-1DWQ6FL)RXQGDWLRQ6UL/DQND DOI: http://dx.doi.org/10.4038/jnsfsr.v47i3.9281
RESEARCH ARTICLE
Distributed modelling of water resources and pollute transport in Malwathu Oya Basin, Sri Lanka
A.C. Dahanayake * and R.L.H.L. Rajapakse 'HSDUWPHQWRI&LYLO(QJLQHHULQJ)DFXOW\RI(QJLQHHULQJ8QLYHUVLW\RI0RUDWXZD.DWXEHGGD0RUDWXZD
Submitted: 04 April 2018; Revised: 11 April 2019; Accepted: 03 May 2019
Abstract: The Nachchaduwa sub-catchment (598.74 km 2) of the Malwathu Oya basin is seasonally stressed in the dry INTRODUCTION SHULRGVDQGLWVGRZQVWUHDPSDUWVXQGHUJRLQWHUPLWWHQWÀRRGV during monsoon seasons while the fate and behaviour of excess Water, being a vital natural resource to sustain all life QLWURJHQ 1 DQGSKRVSKRUXV 3 DGGHGWRWKHZDWHUZD\VGXH forms on earth, has now become a limited resource due to to agricultural fertilisers used in the upstream areas remain the adverse impacts of various natural and anthropogenic unresolved. This study incorporated the Water and Energy causes. Due to the increasing population and rapid 7UDQVIHU3URFHVVHV :(3 PRGHOWRDVVHVVWKHSUHVHQWVWDWXV urbanisation, the demand for water has been increasing of the catchment concerning water resources and pollutant drastically. Further, the quality of the available fresh transport. Results showed that the catchment response to the water resources has been deteriorating mainly due to UDLQIDOO LV KLJKO\ UHJXODWHG GXH WR UHVHUYRLU VWRUDJH H൵HFW pollution created by the anthropogenic activities in many XQJDXJHGEDVLQZLWKUHJXODWHGÀRZV 7KHDPRXQWVRI1DQG3 rivers in developing countries, which has become a threat in fertilisers applied in this catchment exceeded the actual plant to the ecosystem and to human health. requirement. In both wet [Maha cultivation season (October to March)] and dry [Yala cultivation season (April to September)] VHDVRQVWKHGL൵HUHQFHVEHWZHHQWKHXSVWUHDPDQGGRZQVWUHDP Malwathu Oya basin is the second largest catchment 2 YDOXHV RI PHDVXUHG ZDWHU TXDOLW\ SDUDPHWHUV 1 DQG 3 among the river basins in Sri Lanka (3284 km ), and one components - total, dissolved and particulate) in waterways of the most widely used sources of water for irrigation, ZHUHQRWVWDWLVWLFDOO\VLJQL¿FDQW2QDYHUDJHWKHZHWVHDVRQ water supply and other diversions in the North Central had about 5~7 timesି the dry season value of the total suspended 3URYLQFH )LJXUH ,W KDV QRZ EHFRPH D VHDVRQDOO\ ଷ solids (TSS) in the streams, and in both seasons, the modelled stressed river basin due to over exploitation and water TSS, and were within the ranges of the previously pollution. The basin experiences water scarcity during the publishedି results. Thisଷି study will be continued in the future to ଷ ସ dry periods and the downstream areas of the catchment analyse possible hydrological and material transport related DUHÀRRGHGGXULQJWKHZHWSHULRGVZKLOVWVHYHUHÀRRGLQJ scenarios to identify best water resources management practices was observed in 2011, 2014 and 2016 ( 'HSDUWPHQW RI and to pragmaticallyଷି cope with the excess fertiliser usage, an ସ issue commonly found in most of the similar catchments. ,UULJDWLRQXQSXEOLVKHGGDWD .
Keywords: Nachchaduwa, nitrogen, nutrient concentrations, The basin is augmented by the adjacent Kala SKRVSKRUXV766:(3PRGHO Oya basin from Kala Wewa reservoir via Yoda Ela to
* Corresponding author ([email protected]; https://orcid.org/0000-0002-4400-6979)
This article is published under the Creative Commons CC-BY-ND License (http://creativecommons.org/licenses/by-nd/4.0/). This license permits use, distribution and reproduction, commercial and non-commercial, provided that the original work is properly cited and is not changed in anyway. $&'DKDQD\DNH 5/+/5DMDSDNVH )LJXUHV ORFDWLRQVGXULQJFXOWLYDWLRQVHDVRQV 3HUHUD et al ., 2014). The stream has been (mis) used as a site for waste disposal in the urban area and water becomes polluted easily (De Alwis, 2006). ି ଷ 6LJQL¿FDQWO\KLJKHUFRQFHQWUDWLRQVRI , and – Cl LQ VWUHDPV GXULQJ WKH ¿UVW LQWHUPRQVRRQି ଷି VHDVRQ (March-April) in the paddy growing areas ଷ have ସ been observed, along with the highest mean dissolved oxygen (DO) and turbidity values observed in the northeast ଷି monsoon season (December-February) inସ Malwathu Oya. The chemical fertiliser application with the paddy FXOWLYDWLRQLVFRQWULEXWLQJWRWKHVWDWLVWLFDOO\VLJQL¿FDQW seasonal variations observed in the water quality SDUDPHWHUV 3HUHUD et al ., 2014). In addition the outlet of the main stream from the Anuradhapura city and the ି FDQDOÀRZLQJDFURVVWKHFLW\KDYHVKRZQKLJKHUYDOXHV ଷ for total dissolved solids, pH, electrical conductivity, DO level, , and FRQ¿UPLQJ WKH LPSDFW RI urban land useି on waterଷି pollution in Malwathu Oya (Madushanka ଷet al ., 2015). ସ In addition, the fate and EHKDYLRXURIH[FHVV1DQG3DGGHGWRWKHZDWHUZD\VDV fertilisers applied in paddy lands and other crop areas in ଷି the upstream ସ catchment areas remain unresolved, and suspected to be a cause of the high prevalence of chronic kidney disease of unknown aetiology (CKDu) in the area (Munasinghe et al ., 2015). )LJXUH 1DFKFKDGXZDFDWFKPHQWDQGWKHGHOLQHDWLRQRIVXEFDWFKPHQWV Figure 1: Nachchaduwa catchment and the delineation of Therefore, water resources management alternatives sub-catchments (to overcome issues occurring due to water scarcity, climate change impact, etc.) and measures to address feed Nachchaduwa, Tissa wewa and Basawakkulama issues related to degrading water quality (caused due to reservoirs. The basin is distinct as it possesses a large excessive use of fertilisers and agro-chemicals etc.) in number of tanks, from small size village tanks to the basin should be studied, while the fate of pollutants comparatively fair-sized tanks, from which the rainfall including their conveyance and spatial and temporal UXQR൵ SURFHVV LV ODUJHO\ LQÀXHQFHG 8S WR D FHUWDLQ accumulation patterns should also be investigated by WKUHVKROG WKH ULYHU ÀRZ LV PRUH RU OHVV UHJXODWHG DQG studying the dispersal and accumulation behaviour of ÀRRG SHDNV DUH UHGXFHG 'HSDUWPHQW RI ,UULJDWLRQ these elements after they have been added to the crop XQSXEOLVKHGGDWD ). However, the water holding capacity ¿HOGVDQGZDWHUZD\V RIPRVWRIWKHWDQNVKDVEHHQUHGXFHGVLJQL¿FDQWO\GXH to aquatic weeds, eutrophication and heavy siltation. 3K\VLFVEDVHG GLVWULEXWHG K\GURORJLFDO PRGHOV Hence, most of the tanks are facilitating only for Maha can take account of temporal and spatial variations season and lack of irrigation water has become a problem of all variables and parameters involved in the basic in the Yala season (Gunarathna & Kumari, 2014). PDWKHPDWLFDO HTXDWLRQV RI WKH ZDWHU ÀRZV IRU D watershed. In addition, the used parameters are physically Anthropogenic activities cause stresses on Malwathu measurable. Therefore, they give a detailed and 2\DE\LPSDLULQJWKHTXDOLW\RILWVZDWHU 3HUHUD et al ., potentially more correct descriptionϮϮ of the hydrological 2014). With respect to irrigation-related water quality of processes in the watershed than empirical and conceptual the reservoirs, Nachchaduwa has exceeded the threshold hydrological models. Today, there exist several popular value of electrical conductivity (0.750 mScm -1 ) and models of this type, like SHE, IHDM, SWAT, MIKE salinity (0.500 gL -1 ) (Silva, 2004). Water of the nearby SHE (Jia et al D DQG :(3 :DWHU DQG (QHUJ\ SDGG\ ODQGV LV GLYHUWHG WR WKH ULYHU IURP GL൵HUHQW WUDQVIHU3URFHVVHV PRGHO -LD et al ., 2001b).
September 2019 Journal of the National Science Foundation of Sri Lanka 47(3) :DWHUUHVRXUFHVDQGSROOXWHWUDQVSRUWPRGHOOLQJ
7KH :(3 PRGHO KDV EHHQ GHYHORSHG E\ DGGLQJ PRUH The entire catchment has been delineated into three detailed energy balance analysis in hydrological modelling sub-catchments according to the terrain and stream path -LD 7DPDL ,WV PDLQ GL൵HUHQFHV IURP RWKHU distribution (Figure 1). physics-based models involve detailed consideration of energy transfer processes, use of sub- grid heterogeneity Collection and pre-processing of data of land use, application of generalised Green-Ampt model to save computation time and its potential use for The model input data required for the hydrological various scenario analyses. It has been further improved component and the material transport component were by coupling a soil erosion-transport model to introduce FROOHFWHG DQG SURFHVVHG 6WUHDPÀRZ UHODWHG GDWD DQG a particle-bound pollutant component (Rajapakse Nachchaduwa reservoir operation data (sluice release, et al ., 2010), and by adding simulation of multi-layered spill release, water issues, irrigation issues, etc.) were DTXLIHUVGLUHFWFRPSXWDWLRQRIJURXQGZDWHURXWÀRZWR collected from the Department of Irrigation. Land use ULYHUVDQGVLPXODWLRQRILQ¿OWUDWLRQWUHQFKHV,WKDVEHHQ details and soil types of the catchment were extracted successfully applied to river basins in Japan, Korea and from the spatial maps prepared by the Survey Department China (Jia et al ., 2001a; 2001b; 2007; Rajapakse et al ., in year 2001. Geological and soil layer details were 2010; Cunwen et al ., 2011). Detailed descriptions of obtained from the borehole data of the construction model development, hydrologic and material transport projects undertaken in the close proximity. modelling procedures and input/output data, are given in the literature [Jia et al . (2001a; 2001b; 2005) and Meteorological data including rainfall, temperature, Rajapakse et al. (2010)]. wind velocity, relative humidity and sunshine hours were collected from the Meteorological Department 7KHUHIRUH WKH SUHVHQW VWXG\ LQFRUSRUDWHG WKH :(3 and checked using the hydrological and statistical data model to the Nachchaduwa sub-catchment to assess the checking procedures. Daily rainfall data for the stations, current status of the basin concerning the water resources Anuradhapura, Kahatagasdigiliya, Kekirawa, Maha management and pollute transport. ,OOXSSDOODPD DQG 3HOZHKHUD ZHUH FROOHFWHG DQG WKH Thiessen average daily rainfall values were calculated. METHODOLOGY 7KH:(3PRGHOKDVWKHFDSDFLW\WRVLPXODWHKRXUO\ Study area data. Since hourly data were not available, it was checked whether an improvement could be made by Nachchaduwa catchment was selected as the study area using hourly data generated from daily data, following since it is the uppermost sub-catchment in the Malwathu the Disaggregated Rainfall Method (Bennett et al ., 2\DEDVLQWKHUHIRUHQRH൵HFWIURPXSVWUHDPFDWFKPHQWV 2015). Excel Visual Basic for Applications (VBA) was have to be considered. Further, because of the location used for data pre-processing and to prepare the input RI D PDMRU UHVHUYRLU WKH UHVHUYRLU H൵HFW FRXOG DOVR EH ¿OHVQHFHVVDU\IRUWKHPRGHOUXQV)RUFDOLEUDWLRQGDWD modelled. from year 2008 to 2011 and for validation, data from year 2012 to 2015, were used. Nachchaduwa reservoir is managed by the Department of Irrigation and it is fed by the Malwathu 'HYHORSPHQWRIVWUHDPÀRZGDWDVHULHV Oya and the feeder canal from Kala wewa. It has an irrigable area of 2833 ha and a catchment area of 7KH VWUHDPÀRZ DQG UHVHUYRLU RSHUDWLRQ GDWD ZHUH 598.74 km2. checked against the rainfall values to identify the catchment response and impact of reservoir storage. The Nachchaduwa catchment consists of several land PRQWKO\DQGDQQXDOUXQR൵FRH൶FLHQWVZHUHFDOFXODWHG use types, which include chena, forests, home gardens/ DQGWKHUHVSRQVHRIWKHFDWFKPHQW WRWDORXWÀRZIURPWKH gardens, other cultivations, paddy, rock, scrub land, reservoir) with precipitation was checked. It was noted as well as water bodies. According to the digital maps WKDWGXULQJFHUWDLQ\HDUVWKHUDLQIDOODQGWRWDORXWÀRZ prepared by the Survey Department of Sri Lanka in year from the reservoir do not show a good correlation due 2001, the soil types of the catchment are mainly composed to lack of reliable reservoir operation related data. The RIDOOXYLDOVRLOVRIYDULDEOHWH[WXUHDQGGUDLQDJH LQÀDW catchment response to the rainfall indicated that the terrain) in the vicinity of the stream paths and reddish- measured spill and total release data are highly regulated brown earths and low humic gley soils everywhere else. GXH WR UHVHUYRLU VWRUDJH H൵HFW XQJDXJHG EDVLQ DQG
Journal of the National Science Foundation of Sri Lanka 47(3) September 2019 $&'DKDQD\DNH 5/+/5DMDSDNVH ି ି ଷ ଷ UHJXODWHG ÀRZV 'XH WR WKHVH UHDVRQV D SUHYLRXVO\ each, were collected from all the locations. The samples ି calibrated HEC-HMS [Hydrologic Engineering Centre’s ZHUHWHVWHGIRU1DQG3XVLQJWKHSHUVXOIDWHPHWKRGIRU ଷ Hydrologic Modelling System, developed by the United simultaneous determination of total nitrogen and total ି ଶ States Army Corps of Engineers (USACE)] model SKRVSKRUXV $3+$ 7KHVDPSOHVZHUHFKHFNHGି ଶ that was developed for this catchment was applied in for the concentrations of anions (such as , and the present study by incorporating the most suitable ) in ppm by usingଷି the 930 Compact ICି Flexି Ion ସ ଷ ଶ parameter values taken from previously published studies Chromatographyଷି system (Metrohm AG, Switzerland). ସ (loss method - soil moisture accounting, transform For checking the -N, the UDK 149 Automaticି ଷି ଷ ି ା PHWKRG &ODUN XQLW K\GURJUDSK PHWKRG EDVHÀRZ .MHOGDKO 'LVWLOODWLRQ 8QLWସ 9(/3 6FLHQWL¿FD 6UOସ ,WDO\ ଷ method - constant monthly method) (Hettiarachchi, was used. ି .DPUDQ 5DMDSDNVH 7KHRXWÀRZYDOXHV ଶ from the total basin were obtained for a 1 h time interval ି 7KH SUHYLRXVଷ WHVW UHVXOWV ZHUH FRQ¿UPHG ି E\ ଶ IURPWKH+(&+06PRGHODQGXVHGDVWKHVWUHDPÀRZ FRQGXFWLQJି FRORXULPHWULF WHVWLQJ XVLQJ WKHଷି 3DOLQWHVW ଶ ସ GDWDVHULHVIRUFRPSDULVRQZLWKWKH:(3PRGHO 3KRWRPHWHU 3DOLQWHVW /WG (QJODQG )RU GHWHUPLQLQJ , and WKH3DOLQWHVW3KRVSKDWH3DOLQWHVWଷି ସ Water balance and yield analysis 1LWURFRODQGWKH3DOLQWHVW1LWUDWHVWPHWKRGVZHUHXVHGଷି ି ି ସ ଶ ଷ The colourimeter was used for determining by A situation analysis was carried out by conducting Nessler’s method. ା ସ a yield analysis to verify the current water scarce ଷି ସ situation in the Nachchaduwa sub-catchment. Irrigation Fertiliser input dataି requirement was calculated considering the current ଶ practice in the scheme; low land paddy (135 days) for the Fertiliser issuance data for urea [CO(NH 2)2], triple super ଷି Maha season and low land paddy (105 days) and other SKRVSKDWH 763 ସ >&D + 232 4)2.H 2O] and muriate of ¿HOGFURSV 2)& IRUWKH September 2019 Journal of the National Science Foundation of Sri Lanka 47(3) :DWHUUHVRXUFHVDQGSROOXWHWUDQVSRUWPRGHOOLQJ Table 1: Required amounts of fertilisers for crops Crop type Growth stage Required amount Yala Maha Reference/remarks Day of transplanting 40 kg/ha phosphorus April October (basal application) Active tillering 20 kg/ha nitrogen November, 8QLWHG6WDWHV3HDFH 3DGG\ May, June ¿UVWWRSGUHVVLQJ 20 kg/ha potassium December Corps (1980) 3DQLFOHLQLWLDWLRQ 20 kg/ ha nitrogen July, August, January, February, (second top dressing) 20 kg/ha potassium September March Basal dressing 16.1 kg/ha nitrogen April October (before sowing) 45 kg/ha phosphorus Mung beans (Field Top dressing November, Crops Research and Other crops 13.8 kg/ha nitrogen May, June DWÀRZHULQJ December Development Institute, July, August, January, February, n.d.) No fertiliser required September March Basal dressing 3.22 kg/ha nitrogen April October $VVXPSWLRQ RQH¿IWK (before sowing) 9 kg/ha phosphorus of the required amount Top dressing November, for other crops (Field Homesteads 2.76 kg/ha nitrogen May, June DWÀRZHULQJ December Crops Research and July, August, January, February, Development Institute, No fertiliser required September March n.d.) obtained by the Survey Department had a resolution of assumed that the total amount of nutrients a plant would P,WZDVUHFODVVL¿HGXVLQJ$UF*,6WRREWDLQD absorb (kg) is equal to the required amount to the plant. m × 300 m resolution grid for the catchment. The input The amount of N was presumed as the summation of the ¿OHVFRQWDLQLQJWKHHOHYDWLRQVORSHÀRZGLUHFWLRQDQG amount added by fertiliser and the amount produced in ÀRZDFFXPXODWLRQRIHDFKJULGFHOOZHUHGHYHORSHGE\ IDUPODQGV IURP 1 ¿[DWLRQ >E\ OLJKWHQLQJ 0L\DPRWR using ArcGIS and Excel VBA macros. The stream was et al ., 2008), combustion (Deacon, n.d.), and plant N divided into 13 channel sections. For this study, 9 soil ¿[DWLRQ &DVK et al ., 1981; Walley et al ., 1996)]. De- layers; interception layer, depression layer, three upper QLWUL¿FDWLRQ ZDV DQDO\VHG E\ WKH PRGHO LWVHOI )XUWKHU soil layers (thickness 0.2 m, 0.4 m, 1.4 m), transition details of the modelling approach of the non-point and point sources of pollution are given in Rajapakse et al . OD\HU P XQFRQ¿QHGDTXLIHU P DTXLWDUG (2010). P FRQ¿QHG DTXLIHU P DTXLWDUG P DQG FRQ¿QHGDTXLIHU P ZHUHFRQVLGHUHGEDVHGRQWKH $SDUWIURPWKHVHLQSXW¿OHVUHODWHGWRWKHFRQWUROOLQJ actual formation of strata in the soil. The thickness of parameters, sub-catchment delineation, land use, each layer and initial moisture content of each surface meteorological data, soil parameters, river channel soil layer (3 layers) in each grid, were given as related element details, aquifer details, initial groundwater LQSXW ¿OHV 7KH *UDPD 1LODGDUL 'LYLVLRQ *1' ZLVH levels, etc. have also been prepared for the model runs. population and water supply data for the year 2012 were found from the statistical reports published (Department Parameter sensitivity analysis of Census and Statistics-Sri Lanka, 2012). The population density and the well density related to each cell were 7KH VHQVLWLYLW\ RI WKH :(3 PRGHO UHVXOWV WR DOO WKH FRPSXWHGWRSUHSDUHUHOHYDQWLQSXW¿OHV SDUDPHWHUV JRYHUQLQJ WKH ZDWHU TXDOLW\ ZDV LGHQWL¿HG by varying the parameter values within a pre-determined )XUWKHU LQSXW ¿OHV IRU WKH PDWHULDO WUDQVSRUW UDQJH DQGFRPSDULQJWKH:(3PRGHOUHVXOWV component were prepared using the previously calculated with the previously published water quality data in the IHUWLOLVHUGDWDIRUDOOFURSVFRQVLGHULQJ1DQG3,WZDV same basin. Journal of the National Science Foundation of Sri Lanka 47(3) September 2019 $&'DKDQD\DNH 5/+/5DMDSDNVH Thiessen RESULTS AND DISCUSSION DYHUDJH UDLQIDOO FRQ¿UPLQJ WKH FDWFKPHQW FKDUDFWHULVWLF RI KDYLQJ KLJKO\ UHJXODWHG ÀRZV RZLQJ 5DLQIDOOVWUHDPÀRZDQDO\VLV WRWKHVWRUDJHH൵HFWRIWKHSOHWKRUDRIUHVHUYRLUVLQWKH catchment. Further, the time of concentration for the Figure 2 represents the variation of the catchment FDWFKPHQWZDVIRXQGWREHKRXUVIROORZLQJ3RQUDMDK UHVSRQVH WRWDOGDLO\RXWÀRZIURPWKHUHVHUYRLUFDOFXODWHG 7KHDQQXDOUXQR൵FRH൶FLHQWYDULHGIURPWR from the collected reservoir operation data) with the 0.27 within the study period. )LJXUH 7KLHVVHQDYHUDJHGDLO\UDLQIDOODQGWRWDOGDLO\RXWIORZIURPWKHUHVHUYRLU Figure 2: 7KLHVVHQDYHUDJHGDLO\UDLQIDOODQGWRWDOGDLO\RXWÀRZIURPWKHUHVHUYRLU )LJXUH 5HVXOWV RI WKH \LHOG DQDO\VLV D DQQXDO GHPDQG DQG VXSSO\ FXUUHQW VLWXDWLRQ Ϯϯ E Figure 3: YHULILFDWLRQRIWKHUHVHUYRLURSHUDWLRQVWXG\PRGHORXWSXWVZLWKWKHDF 5HVXOWVRIWKH\LHOGDQDO\VLV D DQQXDOGHPDQGDQGVXSSO\FXUUHQWVLWXDWLRQ WXDORSHUDWLRQDOGDWDFXUUHQW E YHUL¿FDWLRQRI the reservoir operation study model outputs with the actual operational data - current situation; VLWXDWLRQ F DQQXDOGHPDQGDQGVXSSO\DOWHUQDWLYHFURSSLQJSDWWHUQ F DQQXDO GHPDQG DQG VXSSO\ DOWHUQDWLYH FURSSLQJ SDWWHUQ G YHULILFDWLRQRIWKHUHVHUYRLU G YHUL¿FDWLRQ RI WKH UHVHUYRLU operation study model outputs with the actual operational data - alternative cropping pattern RSHUDWLRQVWXG\PRGHORXWSXWVZLWKWKHDFWXDORSHUDWLRQDOGDWDDOWHUQDWLYHFURSSLQJSDWWHUQ September 2019 Journal of the National Science Foundation of Sri Lanka 47(3) Ϯϰ :DWHUUHVRXUFHVDQGSROOXWHWUDQVSRUWPRGHOOLQJ Water balance/yield analysis in Nachchaduwa sub- According to the water quality test results of the samples catchment that were collected throughout the stream cascade in the wet season (Maha season), the single factor The results of yield analyses are presented in Figure 3. $129$WHVW3YDOXHVIRUWKHXSVWUHDPDQGGRZQVWUHDP The input fertiliser amounts and the uptake fertiliser amounts from the crops were calculated and the variation of total input and total uptake (from the crops) of N in each year (for the years 2008–2011 are shown), in each $6&DUHVKRZQLQ7DEOHDQGWKHVDPHIRU3DUHVKRZQ in Table 3. WEP model results 7KH :(3 PRGHO LV FDSDEOH RI SURYLGLQJ WLPH VHULHV values of water and heat balance as well as water quality and material transport results for each grid, as outputs. The preliminary results pertaining to the hydrological )LJXUH :DWHU TXDOLW\ WHVW UHVXOWV ZLWK WKH VDPSOLQJ ORFDWLRQV Journal of the National Science Foundation of Sri Lanka 47(3) September 2019 Ϯϱ $&'DKDQD\DNH 5/+/5DMDSDNVH )LJXUH :DWHU TXDOLW\ WHVW UHVXOWV ZLWK WKH VDPSOLQJ ORFDWLRQV 0DKD VHDVRQ QLWURJHQ DQG SKRVSKRUXVFRPSRQHQWV Figure 5: Water quality test results with the sampling locations - Maha season (nitrogen and phosphorus components) Table 2: Variation of total input and total uptake of nitrogen (kg) each year in each Agrarian Service Centre (ASC) Total N input (kg) Total N output (plant uptake) (kg) ASC 2008 2009 2010 2011 2008 2009 2010 2011 Siwalakulama 324,040 324,040 324,040 366,344 301,466 301,466 301,466 301,466 Yakalla 50,025 50,025 50,025 66,335 21,817 21,817 21,817 21,817 Galenbindunuwewa 23,097 23,097 23,097 30,503 7,606 7,606 7,606 7,606 Ipalogama 96,114 96,114 96,114 118,686 20,150 20,150 20,150 20,150 Kekirawa 160,630 160,630 160,630 206,742 86,425 86,425 86,425 86,425 Maradankadawala 341,351 341,351 341,351 423,338 273,000 273,000 273,000 273,000 Madatugama 255,009 255,009 255,009 322,782 116,014 116,014 116,014 116,014 Mihintale 839 839 839 1,254 0 0 0 0 Shrawasthipura 162,474 162,474 162,474 216,407 31,487 31,487 31,487 31,487 Anuradhapura 12,627 12,627 12,627 16,760 6,713 6,713 6,713 6,713 3DOXJDVZHZD 399,714 399,714 399,714 465,819 246,264 246,264 246,264 246,264 Thirappane 629,629 629,629 629,629 835,730 472,092 472,092 472,092 472,092 Muriyakadawala 346,154 346,154 346,154 485,063 273,713 273,713 273,713 273,713 Kibissa 122,280 122,280 122,280 128,724 36,038 36,038 36,038 36,038 Total 2,923,983 2,923,983 2,923,983 3,684,488 1,892,784 1,892,784 1,892,784 1,892,784Ϯϲ September 2019 Journal of the National Science Foundation of Sri Lanka 47(3) :DWHUUHVRXUFHVDQGSROOXWHWUDQVSRUWPRGHOOLQJ Table 3: Variation of total input and total uptake of phosphorus (kg) each year in each Agrarian Service Centre (ASC) 7RWDO3LQSXW NJ 7RWDO3RXWSXW SODQWXSWDNH NJ ASC 2008 2009 2010 2011 2008 2009 2010 2011 Siwalakulama 79,099 79,099 79,099 118,254 126,819 126,819 126,819 126,819 Yakalla 12,110 12,110 12,110 18,572 9,472 9,472 9,472 9,472 Galenbindunuwewa 6,010 6,010 6,010 8,929 3,260 3,260 3,260 3,260 Ipalogama 20,115 20,115 20,115 29,349 12,404 12,404 12,404 12,404 Kekirawa 37,879 37,879 37,879 57,287 37,183 37,183 37,183 37,183 Maradankadawala 75,015 75,015 75,015 112,156 116,839 116,839 116,839 116,839 Madatugama 61,150 61,150 61,150 88,319 49,552 49,552 49,552 49,552 Mihintale 242 242 242 393 0 0 0 0 Shrawasthipura 42,663 42,663 42,663 65,104 13,438 13,438 13,438 13,438 Anuradhapura 1,719 1,719 1,719 3,129 3,498 3,498 3,498 3,498 3DOXJDVZHZD 56,315 56,315 56,315 84,219 130,187 130,187 130,187 130,187 Thirappane 116,874 116,874 116,874 202,774 216,837 216,837 216,837 216,837 Muriyakadawala 75,907 75,907 75,907 128,533 117,035 117,035 117,035 117,035 Kibissa 5,490 5,490 5,490 8,210 32,809 32,809 32,809 32,809 Total 590,586 590,586 590,586 925,228 869,332 869,332 869,332 869,332 )LJXUH :(3PRGHOVWUHDPIORZFRPSDULVRQZLWK+(&+06PRGHOUHVXOWV D FDOLEUDWLRQSHULRG Figure 6: :(3PRGHOVWUHDPÀRZFRPSDULVRQZLWK+(&+06PRGHOUHVXOWV E YDOLGDWLRQSHULRG(a) calibration period, (b) validation period Journal of the National Science Foundation of Sri Lanka 47(3) September 2019 Ϯϳ $&'DKDQD\DNH 5/+/5DMDSDNVH 6WUHDPÀRZFRPSDULVRQZLWK+(&+06PRGHOUHVXOWV and troughs of the rainfall graph (Figure 7), implying that the rainfall would induce a washout of the solids, 7KH :(3 PRGHO JHQHUDWHG VWUHDPÀRZ YDOXHV IRU and hence adding them into the streams. The mean ± both calibration and validation periods have been standard deviation, minimum and maximum values of FRPSDUHG ZLWK WKH VWUHDPÀRZ WLPH VHULHV REWDLQHG TSS were: 0.90 ± 4.56 mg/L, 0.11 mg/L and 87.40 mg/L based on the pre-calibrated HEC-HMS model. The in the calibration dry seasons; 4.79 ± 14.88 mg/L, :(3 PRGHO VWUHDPÀRZ YDOXHV DUH PDWFKLQJ ZLWK WKH 0.13 mg/L and 148.57 mg/L in the calibration wet +(&+06 PRGHO VWUHDPÀRZ YDOXHV )LJXUH DQG seasons; 0.76 ± 3.45 mg/L, 0.09 mg/L and 49.94 mg/L the validation period showed better results according in the validation dry seasons; 5.62 ± 20.38 mg/L, WR WKH HUURU FRH൶FLHQWV REMHFWLYH IXQFWLRQV XVHG 0.10 mg/L and 304.57 mg/L in the validation wet seasons, 3HDUVRQ FRUUHODWLRQ FRH൶FLHQW 5 VTXDUHG YDOXH URRW respectively. Therefore, on average, the wet season has PHDQ VTXDUH HUURU 1DVK6XWFOL൵H PRGHO H൶FLHQF\ DERXW ¿YH FDOLEUDWLRQ WR VHYHQ YDOLGDWLRQ WLPHV WKH FRH൶FLHQW DQG PHDQ DEVROXWH SHUFHQWDJH HUURU 7KH dry season value of the TSS in the streams. YDOXHVRIWKHVHHUURUFRH൶FLHQWVIRUERWKFDOLEUDWLRQDQG YDOLGDWLRQSHULRGVDUHVKRZQLQ)LJXUH7KH3HDUVRQ Several water quality studies have been conducted FRUUHODWLRQFRH൶FLHQWVKRZVDEHWWHUDJUHHPHQWDQGWKH focusing on the Nachchaduwa catchment (Wijesundara other objective functions used for comparison purposes et al 3HUHUD et al ., 2014). The temporal indicate reduced correlation, presumably due to minor YDULDWLRQ RI :(3 PRGHO UHVXOWV 71 '1 31 73 non-stationarities in the data series. '3 33 ZHUH FODVVL¿HG XQGHU ORZ ÀRZ SHUFHQWDJH H[FHHGDQFHÀRZUDWHRIWRWDOULYHUÀRZOHVVWKDQ PLGÀRZ SHUFHQWDJHH[FHHGDQFHÀRZUDWHRIWRWDOULYHU ÀRZEHWZHHQDQG DQGKLJKÀRZ SHUFHQWDJH H[FHHGDQFH ÀRZ UDWH RI WRWDO ULYHU ÀRZ JUHDWHU WKDQ DQGKDYHEHHQFRPSDUHGZLWKWKH¿QGLQJVRIWKH previous studies. 7KH FRPSDULVRQ RI :(3 PRGHO UHVXOWV GXULQJ WKH water quality testing period of this study are illustrated LQ)LJXUH)LJXUH LOOXVWUDWHVWKHFRPSDULVRQRI:(3 model results for the entire duration of calibration and validation periods, with the entire duration of the three published results. The three published studies have only measured the water quality as spontaneous measurements, for a shorter duration (only for one-year period), and the water quality parameters under all weather conditions have not been considered (as the sampling has been done once a month LQDOOWKUHHVWXGLHV %XWWKHYDOXHVRIWKH:(3PRGHO results shown are the average of a longer time period (hourly values of all days for a period of four years), and therefore represent a wider and a more reasonable range of values of water quality parameters in the streams. )LJXUH 7HPSRUDOYDULDWLRQRIWRWDOVXVSHQGHGVROLGV D FDOLEUDWLRQSHULRG E YDOLGDWLRQSHULRGHowever, it is evident from Figures 8 and 9, that the Figure 7: Temporal variation of total suspended solids; :(3UHVXOWVDUHUHDVRQDEO\PDWFKLQJZLWKWKHSXEOLVKHG (a) calibration period, (b) validation period results. 7HPSRUDOYDULDWLRQRIUHVXOWV Further, for the N components for both the calibration SHULRG DQG WKH YDOLGDWLRQ SHULRG WKH :(3 ORZ ÀRZ The temporal variation of TSS showed a correlation with values showed the best match with the published results. the Thiessen average rainfall values, with the peaks and The published values are given for , therefore, when troughs of the TSS graph corresponding to the peaks comparing, the DN component IURPି WKH :(3 UHVXOWV ଷ September 2019 Journal of the National Science Foundation of Sri Lanka 47(3) ି ଶ ଷି ସ Ϯϴ ି ଷ :DWHUUHVRXUFHVDQGSROOXWHWUDQVSRUWPRGHOOLQJ ି ଶ VKRXOG EH FRQVLGHUHG 7KH '1 LQ WKH :(3 ORZ ÀRZ published values are given for , therefore, when conditions ranges from 0.0023 mg/L to 3.3177 mg/L FRPSDULQJ WKH '3 FRPSRQHQW IURPଷି WKH :(3 UHVXOWV ସ in the calibration period and in the validation period VKRXOG EH FRQVLGHUHG 7KH '3 LQ WKH :(3 KLJK ÀRZ it ranges from 0.00349 mg/L to 3.6347 mg/L. In the conditions ranges from 0.0337 mg/L to 0.1528 mg/Lି published values, it ranges from 1.05 mg/L to 12.00 in the calibration period, and in the validation period ଷ PJ/ 3HUHUD et al KHQFHWKH:(3UHVXOWVFRXOG it ranges from 0.03198 mg/L to 0.1163 mg/L; whereas EHMXVWL¿HG,QDGGLWLRQWKHPD[LPXP concentration in the published values it ି ranges from 0.004 mg/L to ଷ in Malwathu Oya river has been found toି be 15 mg/L in ଷ 0.13 mg/L (Wijesundara et al KHQFH WKH :(3ି ଶ the month of August, by Zoysa and Weerasinghe (2016). UHVXOWVFRXOGEHMXVWL¿HG+RZHYHUWKHVHPRGHOOHG'3 7KHUHIRUH LW FRXOG EH VWDWHG WKDW WKH :(3 UHVXOWV DUH values are above the threshold value of 0.08 ppm of below the maximum value recorded in the basin and IRU WKH RFFXUUHQFH RI HXWURSKLFDWLRQି 86(3$ ଷି ଶ ସ below the threshold value of 10 ppm for ିdrinking water )XUWKHUWKHYDOXHVRI:(3PRGHOOHG'3ZHUHEHORZWKH ଶ (WHO, 2011). thresholdି of 2 mg/L of for drinking and irrigation ଷ water (WHO, 2011). ଷି ସ )RU WKH 3 FRPSRQHQWV IRU ERWK WKHଷି FDOLEUDWLRQ DQG ି ସ ଷ WKHYDOLGDWLRQSHULRGVWKH:(3KLJKÀRZYDOXHVVKRZ The canals and streams of the adjacent Kala Oya river the best match with the published results. This could be basinି have shown 0.0 mg/L–10.7 mg/L and 0.0–23.4 mg/L ଶ DWWULEXWHG WR WKH IDFW WKDW GXULQJ KLJK ÀRZ FRQGLWLRQV of ( ) and 0.02 mg/L–2.60 mg/L, 0.22–0.66 mg/L of WKH KLJK VWUHDPÀRZ ZRXOG LQGXFH D ZDVKRXW RI WKH ( ), ି respectivelyି (Young et al ., 2009). Therefore, in ଷ ଶ solids, hence most of the particulate nutrients which ERWKଷି )LJXUH &RPSDULVRQRI:(3UHVXOWVWHVWUHVXOWVDQGSXEOLVKHGUHVXOWV 31SDUWLFXODWHQLWURJHQ Figure 8: '1GLVVROYHGQLWURJHQ 71WRWDOQLWURJHQ 33SDUWLFXODWHSKRV&RPSDULVRQRI:(3UHVXOWVWHVWUHVXOWVDQGSXEOLVKHGUHVXOWV 31SDUWLFXODSKRUXV '3GLVVROYHGSKRVSKRUXV WHQLWURJHQ '1GLVVROYHG QLWURJHQ 71WRWDOQLWURJHQ 33SDUWLFXODWHSKRVSKRUXV '3GLVVROYHGSKRVSKRUXV 73WRWDOSKRVSKRUXV 73 WRWDO(a) SKRVSKRUXV nitrogen components D QLWURJHQ - calibration FRPSRQHQWV period; (b) nitrogen FDOLEUDWLRQ components SHULRG - validation E QLWURJHQ period;FRPSRQHQWV (c) phosphorus components - calibration period; (d) phosphorus components - validation period YDOLGDWLRQ SHULRG F SKRVSKRUXV FRPSRQHQWV FDOLEUDWLRQ SHULRG G SKRVSKRUXV FRPSRQHQWV Journal of theYDOLGDWLRQSHULRG National Science Foundation of Sri Lanka 47(3) September 2019 Ϯϵ $&'DKDQD\DNH 5/+/5DMDSDNVH 6SDWLDOYDULDWLRQRIUHVXOWV :(3PRGHOUHVXOWVZLWKDOOWKHSDUDPHWHUVJRYHUQLQJWKH 3 FRPSRQHQWV LQ DOO WKH PDWHULDO WUDQVSRUW FRPSRQHQW The excess fertiliser dispersal (wash out) paths and LQSXW¿OHVZHUHDQDO\VHG7KHLQSXW¿OHVZKLFKKDYHWKH accumulation hotspots (the locations with the highest PD[LPXPVHQVLWLYLW\WRWKHPRGHOUHVXOWVZHUHLGHQWL¿HG FRQFHQWUDWLRQRI1DQG3FRPSRQHQWV RIWKHULYHUVODQG DQGDOOWKH3UHODWHGSDUDPHWHUVLQWKRVHLQSXW¿OHVZHUH FRXOGEHLGHQWL¿HGIURPWKHVSDWLDOYDULDWLRQUHVXOWVJLYHQ varied by ± 25 % to check the model sensitivity. E\WKH:(3PRGHO7KHVHKRWVSRWVDUHWKHFULWLFDODUHDV that would need urgent attention when implementing 7KH SDUDPHWHUV JRYHUQLQJ WKH 3 FRPSRQHQWV LQ WKH best management practices for the fertiliser usage. LQSXW ¿OH ZKLFK UHODWHV WR PDWHULDO PRYHPHQW IRU WKH Further, these hotspots could be compared with the CKDu prone areas in the catchment, to check whether RYHUODQGÀRZ VXUIDFH&FVY¿OH DUH GHFRPSRVLWLRQUDWH they are spatially correlated. IURP VXVSHQGHG 3 WR GLVVROYHG 3 51 VHGLPHQWDWLRQ FRH൶FLHQW .3 DPRXQW RI WKH PD[LPXP DOORZDEOH deposit (S ) and amount of initial deposit (S ). It was 6HQVLWLYLW\DQDO\VLVUHVXOWV max ini IRXQGWKDWIRU'3RQO\WKHSDUDPHWHU51KDGDVLJQL¿FDQW :KHQ FRPSDULQJ WKH :(3 PRGHO UHVXOWV ZLWK WKH LPSDFWDQGWKHRWKHUSDUDPHWHUVKDGQRVLJQL¿FDQWLPSDFW SXEOLVKHGZDWHUTXDOLW\UHVXOWVLWKDVEHHQLGHQWL¿HGWKDW )RU33DQG7351DQG6 max KDGDVLJQL¿FDQWLPSDFWZKLOH 3LVWKHOLPLWLQJIDFWRU7KHUHIRUHWKHVHQVLWLYLW\RIWKH RWKHUSDUDPHWHUVKDGQRVLJQL¿FDQWLPSDFW )LJXUH &RPSDULVRQRI:(3UHVXOWVDQGSXEOLVKHGUHVXOWVIRUWKHHQWLUHGXUDWLRQRIFDOLEUDWLRQDQG FigureYDOLGDWLRQ 9: &RPSDULVRQRI:(3UHVXOWVDQGSXEOLVKHGUHVXOWVIRUWKHHQWLUHGXUDWLRQRIFDOLEUDWLRQ SHULRGV 31 SDUWLFXODWH QLWURJHQ '1 GLVVROYHG QLWURJHQ 71 DQGYDOLGDWLRQSHULRGV 31 WRWDO QLWURJHQ 33 SDUWLFXODWHQLWURJHQ '1GLVVROYHGQLWURJHQ 71WRWDOQLWURJHQ 33SDUWLFXODWHSKRVSKRUXV '3GLVVROYHG SDUWLFXODWHSKRVSKRUXV '3GLVVROYHGSKRVSKRUXV 73WRWDOSKRVSKRUXV D QLWURJHQSKRVSKRUXV 73 WRWDO SKRVSKRUXV D QLWURJHQ FRPSRQHQWV FDOLEUDWLRQ SHULRG E QLWURJHQFRPSRQHQWV FRPSRQHQWV validation period; (c) phosphorus components - calibration period; (d) phosphorus components - validation period FDOLEUDWLRQ SHULRG E QLWURJHQ FRPSRQHQWV YDOLGDWLRQ SHULRG F SKRVSKRUXV FRPSRQHQWV FDOLEUDWLRQSHULRG G SKRVSKRUXVFRPSRQHQWVYDOLGDWLRQSHULRG September 2019 Journal of the National Science Foundation of Sri Lanka 47(3) ϯϬ :DWHUUHVRXUFHVDQGSROOXWHWUDQVSRUWPRGHOOLQJ 7KHSDUDPHWHUVJRYHUQLQJWKH3FRPSRQHQWVLQWKHLQSXW were reasonably matching with the HEC-HMS model ¿OHZKLFKUHODWHVWRPDWHULDOWUDQVSRUWLQWKHULYHUFKDQQHO VWUHDPÀRZYDOXHVDQGYDOLGDWLRQSHULRGVKRZHGEHWWHU ULYHU&FVY¿OH DUH 51.3DPRXQWRIWKHPD[LPXP FRUUHODWLRQ FRH൶FLHQWV 3HDUVRQ FRUUHODWLRQ FRH൶FLHQW allowable riverbed deposit (S max ), amount of initial of 0.6875), establishing the suitability of applying the riverbed deposit (S ini ), suspended condition phosphorus :(3PRGHOIRUWKHDQDO\VLVRIZDWHUUHVRXUFHVLQWKLV GL൵XVLRQ FRH൶FLHQW 33 DQG GLVVROYHG FRQGLWLRQ FDWFKPHQW Journal of the National Science Foundation of Sri Lanka 47(3) September 2019 $&'DKDQD\DNH 5/+/5DMDSDNVH 7KH¿QGLQJVRIWKLVUHVHDUFKZLOOEHXVHIXOLQLGHQWLI\LQJ ,QVWUXFWLRQ 0DQXDO . Hydrologic Engineering Research and for recommending the best management practices Team, International Center for Water Hazard and Risk and for coping with the excess fertiliser/agrochemical 0DQDJHPHQW 3XEOLF :RUNV 5HVHDUFK ,QVWLWXWH ,EDUDNL usage of this catchment in a more pragmatic manner. Japan. Jia Y., Ni G., Kawahara Y. & Suetsugi T. (2001a). Simulation 6LQFHWKH:(3PRGHOKDVEHHQVXFFHVVIXOO\DSSOLHGLQ RIK\GURORJLFDOF\FOHLQDQXUEDQL]HGZDWHUVKHGDQGH൵HFW river basins in Japan, Korea and China in similar studies, HYDOXDWLRQ RI LQ¿OWUDWLRQ IDFLOLWLHV ZLWK :(3 0RGHO the results of this study could also be generalised and are -RXUQDORI+\GURVFLHQFHDQG+\GUDXOLF(QJLQHHULQJ 19 (1): applicable to any similar ungauged basin in this region 43–52. ZLWKUHJXODWHGRUXQUHJXODWHGÀRZV Jia Y., Ni G., Kawahara Y. & Suetsugi T. (2001b). Development RI:(3PRGHODQGLWVDSSOLFDWLRQWRDQXUEDQZDWHUVKHG 15 : 2175–2194. REFERENCES +\GURORJLFDO3URFHVVHV DOI: https://doi.org/10.1002/hyp.275 Jia Y., Niu C. & Wang H. (2007). Integrated modeling and $PHULFDQ 3XEOLF +HDOWK $VVRFLDWLRQ $3+$ assessment of water resources and water environment in American Water Works Association & Water Environment the Yellow River Basin. -RXUQDO RI +\GUR(QYLURQPHQW Federation. 6WDQGDUG 0HWKRGV IRU WKH ([DPLQDWLRQ RI 1: 12–19. st 5HVHDUFK :DWHU DQG :DVWHZDWHU , 21 HGLWLRQ $PHULFDQ 3XEOLF DOI: https://doi.org/10.1016/j.jher.2007.04.001 Health Association, Washington DC, USA. Jia Y. & Tamai N. (1998). Water and heat balances in the %HQQHWW -& 5REHUWVRQ '( :DUG 3*' +DSXDUDFKFKL middle-reach catchment of Tama River and sensitivity +$3 :DQJ 4- &DOLEUDWLQJ KRXUO\ UDLQIDOO analysis. $QQXDO-RXUQDORI+\GUDXOLF(QJLQHHULQJ-6&( UXQR൵PRGHOVZLWKGDLO\IRUFLQJVIRUVWUHDPÀRZIRUHFDVWLQJ 42 : 151–156. applications in meso-scale catchments. Environmental DOI: https://doi.org/10.2208/prohe.42.151 0RGHOOLQJDQG6RIWZDUH 76 (2016): 20–36. Jia Y.W., Kinouchi T. & Yoshitani J. (2005). Distributed DOI: https://doi.org/10.1016/j.envsoft.2015.11.006 hydrologic modeling in a partially urbanized agricultural Cash D., Melton B., Gregory J. & Cihacek L. (1981). ZDWHUVKHG XVLQJ :(3 0RGHO -RXUQDO RI +\GURORJLF 5KL]RELXP,QRFXODQWVIRU$OIDOIDLQ1HZ0H[LFR (Research (QJLQHHULQJ 10 : 253–263. Report 461). New Mexico State University Agricultural .DPUDQ0 5DMDSDNVH5/+/ (൵HFWRIZDWHUVKHG Experiment Station, Las Cruces, USA. subdivisions and antecedent moisture condition on HEC- Cunwen N., Yangwen J., Hao W., Zuhao Z., Yaqin Q., Shjun HMS model performance in the Maha Oya Basin, Sri Lanka. B. & Caixia L. (2011). Assessment of water quality under 3URFHHGLQJV RI WKH th ,QWHUQDWLRQDO September 2019 Journal of the National Science Foundation of Sri Lanka 47(3) :DWHUUHVRXUFHVDQGSROOXWHWUDQVSRUWPRGHOOLQJ :(3DQGDQHURVLRQWUDQVSRUWPRGHO :DWHU3UDFWLFHDQG concentrations in water in the Thirappane Tank cascade 7HFKQRORJ\ 5(3): wpt2010051. in dry zone of Sri Lanka. Journal of Environmental DOI: https://doi.org/10.2166/wpt.2010.051 3URIHVVLRQDOV6UL/DQND 1(1): 70–81. Silva E. (2004). Quality of irrigation water in Sri Lanka - status DOI: https://doi.org/10.4038/jepsl.v1i1.5143 and trends. $VLDQ -RXUQDO RI :DWHU (QYLURQPHQW DQG Wijesundara W.M.G.D., Nandasena K.A. & Jayakody A.N. Pollution 1(1): 5–12. 6HDVRQDODQGVSDWLDOYDULDWLRQVRI13.DQG&G 8QLWHG 6WDWHV (QYLURQPHQWDO 3URWHFWLRQ $JHQF\ 86(3$ concentrations in water of the Mahakanumulla cascade in (1976). 4XDOLW\ &ULWHULD IRU :DWHU . United States the dry zone of Sri Lanka. 7URSLFDO$JULFXOWXUDO5HVHDUFK (QYLURQPHQWDO3URWHFWLRQ$JHQF\:DVKLQJWRQ'&86$ 24 (3): 279–288. 8QLWHG6WDWHV3HDFH&RUSV 8QLWHG6WDWHV3HDFH&RUSV DOI: https://doi.org/10.4038/tar.v24i3.8013 ,QIRUPDWLRQ&ROOHFWLRQDQG([FKDQJH (Online). Available World Health Organization (WHO) (2011). *XLGHOLQHV at: KWWS ZZZQ]GORUJJVGOPRG"H GRৼFGO IRU 'ULQNLQJ :DWHU 4XDOLW\ , 4 th edition. World Health GLUHFWOHQ Organization, Geneva, Switzerland. DERXWXWI=] D Journal of the National Science Foundation of Sri Lanka 47(3) September 2019