second, having a set of scientific auxiliary decision methods to evaluate total significance. The Analytical Hierarchical Process (AHP) is a convenient way for quantitative analysis in decision making under a probabilistic environment and it is also an effective method for scientists to objectively provide subjective judgment. The AHP improves qualitative approaches on mutually exclusive dependencies or interdependencies of data and evaluates the significance in the Weighted Average Analysis (WAA) approach on landslide susceptibility. This qualitative approach will be further used to calibrate the large databases on landslide susceptibility evaluation with more and more interacting sets of data. The overall accuracy of the WAA model approach always depends on the sensitivity of the GIS databases and calibration through physically known datasets of landslide occurrences.

Ceylon Journal of Science, 2018

A light loving invasive shrub, Austroeupatorium inulifolium has been spreading many land use type... more A light loving invasive shrub, Austroeupatorium inulifolium has been spreading many land use types in the Knuckles Forest Reserve (KFR) in Sri Lanka, including man-made grasslands. In developing countries, there are limitations of using novel technologies to quantify and track the distribution of invasive species due to high costs and lack of facilities. This is a setback for their early detection and to introduce effective control measures. This pilot study attempted to map the distribution of A. inulifolium in man-made grasslands in KFR using high spatial multispectral images. Unsupervised, supervised and knowledge-based classifications were performed to quantify the spatial distribution of A. inulifolium in ERDAS Imagine. The results generated comparable results of the extent of area under A. inulifolium by using the unsupervised (108 ha), supervised (94 ha) and knowledge-based classifications (93 ha). They were 18, 15 and 15% from the total area selected for the study (622-646 ha), respectively. The results indicated the suitability of high spatial multispectral imageries in quantifying the spatial distribution of A. inulifolium. Further studies are recommended to investigate long-term changes in invasive plant population using multi temporal satellite data.

V International Symposium on Pistachios and Almonds, 2011

Journal of Tea Science, 2012

Vingnanam Journal of Science, Jan 30, 2017

Groundwater is one of earth's most vital renewable and /or non-renewable and widely distributed r... more Groundwater is one of earth's most vital renewable and /or non-renewable and widely distributed resources as well as an important source of water supply throughout the world. The quality of water is a vital concern for mankind since it is directly linked with human welfare. The groundwater is believed to be comparatively much clean and free from pollution than surface water. Groundwater can become contaminated naturally or because of numerous types of human activities; residential, municipal, commercial, industrial, and agricultural activities can all affect groundwater quality (Balakrishnan, 2011).

BMC Public Health, May 26, 2021

Background: Physical Activity (PA) promotes health and wellbeing and walking is one of the easies... more Background: Physical Activity (PA) promotes health and wellbeing and walking is one of the easiest and commonest way to incorporate activity into everyday life. This study examined the association between the objectively measured neighbourhood physical environment and walking among the adults in Colombo Municipal Council (CMC) area in Sri Lanka. Methods: A cross sectional study was carried out and primary data collection carried out to assess walking, sociodemographic characteristics and geo location of residence. Secondary data was obtained to assess neighbourhood environment from existing spatially referenced data from the survey department of Sri Lanka. Geographic Information Systems (GIS) was used to calculate density measures (residential density, land use, connectivity and access) and distance measures, which were then correlated with walking. Results: A sample consisted of 284 adults aged 29-59 years with a mean age of 40.6 (SD,10.9) years. The total mean minutes walked a week was 175.8 min with a standard deviation of 214.0. The mean and the standard deviations of walking per week for transportation and leisure were 158.4 (SD,196.6) and 17.5 (SD,70.1) respectively. Residential density measures, building foot print area, length of major roads, number of intersections, number of bus stops, and distance to nearest major roads showed significant moderate degree of correlations with total minutes of walked per week, (p < 0.001). These results were similar with walking for transportation. Conclusion: There is indication that neighbourhood features are associated with walking among the adults in the CMC area using secondary data on physical environment. This paves way for further exploration to understand the relationship between neighbourhood physical environment and walking which could be used for effective interventions to promote walking.

Municipal solid waste (MSW) management and final disposal is one of the critical issues face by L... more Municipal solid waste (MSW) management and final disposal is one of the critical issues face by Local Authorities in Sri Lanka. Gohagoda, Kandy situated at Central Province of Sri Lanka, is one of the disposal sites, which has been used since 1960s for open dumping of municipal solid wastes with no treatment process in operation. Open dumping of solid wastes can cause detrimental impacts to groundwater, surface water, soil and air. Therefore, a proper landfill design and leachate treatment system is utmost important to prevent such impacts. This research was carried out to investigate water quality around Gohagoda dumping site and to design an economical leachate treatment system by estimating quality and quantity of leachate. Using bore holes, shallow wells and drains, water sampling was carried out over 34 locations of the study area. GPS was used to position sampling locations. Timely variation of the water quality parameters such as BOD, COD, NO3 , NO2 , PO4 3, Na, K, Ca, DO, conductivity, pH and selected heavy metals of leachate, surface and ground water were measured at the surrounding area of the dumping site relate to weather conditions. Flow of leachate was measured during rainfalls and total flow was obtained using runoff model. The analysis of water quality parameters showed that the surface water and groundwater around the dump site are highly contaminated. In addition, the results envisaged that the cause of contamination of water is the leachate of dumping site and consequently, leachate treatment is very essential to minimize the contamination of surface and ground water at surrounding area. Hence, a suitable hydraulic design for leachate treatment was introduced to reduce concentration of pollutants below the permissible levels. The propose treatment system consists of three principal unit processes such as biological treatment, activated carbon absorption unit followed by a construction wetland.

Background: Physical Activity (PA) plays an important role for health. Walking is the easiest way... more Background: Physical Activity (PA) plays an important role for health. Walking is the easiest way to incorporate activity into everyday life. However, few adults achieve the recommended levels of activity. This study examined the association of the objectively measured neighbourhood physical environment with walking among the adults in Colombo, Sri Lanka through a cross sectional design. Methods : Primary data collection was carried out to assess the minutes walked, socio-demographic characteristics and geo location of residence. Secondary data was obtained to assess neighbourhood environment from existing spatially referenced data. Geographic Information Systems (GIS) was used to calculate density measures (residential density, land use, connectivity and access) and distance measures. Results: A sample consisted of 284 adults aged 29-59 years (mean age 40.6 (SD-10.9) years, Female: 56%). Adults reported a mean of 175.8 (SD214.0) minutes/week of total walking out of which, 158.4 (SD...

Parasites & Vectors, 2021

Background Spatial and temporal changes in the dengue incidence are associated with multiple fact... more Background Spatial and temporal changes in the dengue incidence are associated with multiple factors, such as climate, immunity among a population against dengue viruses (DENV), circulating DENV serotypes and vertical transmission (VT) of DENV in an area at a given time. The level of VT in a specific location has epidemiological implications in terms of viral maintenance in vectors. Identification of the circulating DENV serotypes in both patients and Aedes mosquito larvae in an area may be useful for the early detection of outbreaks. We report here the results of a prospective descriptive study that was conducted to detect the levels of VT in Aedes mosquito larvae and circulating DENV serotypes in patients and Aedes mosquito larvae from December 2015 to March 2017 in an area of Sri Lanka at high risk for dengue. Methods A total of 200 patients with clinically suspected dengue who had been admitted to a tertiary care hospital during a dengue outbreak (3 study periods: December 2015–...

In the recent past, Sri Lanka has been experiencing an increase of intensity and frequency of nat... more In the recent past, Sri Lanka has been experiencing an increase of intensity and frequency of natural disasters. Therefore, the study was carried out to introduce an Open Source application to collect the field level information and to identify the flood inundation areas through a 3D model. The case study area included 48 Grama Niladhari Divisions in Manmunai North Divisional Secretariat (DS), Batticaloa District, Sri Lanka. The study helped to analyze the role of OpenStreetMap (OSM) to support the mapping of the flood risk level of the study area. This objective was achieved by collecting flood exposure data through community participatory method using OSM, which was integrated into a Digital Elevation Model (DEM). Elevation points were collected using Google Earth and TCX Converter. The flood hazard maps were created using inputs such as water depth and flood extent of the DEM and verified through a local community participatory mapping exercise. Next, vulnerability maps were gene...

Ceylon Journal of Science, 2017

Landslides are the most recurrent and prominent natural hazard in many areas of the world which c... more Landslides are the most recurrent and prominent natural hazard in many areas of the world which cause significant loss of life and damage to properties. By generating landslide susceptibility maps, the hazard zones can be identified in order to produce an early warning system to reduce the damage. In this study, the predictive abilities of two statistical models, Logistic regression (LR) model and Geographically Weighted logistic regression (GWLR) model, were compared. As a case study, a data set collected for nine relevant causative factors over the period from 1986 to 2014 was taken from Badulla district, Sri Lanka, which is highly affected by landslides. The performance of each model was tested by using the Area under the curve (AUC) value of Receiver operating characteristic curve (ROC), and the GWLR model was selected as the best fitted model. The probabilities obtained for each pixel in the study area using the selected model were classified into three classes (Low, Medium and High) based on standard deviation method in GIS software. Finally, a landslide susceptibility map was generated related to the above three classes, from which high risk areas can be identified to take necessary actions.

Journal of the Geological Society of Sri Lanka, Feb 28, 2019

The qualitative evaluation of large databases and determination of significance of multivariate d... more The qualitative evaluation of large databases and determination of significance of multivariate databases is a prominent approach. Numerical methodologies of data evaluation has yet to uncover many exciting opportunities for application in disaster management. The evaluation of landslide susceptibility usually deals with various combinations of geographical data sets including slope forms, catchment hydrology, stream hydrology, precipitation potential or rainstorm, soil saturation, soil strength, saturation potential and various derived forms of geological data. The difficulties associated with introducing a large data integrated system are first, having a systematic evaluation methodology which is practical, and second, having a set of scientific auxiliary decision methods to evaluate total significance. The Analytical Hierarchical Process (AHP) is a convenient way for quantitative analysis in decision making under a probabilistic environment and it is also an effective method for scientists to objectively provide subjective judgment. The AHP improves qualitative approaches on mutually exclusive dependencies or interdependencies of data and evaluates the significance in the Weighted Average Analysis (WAA) approach on landslide susceptibility. This qualitative approach will be further used to calibrate the large databases on landslide susceptibility evaluation with more and more interacting sets of data. The overall accuracy of the WAA model approach always depends on the sensitivity of the GIS databases and calibration through physically known datasets of landslide occurrences.

Ceylon Journal of Science, 2018

A light loving invasive shrub, Austroeupatorium inulifolium has been spreading many land use type... more A light loving invasive shrub, Austroeupatorium inulifolium has been spreading many land use types in the Knuckles Forest Reserve (KFR) in Sri Lanka, including man-made grasslands. In developing countries, there are limitations of using novel technologies to quantify and track the distribution of invasive species due to high costs and lack of facilities. This is a setback for their early detection and to introduce effective control measures. This pilot study attempted to map the distribution of A. inulifolium in man-made grasslands in KFR using high spatial multispectral images. Unsupervised, supervised and knowledge-based classifications were performed to quantify the spatial distribution of A. inulifolium in ERDAS Imagine. The results generated comparable results of the extent of area under A. inulifolium by using the unsupervised (108 ha), supervised (94 ha) and knowledge-based classifications (93 ha). They were 18, 15 and 15% from the total area selected for the study (622-646 ha), respectively. The results indicated the suitability of high spatial multispectral imageries in quantifying the spatial distribution of A. inulifolium. Further studies are recommended to investigate long-term changes in invasive plant population using multi temporal satellite data.

L. camara is currently invading many landuse types in Sri Lanka causing tremendous damage to the ... more L. camara is currently invading many landuse types in Sri Lanka causing tremendous damage to the natural and man-made ecosystems. Attention has been paid to control their spread mainly through chemical and physical means but with limited success. Understanding their ecological and physiological traits would be advantageous in order to introduce more efficient control measures in the future. The present study aims to investigate the competitive ability of L. camara when grown with a non-invasive, native Urena lobata using a pot experiment.

Book of Abstracts

Invasion of non-native plant species is an emerging problem worldwide including Sri Lanka. Invasi... more Invasion of non-native plant species is an emerging problem worldwide including Sri Lanka. Invasive alien species (IAS) cause problems to biodiversity and the economy of the country. Austroeupatorium inulifoilium has recently invaded the Knuckles Conservation Area (KCA) causing much damage to its environment. Initially, Austroeupatorium has confined to roadsides, disturbed areas and forest margins but now it has been vigorously spreading into grasslands and Pinus plantations. Information on their distribution and impacts are still scarce. This study is carried out to observe the distribution pattern of Austroeupatorium in grasslands at KCA.

Proceedings of the 2nd International Conference on Asian Studies (ICAS) 2014

The Cymbopogon nardus dominated grasslands in the Knuckles Conservation Area (KCA) have been rapi... more The Cymbopogon nardus dominated grasslands in the Knuckles Conservation Area (KCA) have been rapidly invaded by Austroeupatorium inulifolium over the past few years. A preliminary study indicated that Austroeupatorium has a facilitative effect on the establishment of forest tree seedlings on these highly degraded grasslands. This positive change perhaps due to enhanced micro-climate and edaphic parameters. We hypothesized that Austroeupatorium invasion can enhance soil nutrients through increased nutrient loading capacity via litterfall and decomposition processes. Two plant communities were selected as less-invaded (LIG) and highly-invaded grasslands (HIG) at KCA each with three replicate sites. From each plant community, surface soil samples were collected and air dried before analyzing for carbon (C), total nitrogen (N), total phosphorus (P) and pH. Litter decomposition experiment was conducted in situ using Austroeupatorium and Cymbopogon litter. Periodically collected litter samples were chemically analyzed. Surface and standing litter biomasses were sampled using three quadrates (0.625 m 2 and 0.25 m 2 respectively) from each site. Data were tested for normality and analyzed statistically using Minitab 14.1. Soil pH and soil N was significantly higher in HIG than that of LIG. However, soil C and P showed no significant differences between the two plant communities. Austrosupatorium litter quality (in terms of N and P) was higher than that of Cymbopogon. Austroeupatorium litter showed significantly lower C/N and C/P ratios compared to Cymbopogon. Austroeupatorium showed relatively higher decomposition rates compared to Cymbopogon. Nitrogen and phosphorus release patterns were during decomposition found to be slow in both Austroeupatorium and Cymbopogon irrespective of their habitats. Surface litter biomass was significantly higher in HIG (78 g/m 2 ) than in LIG (45.8 g/m 2 ). The standing litter biomass too showed significantly higher values in HIG compared to LIG. Austroeupatorium plants contributed significantly to the standing litter biomass in both LIG (75.9%) and HIG (75.9%). The higher litter contribution, quality and decomposition rates in Austroeupatorium may alter the soil nutrient pools over time. Such positive changes may help in the restoration of forests on these otherwise highly degraded grasslands in KCA.