Papers by Chandra Jayasena
Marine Pollution Bulletin, Jun 1, 2023
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Exposure and Health
The principal goal of the current study is to assess perchlorate contamination of groundwater and... more The principal goal of the current study is to assess perchlorate contamination of groundwater and related health risks from the fireworks manufacturing area (Sivakasi) in South India. Seventy-four groundwater samples were gathered and analysed for electrical conductivity (EC), pH, total dissolved solids (TDS), sodium (Na+), magnesium (Mg2+), calcium (Ca2+), potassium (K+), sulphate (SO42−), bicarbonate (HCO3−), chloride (Cl−), fluoride (F−), nitrate (NO3−), and perchlorate (ClO4−). Perchlorate ranged from 0.00 to 0.21 mg/l with an average of 0.08 mg/l. About 61% of the samples (n = 45) contained higher perchlorate concentrations than the recommended level (0.07 mg/L) of World Health Organization (WHO). Similarly, 360.18 km2 of area exceeds the permissible limit of perchlorate as per WHO. Correlation analysis indicates that groundwater contamination is mainly caused due to anthropogenic activities. Vertical distribution results indicate that 52% of the samples fall in the ‘high-risk’ category, 39% of the samples fall under the ‘very high-risk’ category and 9% of the samples fall under ‘safe’ category in the shallow aquifer of depth up to 15 m from the ground level. Total Hazard Index (THI) results reveal that about 70%, 60%, and 40% of the samples are more vulnerable (THI > 1) for infants, children, and adults. This study suggests that higher health risks inferred for infants must be cared with a suitable management plan to recover the quality of the water to evade major health problems in the future.
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LARHYSS Journal P-ISSN 1112-3680 / E-ISSN 2521-9782, Sep 30, 2021
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Proceedings of the International Association of Hydrological Sciences, 2018
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Ceylon Journal of Science, 2021
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Journal of Asian Earth Sciences, 2019
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Review of Palaeobotany and Palynology, 2018
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Slope failures causing landslides are common in many parts of Sri Lanka, particularly along the m... more Slope failures causing landslides are common in many parts of Sri Lanka, particularly along the major roads. Typically, conventional roller-compacted concrete or rubble-masonry structures have been used to mitigate such events but these methods have drawbacks, including the length of time taken to construct such structures. Therefore, alternative methods for stabilizing hazardous slopes need to be investigated. Among the alternative approaches are soil nailing, which involves the insertion of steel rods into an unstable slope to pin it in position, and soil bioengineering, which involves spraying a mixture of grass-seeds, other seeds and fertilizer onto a suitable matrix so that when the seeds germinate, the roots hold the underlying soil in place. Both methods can help to reduce construction times so that work can be completed before the onset of the annual rainy season. Soil-nailing and soil-bioengineering methods were introduced into Sri Lanka by Soil Tech Ltd., a private company.
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ABSTRACT
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A sequence of rhythmic varve like sediments within the valley of Weuda and isolated sand and grav... more A sequence of rhythmic varve like sediments within the valley of Weuda and isolated sand and gravel deposits in the northwestern plains of Sri Lanka, were reinvestigated. Inter-bedded peaty clay and sand intercalating with un-weathered feldspar, striated and faceted pentagonal quartzite pebbles, “U” shaped valley flanked with large boulders, isolated occurrences of poorly sorted white angular sands, ferruginized gravels and Permo-Triassic plant microfossils all favored a glacial origin for these sediments. However, Paleozoic glacial features appear to be either obliterated or erased due to post-glacial neotectonic movements, large scale pluvial processes, effects of denudation and intense tropical weathering. Study on provenance indicates that Paleozoic glacial deposits may have mixed with or covered by subsequent sediments.
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Water supply to arid areas by many ancient communities around the tropical and subtropical region... more Water supply to arid areas by many ancient communities around the tropical and subtropical regions was unique, where the conveyance mechanism had been developed based on morphological, geological and meteorological factors. However, to maintain the longevity and sustainability of these water supply systems, effective environmental management is imperative. Many medieval communities throughout these regions have practiced runoff harvesting to groundwater conservation in order to lead a sustainable life with the available rainfall. We postulated that integrated environmental criteria based on sound technical principles were fundamental for the establishment of the Tank Cascade (TC) and the Qanats irrigation systems. To carry out a comparative study and to investigate such mechanisms, we selected a dry zone catchment in the northwestern province of Sri Lanka and a Qanats based irrigation system in Iran. The TCS has evolved as a network of hydraulic structures, which have harnessed the ...
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Rural communities in the dry regions are continuously struggling with the meagre water resources ... more Rural communities in the dry regions are continuously struggling with the meagre water resources available to satisfy their daily household and agricultural needs. A pilot study conducted among 250 households from Aladeniya, Hedeniya, Weerakodiyana, Rakogama and Chilaw in the Deduru Oya basin during the period from 2002 to 2005 revealed that 80% of their daily needs are met with groundwater obtained from dug wells and tube wells. Approximately 82% of their average per capita daily domestic water consumption of 110 L was utilized for bathing while the remaining 18% was used for drinking, cooking, washing and toilets. The socio economic inputs show that the household income varies from Rs. 5,000/= - 15,000/= per month.And their willingness to pay for a reliable water supply system is little over 1.5% of their income, which is encouraging but very low to implement a modern water supply scheme. The average annual rainfall is 1600 mm, however geohydrologic environment is not conducive fo...
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Hydraulic properties obtained from pumping tests conducted in sedimentary and hard rock aquifers ... more Hydraulic properties obtained from pumping tests conducted in sedimentary and hard rock aquifers in Sri Lanka were examined. The test data were collected from Water Resources Board and National Water Supply and Drainage Board databases. The data were initially divided based on geology and treated separately. In the analysis, attention was paid only to 24 hr pumping tests and 72 hr recovery tests to minimize interferences. Theis's and Jacob's methods were used to evaluate the data before further analysis. Regional variations in the transmissivity (T) and storage co-efficient (S) of the aquifers were identified. The test data indicated that T and S vary from 1-1130 m 2
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Infrastructure development needs engineering judgments for which expensive geotechnical investiga... more Infrastructure development needs engineering judgments for which expensive geotechnical investigations are the prerequisite. Alternatively, few data points could model using geostatistics to obtain meaningful outcome. To test this, a project was formulated with 129 borehole data collected from the Kandy City Wastewater Project in Sri Lanka. Statistical analysis was initially conducted on declustered data plus supplement field data. After eliminating drift and removing extreme values, kriging were performed to obtain contour patterns. The depth to bedrock (DBR) contours show clear relation with lithology, fracture pattern and the topography. Quartzite and charnockite show shallow depths whereas marble and garnet sillimanite biotite gneiss show deep depths. However, deviations were observed in areas where anthropogenic inputs and exogenous processes are active. Depth to water table (DWT) and lithology does not show any relationship, however, DWT show compatible relationships with topo...
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Applied Geochemistry, 2015
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Since 3rd century BC tank cascade systems in the lowlands within the dry and interme- diate zones... more Since 3rd century BC tank cascade systems in the lowlands within the dry and interme- diate zones of Sri Lanka have evolved in order to efficiently manage the surface water re- sources. The spatial distribution of tanks as exemplified by the topographic maps seems to follow a regular pattern. This study was conducted with data collected from 4633 tanks, to understand the distribution pattern of tanks in cascades in the Deduru Oya river basin. This river basin recorded the highest tank density (one tank in terms of numbers per 1.2 km2) in Sri Lanka. We devised a tank sequence number and assigned to each tank along the axes of the watersheds. Based on rainfall regime of 100mm intervals over individual cas- cades, the sequence number variations were plotted considering rainfall regime and cas- cade characteristics. The results indicate that the number of tanks against the tank se- quence number is following a log linear relationship in which the gradient varies from - 0.210 (1200-1300 ...
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Papers by Chandra Jayasena
H. A. H. Jayasena
Department of Geology, University of Peradeniya, Peradeniya 20400, Sri Lanka
(corresponding author phone: +94-727-435-161; fax: +94-812-388-018; e-mail: cjayasena@ pdn.ac.lk)
Abstract
Among the ancient irrigation practices, the Sri Lankan dry zone water management systems sustained for over 2000 years have been well documented. With the influx of communities settling around the historical urban centers, efficient water management was necessary. The invention of the Tank Cascaded system (TCS) and a network of canal systems have emerged to supply water to these centers, which lasted even at present. This paper aims at unraveling some unique functions of the Yoda Ela (YE) canal located in the northern dry zone connecting Kala Wewa (reservoir) with Tissa Wewa. After examining the aerial photographs, Google Earth Pro, and Digital Elevation Models (DEM) followed by field investigations to assess the respective environmental changes, it was evident that the water supply from a transboundary canal took place with the utmost care and in a sustainable manner. Minimal hydrochemical variations and sediment migration coupled with well-maintained irrigation and domestic water supply sustain the community living around this 87 km long canal. The Yoda Ela is one of the excellent representations exemplifying the urban-rural linkages from the total environment and global water history perspectives.
Keywords—Total environment, Dry zone irrigation, Sustainability, Yoda Ela, Urban-rural
Keywords: Construction dewatering, hydraulic conductivity (K), Transmissivity (T), Storage Coefficient (S), regulatory framework, glacial, hard rock, Orbit, Sri Lanka, Canada
Acknowledgements: The first author acknowledges the University of Peradeniya for giving him the opportunity to spend his sabbatical leave at the Orbit Engineering, Brampton, Canada.
Keywords: NW Sri Lanka, Water consumption, dry Zone, hydrogeology, SDG
Ranathunga, B.P.D.W.1, Chandrasena, M.G.P.N.2, Jayasena, H.A.H.3 and Chandrajith, R.3
1.National Building Research Organization, 99/1, Jawatta Road, Colombo 00500, Sri Lanka.
2.Post Graduate Institute of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka.
3.Department of Geology, Faculty of Science, University of Peradeniya, Peradeniya 20400, Sri Lanka.
ABSTRACT
The ancient “Yoda Ela Canal” (YEC), which drives water from “Kala Wewa” to “Thissa Wewa” reservoirs in the dry zone of Sri Lanka, has been abandoned with the recent reconstructions of new “Jaya Ganga Channel” (JGC). A questionnaire-based survey (N = 50) supported by 19 groundwater and 12 surface water samples collected from 11 locations along YEC was used to assess the people's perception, geochemical characteristics, longitudinal variations and suitability of water for drinking and irrigation purposes. Electrical Conductivity (EC), Residual Sodium Carbonate (RSC), Sodium Adsorption Ratio (SAR), Kelley’s Ratio (KR) and Magnesium Hazard (Mg Haz.) were evaluated to map the longitudinal variations. Suitability of YEC water for irrigation purposes was classified based on the US salinity diagram. The EC, RSC, KR and Mg Haz show cumulative variations along with the longitudinal profile from good to doubtful water qualities. Statistical analyses including cluster analysis (CA), correlation matrix and principal component analysis (PCA) were performed on data and the results suggest significant influences of geogenic processes on both surface water and groundwater systems. For both systems, the Piper diagram indicates Ca-Mg-HCO3- types while the Gibbs diagram depicts rock dominant processes. The questionnaire survey indicated that the impacts of agrochemical pollution along with the YEC refrain the community to drink water from the open source. The overall analyses specified that both surface and groundwater systems along the YEC were progressively influenced by the rock-water interaction and anthropogenic inputs. Though the majority believe JGC increases the water supply, the overall system has been deteriorating in terms of sustainability, longevity and agrochemical usage. The study clearly indicates that the time-tested sustainable water allocation from ancient YEC is gradually obliterated by modernization and anthropogenic impacts.
Yoda Ela, Jaya Ganga, water chemistry, sociotechnology, Sri Lanka
Highlights (50 words) *
Politically motivated reconstruction of modern Jaya Ganga Channel (JGC) over the ancient Yoda Ela canal (YEC) has obliterated the sustainable water allocation and livelihood of farmers. Both surface and groundwater quality along the YEC are influenced by the rock-water interaction due to deepening of YEC and heavy agrochemical usage.
Summary (150 words) *
Groundwater (19) and surface water (12) samples from 11 locations along YEC were analysed to assess geochemistry and drinking and irrigation suitability. Electrical Conductivity, Residual Sodium Carbonate, Sodium Adsorption Ratio, Kelley’s Ratio and magnesium hazard variations show water quality varying from good to doubtful along the YEC. Cluster analysis, correlation matrix and principal component analysis were performed, and the results suggested significant influences of geogenic processes on both surface and groundwater systems. For both systems, the Piper diagram indicates Ca-Mg-HCO3- types while the Gibbs diagram depicts rock dominant processes. A questionnaire survey (N=50) indicated that agrochemical pollution was increased towards the downstream refraining community to drink water from the open-source. The majority believe JGC increases the water supply, however, it has been deteriorating in terms of sustainability, longevity and agrochemical usage. The study clearly indicates that the time-tested sustainable water allocation from ancient YEC is obliterated by modernization and anthropogenic impacts.
Overall Introduction and objectives (100 words) *
The ancient YEC carries water from Kala Wewa to Thissa Wewa reservoirs in the dry zone of Sri Lanka. The YEC sustained over 1500 years providing quality irrigation water and sustainable livelihood. However, the construction of JGC severely affects sustainability. The study aims at understanding the YEC flow regime, in terms of its geochemical variations of surface and groundwater, and environmental changes and damages. In addition, the suitability of water for drinking and agriculture are duly assigned for the study so that the pros and cons of the modernization process would be tested.
Methodology Approach with the description of the innovative approaches or analytical tool (200 words) *
The literature on YEC and JGC were compiled for a preliminary assessment. The data on geology, structure, morphology and dry zone tank cascade systems was also collected through primary sources before fieldwork starts in the selected areas. A questionnaire-based survey (n = 50) was used to assess people's perception. Nineteen groundwater from surrounding wells and twelve surface water samples were collected from 11 locations along YEC to asses the geochemical variations and suitability of water for drinking and irrigation purposes. The water samples were collected into polyethylene bottles (500 ml bottles for anions and 100 ml bottles for cations) that sank in 10% HNO3 overnight and washed with distilled water. Each 100 ml sample was filtered and acidified by conc. HNO3 acid to prevent the cations loss or change due to adsorption or exchange with a wall of the bottle. Water and air temperatures, pH, electrical conductivity (EC), and Total Dissolved Solids (TDS) of water were measured using portable meters. Major cation and anion concentrations were measured in the lab. For both surface and groundwater systems, the Piper and Gibbs diagrams were prepared. The GIS and statistical software were used to construct maps, longitudinal profiles, cluster analysis, correlation matrix and principal component analysis.
Why is the current approach/innovation relevant? What are the benefits and for whom? (100 words) *
It has been noted that politically motivated systems usually geared for short term goals ended up with miscalculations of the expected output. A classic example is the conversion of ancient YEC, which supported the sustainable livelihood, to a modern JGC obliterating expected overall benefits. The present study aims at unravelling the cumulative effects when the anthropogenic elements work on building unsustainability. Anthropogenic inputs and agrochemicals causing a severe backlash to the time tested sustainable total environment associated with the YEC. We believe the paper highlights the repercussions of ad hoc decision making without major concern on environmental goals.
Analysis and results with examples of actual application of the scientific innovation or activity or analytical tool (200 words) *
The EC, Residual Sodium Carbonate (RSC), Sodium Adsorption Ratio (SAR), Kelley’s Ratio (KR) and magnesium hazard (Mg Haz.) show variations along with the longitudinal profile of YEC from good to doubtful water qualities. Irrigation suitability based on the US salinity diagram indicates medium to high salinity hazard in most locations. The physical parameters and chemical concentrations of anions and cations are used as variables for the cluster analysis and the results show surface water quality varies from good to bad towards downstream. The dendrograms are performed separately for surface and groundwater system. Principal component analysis (PCA) results suggested significant influences of geogenic processes on both surface and groundwater systems. The Piper diagram for both systems indicates Ca-Mg-HCO3- types while the Gibbs diagram depicts rock dominant processes. The questionnaire survey indicated that agrochemical pollution was increased towards the downstream of the YEC refraining community to drink water from the open-source. The overall analyses indicated that both surface and groundwater systems along the YEC were influenced by the rock-water interaction and anthropogenic inputs.
Conclusions and recommendations (100 words) *
The overall analyses indicated that both surface and groundwater systems along the YEC were influenced by the rock-water interaction and anthropogenic inputs after the construction of new JGC. Though the majority believe JGC increases the water supply, the overall system has been deteriorating in terms of sustainability, longevity and agrochemical usage. The study clearly indicates that the time-tested sustainable water allocation from ancient YEC is obliterated by modernization and anthropogenic impacts. It is recommended that political driven motivation on the reconstruction of existing ancient irrigation networks need prior evaluations considering total environmental issues before implementation.
for efficiency. A structured survey was conducted for 180 families randomly selected from Hedeniya and Aladeniya in the wet zone as well as Rakogama and Weerakodiyana in the intermediate
zone. The results show that the average daily usage for drinking, cooking and sanitation is 115 l/p/d (liters per person per day) out of which more than 70% is used for bathing. Currently 65% use dug wells and another 16% use Tube wells while pipe born water supply is available for only 6% of the families. Contributors believe domestic water supply programs could be organized through dug wells and tube wells; however reservoirs and streams could be added in the lowland planes too. The satisfaction
over water supply and maintenance by different agencies such as government, provincial councils, private sector, NGO, foreign agencies, regional councils and other agencies were also examined. The
contributors prefer water supply and maintenance responsibilities be handled by the central government. However, more than 60% of contributors from Hedeniya were extremely satisfied with NGO
and Foreign Agency involvement, since a FINNIDA supported water supply and sanitation project was successfully completed in Hedeniya. Major complaints of these projects were the inadequate maintenance
and inefficiency of officials. A WTP survey was conducted for future water supply projects anticipated in these villages where the monthly income varies from Rs. 5000 in Hedeniya to more than
Rs.15000 in Aladeniya. This survey indicates community agreement for allocation of at least 1.5% from the average monthly income. However, contributors from severe water shortage areas such as Rakogama and Hedeniya prefer allocation of more than 3.5% from the average monthly income even though their average expenditure was below the average poverty set at Rs. 1423 /p/month (per person per month). The study concluded that strong government subsidies are needed in water supply projects. People expect strong management initiatives in order to provide efficient water supply programs in Sri Lanka
Structural and Hydrogeological framework: The basement comprises with high grade metamorphic rocks such as marble, garnet biotite gneiss, garnet sillimanite biotite gneiss ± graphite (khondalite), quartzo feldspathic gneiss, charnockitic gneiss and quartzite. Quartzite is present as minor bands within khondalite, however marble is well exposed as continuous bands. General strike of the rocks are in north south direction with few degrees towards NNW or NNE. However, dips vary from 10° to vertical showing wide variations. Major lineaments are running in E-W and N-S directions. Rose diagrams clearly show EW
and N-S system with minor NE-SW and NW-SE joint systems. Maximum stress is nearly in the north-south direction, which resulted in E-W joint set and lineaments. The area is covered by a thin mantle of weathered products either derived from the parent rock (residual) or transported material. Colluvium and residual weathered products consist of a wide range of poorly sorted material with varying sizes from boulders to clay. Alluvial materials tend to be sorted along the flood plain whereas the level of sorting depends on the provenance. Reddish brown lateritic soil is developed on the crystalline limestone and show varying
thicknesses up to 50 m. Brown sandy clay on khondalite however, contains a hardpan developed by the subsurface soil water movement. Groundwater table exposed at springs in the central valley and extended to 39 meters below ground level in the elevated rocky hinterlands. Springs: Springs are located along with marble and discharge their waters through karst formations and along solution paths of joints, fractures and coarse grains. Rainfall is the main recharging
factor for these springs which shows a bimodal distribution with a clear cyclicity. A considerable seasonal yield variations as observed at certain springs clearly reflect the rainfall distribution. The yield of rainy season varies from 20-1500 l/min while in the dry season it varies from 10-876 l/min with a general trend of increasing yields towards north. Based on borehole records and field observations, groundwater level and the bed rock surface of the study area varies from the surface up to 39 and 50m depths respectively. High yields can be envisaged in areas where springs emitting out from marble, especially when shallow water levels, significant fracture intensities and solution cavities are present. Three marble bands are prominent in the study area. There is no any systematic distribution of springs among them, however, clusters are concentrated in the middle band and in association with folding of rock layers. Four different genetic types of springs can be identified viz: 1. associated with well-developed karstic formations, 2 along with primary joints and fractures, 3. through secondary porosity and permeability, 4. locations where coarse grain marble present. Among them Matale springs are dominated by fractures and joints. Many are formed
in association with E-W and NE-SW trending fractures. However, meso scale folds are responsible for few springs. Springs are generally confined to the areas where slope angle is up to 10° within the regional catchment. Many springs are located within 50 meters from the stream indicating significant groundwater supply from the effluent system, so that the recharge is most likely originated from the rainfall in the elevated highlands. Based on cumulative discharge of 7560
l/min and assuming per capita daily requirement of 110 l, over 100,000 persons can be served by the spring water. Conclusion: This study concluded that in the heart of Sri Lankan highlands, spring water could play a major role in domestic circles. It could also effectively support small scale commercial and industrial establishments and irrigation sectors. The springs emitting through karstic formations have high yields compared with those emitting from fractures and solution cavities. Since the springs are mainly recharged by ample rainfall, they provide good yields throughout the year. The forgoing discussion reveals that springs in marble formation indicate a good potential for developing as a community water supply scheme where it could serve a one fourth of the community living in the area.
Key words:Palynology, Fungi, palaeoenvironment, Scolecodont, Chitinozoa. Thecamoebians
Prof. H.A.H. Jayasena is a Professor in Geology at the University of Peradeniya, Sri Lanka. He earned his bachelors from Peradeniya and Post degrees from CSU, Fort Collins, and ORST, Corvallis, USA. He is a Chartered Geologist (Sri Lanka), a Provisional Member of APGO (Canada) and a Registered Practitioner in Hydrogeology of the Central Environmental Authority (Sri Lanka). He served as a consultant to dam and tunnel construction, slope stability & landslide remediation, EIA & ESA, and mining projects, in addition, to play a major role in high-end donor-driven (WB, ADB, JBIC, and UNDP) water projects. He has secured over Rs. 15 million and US$ 70,000 worth research and educational funds. He has published 53 peer-reviewed articles, 22 research reports and 56 abstracts in reputed local and international journals. He served as Chairmen of Geotechnical Engineering Companies, President of the Geological Society, and Member of the UN Geothermal Project in Sri Lanka.