Sep 17, 2010 - ... obtained roof runoff coefficients for commonly used asbestos, Tiles ...... of pilot testing phase, lack of investments for activities proposed for ...
Surface Water Resources and Climate Change N.T.S. Wijesekera Professor in Civil Engineering University of Moratuwa, Sri Lanka
Introduction Water accumulated or flowing on the surface of earth is considered as surface water. The water on the surface can originate from rains or from groundwater. Surface water resource is that part of the surface water stock which can be drawn on for various uses of water. In order to be aware of surface water resource, it is necessary to understand the magnitude, quality, and status with respect to spatial and temporal occurrence, ownership, allocations etc. Therefore research on surface water resources would require searching for knowledge or carrying out systematic investigations to establish facts about surface water. It is often necessary to identify limits of search and this depends on the users of the facts about surface water. In case of an abundant surface water resource, one might be satisfied with facts having only the order of magnitude, but when the resource is scarce, it is very important to dig deeper to seek detailed facts. This surfaces the need to conduct good research. The key to good research is systematic investigations in order to establish facts which would in turn enable either establishment of a present practice or understanding the need for improvement of a present practice. Climate change impacts are a key area of concern especially when water is the underlying theme. Though there is a factor of uncertainty about the potential climate change and its impacts, anticipated challenges from climatic change including the changes to precipitation and its pattern, changes to irrigation demands, changes to soil moisture due to temperature variations, changes to quantities evaporated from irrigated lands and irrigation reservoirs have been reasonably recognised. There is a higher confidence in projected patterns of warming and other regional-scale climate change features, including changes in wind patterns, precipitation and some aspects of extremes1. It is projected that crop yields could decrease up to 30% in Central and South Asia by the mid-21st century. Taken together and considering the influence of rapid population growth and urbanisation, the risk of hunger is projected to remain very high in several developing countries2. It is also stated with very high confidence that water resource in many small islands is likely to be seriously compromised. As a result of climate change such islands are likely to experience water stress and predictions show reduced rainfall in summer. Hence it is unlikely that demand will be met during low rainfall periods. Increased rainfall in winter will be unlikely to compensate, due to a lack of storage and high runoff during storms3. The present work targets to identify and assess the research work that had been conducted on surface water and climate change of Sri Lanka through a review of selected literature. In case of assessing research, an important issue is to identify the reliability of results. Good research is expected to contain independent, objective results and analysis, which reflects reality. A research result to be reliable, a reader should be provided with a clear description of the used data and the quality of such data, along with an adequate description of the research methodology used for data collection and analysis. A good research would provide evidence of referencing thereby building reader confidence with respect to the sufficiency of
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background work4,5. The present review is an attempt to capture the adequacy of surface water resources and climate research and associated reporting in a responsible manner. Surface water resources research In Sri Lanka there had been a considerable interest generation in water resources research during the International Hydrological Decade and the International Hydrological Programme but it appears that there had been a lack of publication opportunities6. The said literature also indicates that in the late 1970’s consultancy reports had become a common medium of conveying water research findings, while the hard and fundamental research activities were from the universities and research institutions. A survey carried out using a sample of 62 knowledgeable persons as reported by Madduma Bandara6 (1998) had identified that the most important topics for water related research were related to policy, planning and institutional issues. In order to carryout a review of surface water research it is necessary to identify its subsections. A survey of commonly used titles and terminologies lead to the identification of the sub sections for this review as, research on surface water resources, surface water, floods, streamflow, rainfall, water quality, storage systems, and research on water policy and strategy. Research on surface water resource, surface water resources modelling, catchment yield, droughts, and lowflow studies were grouped under surface water resources research. Under the surface water research title, research on surface water assessments in watersheds, surface runoff coefficients, surface water infiltration and seepage, surface water evaporation, surface flow rating curves, surface water extractions, surface water conservation, surface water development-potential estimation, surface water economics, surface water and wetlands were grouped. Research on flood estimation in gauged catchments, flood estimation in ungauged catchments, flood modelling, recurrence Intervals and flood frequency, surface water, drainage and canal network etc., were grouped under the title of floods. Research on streamflow estimation in ungauged catchments, streamflow estimation in gauged catchments, flow measurement, flow measurement network, river network identification, assessment, development, and environmental flows were categorized under the title of streamflow. While research on rainfall trends, loss rates and probable maximum precipitation were grouped under rainfall research, surface water quality, measurement water quality measurement network research and water quality modelling were grouped as water quality research. Research on small and medium tank systems, reservoir storage, seepage, releases, reservoir operation, reservoir mapping, networking, monitoring, assessments were labeled as surface water storage systems research. Research on multiple use of surface water, water user association and institutes, water policy, water pricing, training and human resource development are categories that were grouped as water policy and strategy research. Climate change related research Review of climate change related research under the main theme of water resources was done by identifying research on climate linkages with rainfall, evaporation, water use, surface water storage, irrigation, hydropower, drinking water, wetlands, water quality, floods and drainage, environmental flows, soil moisture, temperature and forest cover forming a single group.
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The present work reviewed 91 selected publications on surface water and climate change pertaining to Sri Lanka and they were summarized to highlight the key information provided with the publication in order to ascertain the value of research. Among other things, major and secondary thematic areas, spatial and temporal resolutions, study area locations, study period, techniques, data and data checks, and issues of concern were extracted from publications. Majority of the reviewed research papers did not have most of the key information desirable for a reasonable assessment. Summary of reviewed papers. Water resources 1. In Amarasinghe, Mutuwatte and Sakthivadivel (1998, 1999)7,8 district level water supply and demand analysis has been made and the author s have assessed the water resources, contributions to runoff and water withdrawals under various assumptions and scenario to reflect the spatial distribution of water scarcities. The work compared various definitions of water scarcity and reports the estimated results for 1991 on a seasonal basis analysis along with a future scenario assessment using a different method to compute the net inflows and surface runoff. This work reports a difference of water scarcity values compared to national level statistics and emphasizes the need for a better spatial and temporal analysis of water inflow, runoff and withdrawals under an acceptable water scarcity scenario. These have been indicated to include better rainfall runoff relationships, reliable storage assessments and efficiency estimates. Results indicate that total utilizable water resources per unit area in districts range from 0.03 meter to 1.43 meters in Maha season and from 0.02 meters to 1.7 meters in Yala season. 2. Rainwater harvesting capacity computation for Moneragala District has been carried out through a survey of water demand and water use by householdes9. The study has revealed that a capacity of 23000 liters is needed for the dry zone and 16000 liters for the intermediate zone to avoid water scarcity. Report indicates the use of a model for roof water balance and a statistical package for data analysis. The recommendations describe factors connected with rainwater harvesting technology application. 3. Imbulana (2000)10 identifies the major issues associated with the development of water resources for irrigated agriculture, the challenges emerging from those issues and available options to face such challenges. This paper while stressing the need to efficiently use the already developed water resources, indicate that there is also a need to develop additional water sources as well. The paper highlights demand management requirements through the management of competing users and through performance enhancements for effective management of the available surface water resources. 4. Manchanayaka, Madduma Bandara (1999)11 in a monograph on water resources of Sri Lanka provides details on surface water, usage and potential for development, and lists 64 bibliography documents. The authors indicate that this work is not a complete reference work on the title but an attempt to provide a general coverage of the most important aspects. 5. Smakhtin and Weragala (2005)12 discusses about the attempts made to carryout the assessment in Walawe river and the difficulties faced in the absence of reasonable daily time series data. Methodologies are presented to compute under data scarce situation and makes recommendations to strengthen the water resources assessment in Sri Lanka.
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6. Wickramaarachchi (2004, 2010)13, 14 studying water resources in the Deduru Oya basin using monthly data had identified a significant spatial variation of surface water resources in the basin along with a significant temporal variation of the runoff coefficient in the lower basin. This work reported as a preliminary assessment of the surface water resources of Deduru Oya at two gauging locations namely the Rideebendi Ella and at Chilaw using monthly data of 1970-1979 and 1990-1998. This study has used 10 rainfall station data representing agroecological regions, Pan evaporation data of Batalagoda, Lunuwila and Peradeniya. Data checking had indicated the absence of continuous data for any rainfall, river gauging and evaporation stations. Station densities had been checked for WMO standards and found satisfactory. Rainfall and Runoff coefficient study had revealed that the upper catchment runoff coefficient is consistent but for the lower catchment the coefficients are on the high side indicating an over estimation of runoff. It is suggested that this may be an effect of the sea and the flatness of the terrain. 75% probability data for the two gauging stations considering 16 years for Rideebendi Ella and 9 years for Chilaw are presented. 7. Wickramasuriya (1996)15 in this paper discusses the observations and experiences along with certain hypotheses with respect to the water and related development works carried out in the past and present. This paper indicates that there may be problems in the proposed diversion of Kaluganga water to Southeast dry zone, issues in the filling of Muthrajawela, cautions about the state of imbalances in the boundary conditions between the land and the sea, suggests that the collapse of irrigation system in the 12th and 13th century to cyclonic storms, hints about nature’s reactions to Nilwala Ganaga Diversion at Urubokka, and cites the need of augmenting groundwater and then to harness for irrigation. 8. In order to identify a relationship between the temporal variation and response characteristics of the Kalu Ganaga catchment, the storage characteristics of the catchment is investigated in this paper16. The paper indicates the possibility to forecast long term discharge using this model. In this work daily rainfall and runoff data from 1980 to 1990 were investigated and representative years had been selected for model calibration and verification. The results indicate that all sub basins of Kalu Ganaga possesses an evapotranspiration rate of 525 mm/year. The work indicates that the sub basins possess two types of response characteristics or unit graphs within a year, which do not vary appreciably from sub basin to sub basin, and that the results were investigated for high and low rainfalls showing the usefulness and accuracy of the model. 9. In this study Hunukumbura, Weerakoon and Herath (2004a)17, flow duration curves are developed for long term forecast of daily Streamflow by the Tank model which is calibrated for each basin using one month daily rainfall, evaporation and streamflow. The work is an application to Talawakelle, Calidonia and Huluganga basins. It is stated that the flow duration curves developed from the forecasted streamflows have been compared with those of observed streamflows pertaining to a six year period. The indicated for comparison of modeled and observed flows had been the plant factor. 10. In Mungai et al (2004)18, a long term hydrologic study of Nilwala Basin has been indicated using daily discharge at the Bopagoda gauging station from 1940-1997recorded by the Irrigation department, daily rainfall for the stations within the watershed recorded by the Meteorology Department and land cover data interpreted from areal photographs
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and stakeholder surveys. Long-term trends in seasonal and annual rainfall and streamflow had been analyzed using moving averages and linear regression models. Variations in annual runoff have been compared with variations in rainfall and land use. Land use transformations coupled with the reduction in forest cover from 50 to 30% during the 1940–1964 period has shown an increased runoff. Between 1948 and 1964 mean annual runoff has increased by 11% or 17.5 cm when compared with the 1940–1947 period and this has been attributed to increased baseflow. Authors had indicated that this increase could be due to reduction in transpiration. 11. Nandalal and Sakthivadivel (2003)19 has carried out an annual water accounting of the Walawe river basin (2442 sq km) based on a water balance approach for the period from 1994 to 1999. The indicator selected is termed as depleted fraction. Study has identified that for the Samanalawewa catchment, 53% of the water is available for downstream use. The average annual amount of utilizable water that leaves the Walawe river basin without being used has been estimated at 926x106 m3 while the data of Liyangastota weir indicates that annual Walawe river discharge is about 450x106 m3. According to the paper, after extension of the left bank irrigation area the quantity of water that would discharge from the catchment without use amounts to about 31% of the water available in the catchment. 12. Wijesekera (1999b)20 presents and assessment of streamflow for the Upper Kotmale Hydropower project for a comparative assessment of two project alternatives using gauged data of Talawakele in the Kotmale Oya for the period between 1950 and 1990. The research revealed a clearly visible variation of rainfall and streamflow average values for the study period. Also it has been identified that there is a significant difference in the project specific and irrigation department developed rating curves. The results discusses the need of checking observed streamflow data and rainfall data prior to deriving results to evaluate benefits from surface flows. 13. Wijesekera (2000a)21 in this work for Gin Ganga watershed at Thawalama had carried out monthly streamflow modelling using different datasets and optimization methods. Evaporation data of one station for 6 years (1986-1991), rainfall of four stations for at least 26 years (1949-1985) and streamflow records for 10 years (1972-186) had been available for the study. Data checking had been carried out using annual water balance, double mass curves, plots of Thiessen rainfall and plots of streamflow. 1974-1976 period had been used for model calibration and years 1980, 81 and 84 had been used for verification of model outputs. Optimisation of parameters had been done using a manual method and a semi automatic method using a computer program developed to incorporate a specific search method. The model outputs had been compared using numerical indicators, streamflow hydrograph observations, flow duration curves and annual water balance. The paper has indicated that the interchange of datasets for calibration and verification had shown that there had been no significant changes in the parameters and outflow hydrographs. The semi automatic search had produced a faster and better search over the objective function surface resulting in a superior set of parameters reflected by the outflow hydrographs. The paper mentions the importance of assess model outputs using visual comparisons, numerical indicators, water balance and duration curves to obtain realistic parameters. 14. In this study Wijesekera and Ghanapala (2003)22 have modeled two watersheds one at Torrington and the other at Attidiya using 15 minute interval rainfall and streamflow data.
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Watershed model had used the HEC model with AMC class II condition and associated runoff curve numbers had been taken from literature for initial approximations. The paper presents the optimized runoff curve numbers for each catchment and weighted curve numbers for respective catchments enabling the reproduction of hydrographs for water resources assessments. 15. Wijesekera et al (2005)23 briefly describes the use of a conceptual hydrologic model with a three linear reservoirs used to model the Mee Oya watershed using monthly data and the surface runoff predictions for 75% probable rainfall. 16. Wijesekera(2001)24 in this work has carried out a water balance study of the Mahaweli Watershed at Peradeniya using a daily conceptual mathematical model has indicated the catchment response to rainfall by generating surface water and contributing to storage. 17. Chandrasekera (1999)25 proposes a method for derivation of rainfall-catchment yield correlation factors that are unique to a particular catchment by analyzing historical rainfall and riverflow data. The proposed method is a trial and error manual process leading to derivation of simple equations with coefficients of correlation with antecedent rainfalls. The paper mentions that application requires continuous data sets of rainfall and Streamflow for at least 3-5 years should be available and the time step should be taken as one week for diversion schemes and one month for reservoir schemes. The paper has mentions of three test case studies and the parameters of correlations derived from the application for 3-4 year datasets. Paper has indicated the unavailability of an adequate number of river gauging to cover the entire country and the non availability of a standard procedure at the Irrigation Department to release river flow data as limitations that preclude further studies on this method. 18. Navaratne and Weerasinghe (2004)26 had carried out field experiments at Mapalana research farm and obtained roof runoff coefficients for commonly used asbestos, Tiles and Cadjan roofs as 0.84, 0.75 and 0.65 respectively. These coefficients enable the identification of reservoir sizes for rainwater harvesting. 19. Manchanayaka (1996)27 in a study of hydrological characteristics of the Mahaweli and its Development area, had indicated the use of published monthly rainfall data covering 22 districts and for the period 1896-1975. Rainfall for serven districts had been extracted from this data set to contain about five raingauge stations from each district with consistent and reliable records. Yala and Maha seasonal rainfalls had been computed for the 80 years. Rainfall runoff relationships had been obtained by the Irrigation Department hydrologic annuals. The variability characteristics of rainfall, frequency of occurrence of droughts, monthly distribution of rainfall and runoff-rainfall relationships have been studied in this work. The results have shown that Pollonnaruwa and Anuradhapura were facing water shortages or droughts at average frequencies of once in 2.9 years and 3.8 years respectively in the Yala season before the drought. Also droughts occurring in successive years had been studied. The study indicated that it had proven Mahaweli area could be categorically divided into two hydrological regions, namely the catchment area above Polgolla and the area below Polgolla including entire area of development. A comparison of definitions of drought had been carried out in the study. 20. Dharmasena (1999)28 in this work has studied 11 small up country catchments having annual rainfall of 2000mm to 5000 mm and area varying from 10 sqkm to 100 sqkm to
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discuss the procedures to be adopted in lowflow frequency analysis. The work makes an attempt to correlate the low flow characteristics of streams with climatic and other physical properties of the catchments. 21. Objectve of Hewa and Peel (2004)29 has been to demonstrate a recently developed low flow frequency analysis technique that utilizes the Truncated Generalised Extreme Value (TGEV) distribution. The work with utilized the annual minimum daily flow series has studied the Ginganga at Agaliya using daily data from 1928 to 1989 with few years excluded due to long periods of missing data. Data filling has been carriedout for less than 2% of the total records, where missing data were not in the low-flow season and where the missing period was as short as several days. It has been indicated that the TGEV is a suitable distribution function for low flow frequency analysis in monsoonal regions. Surface water 1. Manchanayaka, Wickramasuriya and Ekanayaka,(1987)30 modeled the Uma Oya catchment to predict the surface runoff using 11 years of consistent data from 1959 to 1969. The linear regression model using monthly rainfall data of nineteen stations and two flow monitoring stations at Welimada and Thalawakanda The model has been developed using the 11 year data and then the error in prediction has been computed for the same set of data. 2. Bandara (2003)31 using 10 day composites of NOAA satellite data, digital maps of ancillary data and boundaries, reservoir water issues and rainfall data for 1999, has computed the evaporative fraction, daily potential and actual evapotranspiration etc., leading to the computation of productivity of water in three large irrigation schemes namely, Polonnaruwa, Kirindi Oya and Gal Oya. Paper presents the computed values of water productivity in Polonnaruwa and Gal Oya as 0.29 and 0.40 kg per cubic meter of water inflow respectively. 3. Bandara (2006)32 in his work has used modern satellite remote sensing information on a daily basis and at a spatial resolution of 250m to 1000m. The 10 day interval study had been carried out for the Uda Walawe and Liyangastota Irrigation Schemes using computations done for the identifications of relative evapotranspiration, delivery performance, depleted fraction, and drainage ratio. The study reports that under stressed conditions the actual evapotranpiration derived from 1000mx1000m MODIS data deviated 10% from those derived from the 30mx30m Landsat Data. Under normal situations where actual evapotranspiration could be equaled to potential evapotranspiration this deviation had been reduced to only 6% and below. The author concludes that MODIS data had shown to provide information with sufficient accuracy if the irrigated area is greater than 2000 ha. The report presents monthly rainfall of 6 stations used for the study, actual and potential evapotranspiration at Liyangastota for 2002-2003 derived from remote sensing data, canal discharges, and 10 day interval water productivity for Liyangastota and Uda Walawe. 4. Gunawardena (1998)33 describes the application of a water use model to determine the impacts of different land use on water demand carried out to investigate the possibility of manipulation of evapotranspiration loss through land use management. This work carried out for hydrological years from October 1994 – September 1996, presents the
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instrumentation, land use monitored, types of data collected, and the major findings with respect to water use percentages of various canopy status and soil depths. The work indicates the need of a simulation model which accounts for local climate, physiographic, vegetation and soil variations for assessment of impacts of land use variations on water use. 5. Jayathilleka (2007)34 has compared the Penman Monteith ET0 values with potential evapotranspiration (PET) and modified Penman ET0 values using monthly average temperature, humidity, sunshine hours wind velocity values measured at Maha Illuppallama meteorological station during the period from 1976-2004. None of the methods have showed a significant difference on reference evapotranspiration values under the experiment. The authors have recommended the use of Penman Monteith ET0 values for future work. 6. Wijesooriya (2005)35 in this work quotes the availability of surface water from rainfall, spatial variability of runoff and rainfall according to administrative districts, hydrometric network of country, rainfall runoff ratios, wetlands and drainage, floods and droughts, surface water withdrawals, extractions and usage, and water balance of watershed zones quoting from various reports and discusses the need of a well defined, and accurate data and information system to reflect the island’s heterogeneity corresponding to micro climate, agro ecology and for various micro catchments. This paper indicates the need of a centralized information system with precise and correct, water resources, flood and drought information. Floods 1. De Costa (1999)36 describes a comparison of flood forecasting model applications using the Nilwala basin as the study area. Daily data for the years 1986 to 1993 pertaining to Streamflow at Pitabeddara and Bopagoda, Rainfall and evaporation data of Goluwawatta and Kottawa had been used. A simple linear model, linear model, linear perturbation model, soil moisture accounting model, and variations of the single and multiple input series, simple linear model and linear perturbation model are also applied. Calibration and verification has been done for 1986-1990 and 1991-1993 periods respectively and model efficiency has been calculated according to Nash Sutcliffe criteria. Reported conclusions are, linear perturbation models performed better than simple linear models in all cases, multiple input series performs better that the single input case, and conceptual models do not perform as well as the said models. 2. Wijesekera (2000b)37 had carried out a comparison of peakflow estimation methods for eight small urban catchments having sizes varying from 4 ha to 35ha selected from a set of 20 catchments draining in to the Colombo Port. The methods used have been the Rational method, HEC, SCS and Snyder’s Unit Hydrograph models. The sensitivities of model estimates had been studied and it had been identified that the variation of estimates was of significant difference when the watershed area becomes larger. Estimation of Time of Concentrations had shown that the valued obtained using actual field identified drainage paths and sizes were of much lesser value than the values from frequently used empirical values. Runoff coefficients computed from three methods had shown that a common value can be identified for the Colombo harbour. The study indicates the lack of observed streamflow values had prevented from a comparison of modeled outputs with the actual.
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3. Wijesekera and Abeynayake (2003)38 had carried out a study of annual peakflow of four main watersheds in the Kelani, Kalu, Gin and Nilwala river basins in the wet zone to analyze the feasibility of transposition. The study has established a Peakflow Similarity Index and three main criteria relating rainfall, shape and slope which could be effectively used to identify similar watersheds for peakflow transposition. The work which used monthly Streamflow, rainfall and annual peakflow records from 1940 to 1985 has identified that annual peakflows of similar watersheds can be transposed satisfactorily with the relationship that peakflow from a watershed is proportionate to the 0.8th power of its area. 4. Dharmasena (1992b)39 in his work has targeted to enhance the understanding and application of recent developments in mathematical modelling technique for flow simulations. Six and five principal-rainfall station daily-datasets respectively for Kaluganga at Ellagawa and Kelani Ganga at Glencourse with daily streamflows and evaporation values had been used in the study. In Kalu Ganga and Kelani Ganga 3 and 6 years of data respectively had been used for model calibrations while respectively, 2 and 4 years of data had been used for verifications. This work presents the application of six models varying from seasonal, linear to conceptual. the author among other things had concluded that in case of Kelani and Kalu, linear models can be used satisfactorily instead of complicated conceptual models, most models produce similar results, and lower efficiency of model out puts have been found in the Kelani ganga due to longer period of calibration. The author had commented about the lack of availability of streamflow data and had stated that forecasting of surface flows during floods or droughts is still at its infancy. The validity of the streamflow data under the changing land cover and the lack of instrumentation has also been discussed. 5. Dharmasena (1997)40 had studied linear black box models and conceptual models. Linear Blackbox models have shown better performance in case of wet zone basins. Conceptual models have been recommended for dry zone basins. Indicates poor quality evaporation data is an issue and also that it is necessary to investigate the validity of some optimized parameters. Recommends further verifications of input data and modifications to the model parameters before using for real applications. Indicates the need to interface hydrodynamic models to represent lower parts of the basins. 6. Nandalal (2009)41 had carried out a comparative assessment of HEC-GeoHMS and HECHMS models for the Upper Kalu Ganga Catchment of 622 km2 had used time to peak, peak discharge, and total runoff volume for assessment. Results had indicated reasonable close reproductions by both models suggesting the applicability of simpler lumped model. Study had used weather data, and on line GIS data. 7. Dharmasena (1992a)42 has analysed the rainfall on the 5th June 1992 and commented on the magnitude, depth duration frequency curves, frequency analysis, and frequency of design floods. When analyzing extreme events of rainfall it is recommended to consider the rainfall in a region, instead of point rainfall at a specific site. It is also recommended to identify areas to be protected in terms of a selected design return period. The study recommends that the Colombo canal rehabilitation project report developed for implementation needs updating keeping in line with the flood experienced by the Colombo Flood.
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8. Fernando (1989)43 in his work has dealt with a study of annual maximum floods in the Kelani Ganaga and the derivation of a Regional Flood Frequency Curve using 10 gauging stations having 10 years of continuous records. It is indicated that data had been checked for available record length and accuracy. Lack of continuous data due to washing away of gauge posts, due to reduced frequency, and some inaccuracies have been indicated as limitations. The paper presents a regional flood frequency curve for the Kelani Ganga Catchment area and recommends further work to cover the entire island. 9. Gamage (2002)44, in his work has applied regionalization technique to Kitulgala catchment in Sri Lanka and demonstrated the result in the identification of region that is effective for the estimation of extreme quantiles in the context of regional flood frequency analysis. A regionalization strategy is developed and demonstrated through application to a collection of catchments in Sri Lanka. 127 catchments had been screened and 68 had been selected with at least 10 years of observations, containing 1564 records within the period between 1940-1985. From the dataset 46 unregulated catchments had been selected for analysis. It has been reported that there is a homogeneous region of interest with 6 sites for Kitulgala. The authors indicate that the selected record length is not to signify that a 10 year period provides reliable results. Further it is stated that the work demonstrates work for gauged catchments and it is important to carryout similar studies for ungauged catchments. 10. Manchanayaka (1998)45 in this study has calculated the recurrence frequency and recurrence frequency in succession for droughts and floods had been calculated using data of 80years extracted from literature. Evaporation for Hambantota had been computed using Penman using meteorologic data and pan evaporation data The lake evaporation has been computed using co-axial graphical technique. Using river flow records for the 30 years from 1944 to 1973, specific yield and runoff rainfall ratio had been computed for five river basin locations. The study has revealed that the lowest specific yield and lowest runoff/rainfall ratio is at Kataragama in Menik Ganga. The study recommends identifying suitable methods to reduce lake evaporation at Hambantota which has been indicated as greater than average annual rainfall with suitable testing. It has been indicated that the validity of the results need to be checked with recent data. 11. Wijesekera (1999)46 describes recommendations for simple low-cost engineering solutions for the development plan of a 23.5 ha industrial estate at Dankotuwa using available design guidelines. Study using a 2 year design storm period has incorporated a water balance study to recommend typical values for spatially distributed detention/retention facilities to control surface water runoff. 12. Attygala and Wijesekera (2006)47 in this study has carried out work to generate stream network in GIS using data extracted from areal photographs, to assess the accuracy with surveyed drainage network and then to identify parameters that affect the accuracies. The study area had been two urban watersheds from Colombo (450ha and 190 ha) and one from Moratuwa (250 ha). The study had identified that the accuracy levels were lower in the areas of lower stream order hinting that the streamlines would vary either due to the low contributing cells or as a result of human interventions after the surveyed data that had been used. The study concludes that stream network identification to a reasonable accuracy using remotely sensed data of 0.4m accurate contours and additional spot heights is not a straightforward operation in the case of selected watersheds and that the significant flat terrain poses problems in identifying the flow directions to find a
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unique stream network. Study indicates the use of remotely sensed image mosaics, digital terrain data and study specific GPS measurements as that used for the study. Streamflow 1. In this work Wijesekera (1999a)48 has carried out extrapolation of gauged adjacent Deraniyagala catchment data to the ungauged catchment Bopath Ella. Missing flow data of the catchment had been filled using a mathematical watershed model based on the Sugawara’s Tank Model. Daily flow duration curve at Bopath Ella was used to estimate the appropriate water releases. Daily streamflow data for the period 1955-1978, Monthly evaporation data for the 1990-1994 period and rainfall between 1971 and 1996 had been available for the study. The work has included data checking, filling and mathematical modelling of the Deraniyagala. The study concludes with the introduction of an exptrapolation technique and the use of a simple hydrologic model for estimating the missing data with model calibration and verification. In this study the similarity conditions had been explicitly quantified and daily flow duration curves from 1955 to 1978 had been used to estimate the downstream water releases. 2. Hunukumbura, Weerakoon and Herath (2004b)49 has applied a physically based, conceptual and a black box model for the Upper Kotmale Basin (304 sq km) using daily data for the period from 1987-1993 with 1987-1988 as the calibration period and the rest for verification. Quantitative comparison of performances has been made with the use of standard deviation and value of mean flow, Nash-Sutcliff coefficient and the root mean square error. It has been found that the conceptual Tank model forecasted the streamflow to best level with the other two models showing similar accuracies. 3. Premathilleka, Perera and Weerakoon (2004)50 reports the application of two Multiple Linear Regression Models for the Upper Kotmale catchment at Thalawakele using daily Streamflow, rainfall and evaporation. The two models, a Multiple Linear Model and a Segmented Multiple Linear Model has R-squared values of 0.5842 and 0.8060 respectively once the outliers were removed from the dataset. 1987-1990 period has been used for Calibration while 1991-1993 period has been taken for verification. 4. Weragala and Smarktin (2004)51 examines the performance of two streamflow modelling methods under conditions of limited data by applications in the Rakwana Oya catchment of Walawe Basin using daily data from 1990 to 1994 for calibration and 1995 to 1997 for validation. One method was the use of Soil and Water Assessment Tool (SWAT) and the other was the use of non-linear spatial interpolation method. Outputs have shown superior coefficient of determination for the SWAT model while the Coefficient of Efficiency is in the same range for both models. The study has used land and land use spatial distribution, rainfall of three stations, climatic data from Sevanagala Sugar Research Institute, and steamflow data from the irrigation department. It has been stated that due to the intensive data requirement of SWAT model suggests that application to bigger catchment like Walawe Basin is not feasible, whereas the Spatial Interpolation Method can perform satisfactorily and hence used to simulate non-regulated river flows in small and big basins. 5. Wijesekera and Musiake (1990a)52 had used daily rainfall of 4 locations and streamflow at Peradeniya, from 1969-1980 and daily evaporation data of two stations from 19781986 to calibrate and verify Sugawara’s Tank model for catchment at Peradeniya where
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model parameters and also the rainfall station weights had been optimized. The Ratio of Absolute Error to Mean during the calibration and verification had been reported as 0.2733 and 0.2399 respectively. 6. Wijesekera and Musiake (1990b)53 had used daily rainfall of 6 locations and streamflow at Putupaula, from 1972-1979 and daily evaporation data of two stations from 1978-1983 to calibrate and verify Sugawara’s Tank model with a flood tank, for catchment at Putupaula where model parameters and also the rainfall station weights had been optimized. The study indicates an improvement in the Ratio of Absolute Error to Mean value to 0.2667 after the incorporation of a flood tank and the spatial variability of rainfall. The study results state that in the mathematical model the evaporation data indicated a marginal effect. 7. Herath, Ratnayake & Weerakoon (2007)54, presenting the establishment of rainfall and streamflow gauging stations in an experimental basin states that there is little or no information on the reliability and the quantity of stream flow in many of the mountain streams that abound the central hills. Rainfall 1. Ampitiyawatta and Guo (2009)55 using monthly data from 1965 to 2004 has identified that there is an approximate decreasing trend of 12% per year in the Kalu Ganaga basin rainfall. 2. Herath and Ratnayake (2004)56 describes an analysis of long-term rainfall trends covering the Kotmale and Uma Oya basins of Sri Lanka. A 30-year 60 rain gauge data set has been analyzed to identify the trends in annual and seasonal rainfall. Missing data had been filled from neighboring stations using a correlation and inverse distance algorithm. There has been a decrease in the annual rainfall in the region, while different seasons has shown mixed results. The March–April 1st inter-monsoon period shows the highest decrease where almost all gauges have recorded decreasing rainfall. The paper indicates that in addition to the decreasing rainfall trend, number of rainy days have reduced giving rise to an increasing rain intensity trend. A universal multifractal analysis has been used to compute the changes to rain intensity-frequency relation and results show that there is a decrease of inter-monsoon rainfall, while the intensities and return period of extreme events appear to become shorter. The paper states that these changes could be associated with regional climate changes, and are consistent with projections related to Asia Brown Cloud phenomena 3. Jayawardene, Sonnadara, and Jayewardene (2005)57 utilizing over 100 years of monthly rainfall records between 1869-1998 belonging to 15 meteorology stations of Sri Lanka had reported that no coherent increase or decrease of rainfall in any group of stations had been observed and accordingly the possibility of large scale change over the past century had been ruled out. Records of 1949 onwards had indicated decreasing trends in 13 of the 15 stations reflecting apparent traces of temporal change. 4. A study by Kumara, De Silva and Punyawardene (2004)58 in Kotmale and Kelani catchments has carried out a trend analysis of rainfall data from 1964 – 2001 divided in to two halves. Results had been analysed on a seasonal perspective and it has been indicated that in Kelani catchment, all four stations show negative rainfall trends during First and
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second inter monsoons and three stations show a negative trend in the north east monsoon. During southwest monsoon all four stations have shown a positive trend. In the upper Kotmale catchment, all five rainfall stations have shown decreasing trends during first and second inter monsoons and the North East monsoon where as in the South West monsoon three stations show increasing trends with other two decreasing trend. 5. Maduma Bandara and Wickramagamage (2004)59 in their work had used pentad rainfall data wherever possible along with monthly data for the study period between 1889 and 2002. A study of annual total, seasonal, and inter-monsoonal rainfall, rainy days, wet days and annual temperature trends had indicated an increasing trend in annual temperature, and that rainfall is on the decline with the greatest had been during the South West monsoon and on the western slopes. Study has also made an attempt to conduct and impact analysis through landuse studies which had not produced conclusive results. Authors had indicated long term data availability and cost of data as limitations. 6. Partheepan, Jeyakumar and Manobavan (2005)60 had used monthly rainfall and temperature data of Batticaloa from 1900-2003 to forecast monthly rainfall and temperature and to explore the trend and pattern of seasonal rainfalls. Authors had performed homogeneity and statistical tests prior to carrying out ARIMA model analysis which has indicated that the forecasted annual rainfall behaves in a 10 year cyclic pattern, there is an increasing trend up to the year 2010, maximum mean annual temperature would increase by nearly one degree after next seven years, that the mean annual temperature would not change considerably, and that there is no correlation between mximum annual temperature and annual rainfall. 7. Wijesuriya, Sepalika and Amarasekera (2005)61 A study of dry spells in the rubber growing areas of Sri Lanka selecting 13 regions based on agro-ecological maps. Daily rainfall data of 14 stations from meteorological department, natural resource management center and from the data collected by the rubber research center had been used. Time period covered had been from 1941-2000. The probability of receiving less than or equal to 10mm in different standard weeks of different locations had been high during the period 1971-2000 when compared to the period 1941-1970 indicating an increase in risks of receiving dry spells. 8. Yahiya et al (2009)62 describes a historical relationship of ENSO to Sri Lankan rainfall using monthly date of 16 observatories of Department of Meteorology for the period from 1869 to 1998. Basic statistics for rainfall are provided on a seasonal and regional basis while ranked rainfall anomalies are also presented. Ranking both the seasonal Sri Lankan rainfall and its contemporaneous ENSO index shows a modest by significant association in the January to March, May, July to August and October to December periods. The relationship between the rainfall and ENSO during October to December, January to March and July to August aer statistically significant and it is stated that this association can be used to predict rainfall 3-6 months in advance based on the availability of ENSO predictions. 9. Manchanayaka, Sumanaweera and Jayaratna (1985)63 has commenced the Sri Lankan studies on the identification of loss rates for seven catchments and the results are presented. It has been indicated that a detailed analysis on more floods should be carried out for the identification of a basis for selection of design loss rates for ungauged catchments. The study has reported the loss rates for each storm at each catchment using
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Horton method and Average Storm Method for calculations. The loss rates show a mix of results sometimes showing a wide variation of values from the two methods. 10. Fernando and Wickramasuriya (2004)64 had considered daily rainfall data of Anuradhapura and Ratnapura within the period from 1889 to 2000 to investigate the methods of estimating the Probable Maximum Precipitation(PMP) and strongly suggested that the statistical method of estimating is an efficient and promising area of study in the context of Sri Lanka. Based on the statistical estimates the PMP at Anuradhapura and Ratnapura are 625 mm and 1120 mm respectively. It has been indicated that comparing the statistical and hydro meteorological methods and exploring the suitability of frequency factors within the local climate as a potential research area. Water quality 1. Amarathunga and Sureshkumar (2009)65 in their work has assessed the pollution status and the contribution of land based pollutants from catchments. Monthly variations in the water quality of 12 sampling locations had been analysed for some physio-chemical and biological parameters. Water flow rates have also been measured. The work presents some results and indicates that an average nutrient quantity of 122 lb/day gets transported to the lagoon through Lenagala Ela. 2. In this work Shariff and co workers (2004)66, the results of regular studies conducted in Kandy Lake for its limnology and water quality including pollution indicative parameterssince mid 1996 and recent studies examining the quality of inflows were compared with the previously published works. Areal photographs and topo sheets for comparison of land use, demographic data from the department of Census and Statistics, Fish population data from National Aquatic Resources Agency and a preliminary survey of temporary visitors conduced specifically for the study were the other inputs. Annual limnological characteristics are shown in the paper along with wastewater inflows, land use and population. Although discontinuous fluctuations occur in the tropic attributes in Kandy lake, its self recovery has been mentioned as Uncertain because of increasing urban pressure and non-harvesting nature. 3. A water quality study67 (Silva 2003) of 20 dry zone irrigation reservoirs considering electrical conductivity, total alkalinity, pH, major cations and anions reveals that status and trends in quality of irrigation water are within the ranges stipulated by international agencies. However, reservoirs located extreme downstream of the dry zone rivers are vulnerable for quality changes due to high evaporation and routine irrigations & drainage practices. From the available long term data on electrical conductivity the Silva (2003) concludes that in Parakrama Samudra and Minneriya that has been no significant increase in total dissolved salts and that the available amounts are well below the threshold value. 4. Silva (1996)68 in his review work has considered Kelani River and estuary, Negombo Lagoon, Bolgoda Lake, Koggala Lagoon, Kotmale reservoir, Kala wewa and Rajangana Tank, Kandy Lake and Meda Ela, Hamilton canal, and Hikkaduwa Marine sanctuary in an attempt to compile the available information because it had been noted that Sri Lanka has ignored the importance of acquisition, documentation, and dissemination of information related to water quality. The study is categorized as an attempt to identify the status of water quality and trends in pollution. In the conclusion, it is stated that studies have attempted to identify salinity intrusion in Kelani River, Faecal contamination in
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Kelani Estuary, micro nutrients in Kotmale reservoir, silt loading and sedimentation of Negombo Lagoon etc., among several other factors. This work indicates that available data on water quality cannot be used as baseline information even in the case of impact assessment exercises mainly due to inconsistency and widely differing methodologies employed. The common recommendation had been to ensure the availability of a scientific monitoring program and surveys with quality assurance checks and balances. Parameter identification, number of sampling sites, frequency of testing, use of proper methods sampling and analysis including use of mathematical models require improvement in approach. 5. Gunawardena et al (2009)69 in a study of water quality of 9 locations at Bolgoda Lake had observed 12 water quality parameters determined according to standard test methods published by American Public Health Association. Monthly sampling had been carried out from September 2008 to May 2009 representing wet and dry seasons in the year. It has been indicated that these data are part of a preliminary study carried out on ambient water quality of Bolgoda Lake and are intended to serve as baseline data to monitor any further pollution due to anthropogenic activities. 6. Matsuno, Elkaduwa and Shinogi (1998)70 presents a study on water quality of reservoirs in the Lunugamwehera and Ellegala Irrigation System from January to Decempber 1997 based on field work carried out on a monthly basis. Water samples from all major reservoirs have been collected and analysed for the contents of Ca, Mg, and Na, while measurements of Electrical Conductivity and pH also had been recorded. Information on rainfall, reservoir inflow and outflow, tank water levels, irrigation water issues etc., have been obtained from the Irrigation Department. Study has reported summary statistics of temperature, pH, EC and Sodium Absorption Ratio levels of irrigation water in the Kirindi Oya Project. Among other conclusions the paper indicates that a higher level of EC was observed in drainage water when compared with the reservoir water and that a lower standard deviation of reservoir EC indicated a relatively stable EC relating to seasons and locations. 7. Priadarshana and Sandaruwan (2004)71 have investigated a comparison of water quality and phytoplankton in the Rekawa lagoon prior to construction of the causeway, after construction of a causeway and after construction of a bridge. Water quality and Phytoplankton data had been collected for a period of fifteen months from 1994 december to 1995 March and again from 2004 May to October. Data from a previous literature in 1988 had also been used. The localization of water quality had shown an improvement after modification of causeway to a Bridge by increasing waterway by approximately 30%. However the mean salinity of the lagoon had not recovered and Phytoplankton species had shown a similar localization during the period of 1984 to 2000. The research indicates to the necessity of water quality evaluations when keeping surface water drainage openings. 8. Weerasekera et al (2009)72 has monitored the monthly variations in physico-chemical parameters in Uma Oya and Badulu Oya sub catchments of Mahaweli River using test samples from 13 locations and within the period from April to October 2007. Results had revealed that the sampling locations from two catchments except four locations were within the Sri Lanka limit for fish and aquatic life.
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9. Dayawansa (2005)73 has indicated the application potential of a Minimum Information requirement model to Uma Oya catchment and a small agriculture dominated sub catchment called Sandatenna. The work which has used a 14 calibration parameter model named TOPCAT-N based on a simple statistical representation, had stated the capability of model to closely simulate observed flow pattern and the capability of representing the transport, dilution, localized events, etc. Author mentions the need to address issues of data scarcities and data errors, need for having simple, user friendly and sufficiently comprehensive with multiple capability models, potential of calibration with available data and the adequate presentation of agriculture and hydrology in the model outputs. 10. Weerakoon (2002)74 reports a case study containing the identification and quantification of the spatially varied wastewater discharges and accompanied pollutant loads along the Kandy Mid Canal which is a 4 km long urban canal having a width between 10-15 m and a catchment area of approximately 13 square km. The author had incorporated a one dimensional water quality model to predict total Nitrogen, Bio Chemical Oxygen Demand and Dissolve Oxygen concentrations. The spreadsheet model had been developed with data through a project specific field survey of infrastructure and tested with reported field measurements during previous similar work. The author indicates a graphical match of model outputs and observations and describes the application of results to identified application cases. Storage systems 1. Nandalal (1998)75 present s a study of inflows to the Moragahakanda reservoir using a monthly simulation model with an objective function minimizing the expected value of the annual sum of squared shortages of supply water. Study period data from 1950-1977 has been obtained from a JICA (Japan International Cooperation Agency) feasibility report and Water Management Secretariat of the Mahaweli Authority. The study reports the capability and advantages of modelling to derive and assess long term operation of a complex reservoir system. The model indicates the need to apply a suitable reliability criteria for optimization. As the model outputs the paper has presented an evaluation of alternatives identified at the feasibility stage. 2. Nandalal (2002)76 has compared the application of stochastic dynamic programming method with the application of generic algorithms using the Samanalawewa and Udawalawe reservoir systems as case study. The system has been simulated with developed operation rules for a period of 6 years for which actual operation pattern was available. The model to derive operation policies for the two reservoirs was based on a 37 year long record of monthly streamflow data from 1950-1986. The irrigation demands were those prepared for the feasibility study of Walawe Irrigation Upgrading and Extension Project of 1992. The comparison of the performance has indicated that operation rules from the two methods were better than the actual operation, and that the bet performance was from Generic Algorithm based rules 3. Meegassagama tank is in the Thirappane Tank Cascade System was studied by De Silva (2003)77 and leads to a monthly water balance for the typical year of 1997 and 1998 which has identified that more than 50% of the water leaves the tank as seepage losses. 4. Jayatilaka et al (2003)78 presents a daily water balance model applied to an irrigation tank cascade system in Anuradhapura, Sri Lanka which employs a modified runoff coefficient
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method and a modified Antecedent Precipitation Index to simply the representation of the non linear runoff generation process. Field data of the tanks in the cascade over a period of 21 months between 1997 July – 1999 April had been used for model calibration and it has been indicated that no model validation had been performed. Results for the data over the calibration period, has shown that tank seepage loss accounted up to 84% of the total inflow to the tank, in comparison with the total water release for irrigation, which was only up to 22% of total inflow. 5. Wijesekera (2001)79 in this work describes a monthly water balance model developed to assess the performance of the Lunugamwehera reservoir water. While reporting the reservoir performance under various scenario of parameter values, the paper recommends the seepage coefficient study using soil moisture parameter measurements for better estimates and identify pan evaporation values from the reservoir to provide better controlled water management. 6. Wijeyesekera (1977)80 in this work has carried out a reservoir operation study on the Kalatuwawa by applying a crical operation method to obtain an optimum performance of the reservoir by ensuring that the storage level does not fall below the critical storage curve unless two mosoons have failed. The study indicates that non availability of inflow data as a major limitation. Though a hydrologic analysis for the reservoir between 1968 and 1973 had been carried out for the study, it has been indicated that for reliability, hydrologic data collection and analysis should be continued to estimate precipitation changes, sedimentation and evaporation. Water policy and strategy 1. Thrimahavithana (2006)81 indicates a field survey conducted in Nilwala River Basin though not presented in the paper. A conceptual outline on the need of a Sri Lankan water institution has been written with discussion of sub basin level functions and water user associations. 2. In the paper on water allocation among different water use sectors, Aheeyar, Nanayakkara and Bandara(2010)82 discusses a seriousness of a limitation as a result of the absence of an institutional arrangement for conflict resolution and the need for an apex body for inter-sectoral coordination by mentioning issues pertaining to Kalthota Irrigation Scheme and the Kirindi oya irrigation and settlement project 3. In this work Muthukuda (1998)83 has discussed an evaluation of the two projects launched by the government of Sri Lanka. Initial work on the introduction of comprehensive water resources management was done in 1988 and then stemming from that a project funded by the Asian Development Bank was conducted between 1995 and 1996. The study lists the major factors identified during the research as, lack of ownership, absence of mechanism for internalization of policy implementation, absence of pilot testing phase, lack of investments for activities proposed for policy implementations, inadequacy of prior agreements of taking over of tasks, and the deficiencies in the targeted time frame and funding specifics. The research recommends a strong professional approach for establishing policy, institutions etc., for water resources management.
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4. Nanayakkara (2010)84 in his paper presents selected key themes and issues which may help to stimulate the formulation and adoption of an improved water resource policy statement and argues that what is important in the case of water is not the question of ‘ownership’ but regulating the user rights of water which is a common property resource. The objectives of the paper are to clarify the meaning of the terms ‘ownership’, ‘user rights’, ‘common property rights’, and ‘right to water’; then to analyze and suggest refinements to several water policy themes and issues such as ‘bulk water entitlements’, ‘groundwater management’ and ‘user conflicts’; to outline the roles of institutions for clarity in implementation. 5. Ratnayaka (2004)85 in his work makes a review of how the governance of water in Sri Lanka had been carried out and culminates the documentation with a discussion of a vision. This publication includes a discussion of water policy in Sri Lanka dating back to the Second World War and indicates that the policies and strategies in natural resources have been mostly driven by political or project demands, resulting in institutional arrangements and legal backstopping based on project covenants rather than carefully thought out strategies or action plans. This work which presents a good review of the institutional arrangements, water rights, stakeholder involvement, cost sharing, demand management etc., indicates the expectations that in future there will be good facilitation of the integration of sectoral demands, adequate provision for transparency of transactions, and better regulation and monitoring of water sector activities and promotion of integrated water resources management. 6. Atapattu (2004)86 in his work has presented rationale and basis for valuing water citing from literature and example cases from the irrigated agriculture sector and the National Water Supply and Drainage Board of Sri Lanka. The paper while discussing whether water should be a public good or an economic good raises the issues of pricing of water, quantifying and computing value of water, valuing multiple uses of water such as water for agriculture and municipal supplies. This discussion paper briefly mentions about virtual water, and experiences of water pricing in other countries. Highlights the factor that water governance in Sri Lanka is dominated by state organizations and points to the limiting influence other stakeholders have in the use and management of the resource. This paper points to problem areas that could be investigated through planned research projects. 7. Dilhani and Gunawardena (2006)87 conducted a stratified sample survey in the Lunugamwehera major irrigation scheme and Padawwewa minor irrigation scheme in Hambantota district to identify training needs assessments in integrated water resources management using a total of 100 farmers in two batches. It has been identified that it is premature to train farmers in difficult concepts such as IWRM Climate change 1. Basnayaka and Vithanage (2004)88 - Sri Lankan rainfall is predicted under the scenarios proposed by the IPCC. Results for the Baseline period 1961-1990 are presented along with a comparison of applicability of down scaling methods. 2. Chandimala and Zubair (2004)89 reports of a rainfall study for the period between 19252000 together with a study of streamflow or ranfall relationship with ENSO indices. Catchment rainfall correlates moderately with ENSO on a monthly basis. Paper describes
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the clear evidence of ENSO based predictability for the Kelani Streamflow. The paper suggests that the Streamflow can be predicted with modest but useful skill based on ENSO indices for January to September or separately for April to September and October to December. 3. Jayathilleke et al (2005)90 in this work provides detailed account of the spatial variation of air temperature in Sri Lanka, Temperature trends, district wise distribution of annual rainfall and equivalent water volumes, rainfall in seasons and the spatial distribution of rainfall seasons, climate change scenario for management of water resource, district wise climate model predicted rainfall, climate change effect on components such as soil moisture, floods, droughts and water quality. Among overall data presented in the work, it is stated that there is a significant change in the rainfall from 1970 where average annual rainfall has been below average right through upto 2000 except for three years. This paper goes on to indicate that the change in rainfall would cause a shifting of demarcation lines of current rainfall zoning, with parts of earlier wet zone getting into the intermediate zone and parts from the earlier intermediate zone falling into the Dry Zone. Districts of Matale, Kandy, Badulla, NuwaraEliya are said to indicate a substantial decrease in rainfall indicating substantial issues for surface water in the downstream. The paper indicates the importance of using coupled climate-hydrology models to forecast Streamflow and points out that only a few studies have been performed in this direction. 4. Kiem , Hapuarachchi and Takeuchi (2004)91 reports a study where historical monthly precipitation records pertaining to 15 stations of Sri Lanka from 1871 -1980 are analyzed to determine 1) the magnitude of ENSO impacts and 2) how ENSO impacts vary due to the Indian Ocean Dipole and multi-decadal climate variability. The study has demonstrated the impacts of multi-temporal climate variability on Maha rainfall, and a significant influence of multi-decadal climate variability with multi-year periods of abnormal rainfall conditions being evident in Sri Lanka’s historical records. The study stresses the need to establish the climate variability insights and the need to test the hydrologic models to ensure that the simulated outputs reproduce the natural variability evident in the observed records. The paper based on its findings mentions that it may be misleading to use the 1961to1980 period as the climatological normal to infer trends or to make water resources management decisions and stresses the need to make appropriate verifications for relevant studies. 5. Nandalal, Rathnayaka and Sachindra (2009)92 carriedout a precipitation prediction of Nilwala Ganga Basin using two day data sets for 9/12/2008 and 19/302009 using various micro physics schemes in Weather Research and Forecasting Model. Observed rainfalls from 6 gauging stations on a 5kmx5km grid were used for checking accuray. Ferrier Scheme has been found to produce the best prediction for both datasets. 6. Pathirana and Herath (2004)93 reports of a atmospheric forcing scenario development an investigation to understand and predict the atmospheric forcing effects of aerosol-driven climatic change on the local hydrological scale. The work has carried out a regression analysis for a one year period at 4 km resolution with different levels of model nesting considering a spatial extent of 33x36 pixels and using daily observations between 2002 and 2003. Report indicates a constraint of huge computational costs which had restricted the study simulations. Works indicates that there is a clear indication of rainfall reduction and that the percentage reduction is larger for small intensities.
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7. Zubair et al (2004a)94 indicates an attempt to downscale the 250km, GCM model rainfall predictions to a 20 km grid for Sri Lanka. This work using GCM wind fields as the average of 24 forecasts made for each season and circulation fields between 1950-1980 with observations on ground, leads to an enhancement of cross validated correlation skill scores for GCM predicted rainfall and for downscaled predictions over the island. The work indicates the need to carryout further work especially to consider how best to represent uncertainty in the seasonal forecasts. 8. Wijesekera (2010)95 had carried out spatially distributed irrigation water demand modelling to assess the administrative district wise requirements in the year 2025. Reservoir water balance modelling had been carried out for four districts namely Anuradhapura, Ampara, Pollonnaruwa and Kurunegala, to study the adequacy of minor irrigation reservoirs for storage of surface water resources. Present work describes the modelling efforts that incorporated system deterioration due lack of maintenance superimposed on the climate changes. The study used irrigation department guidelines, published data and made rational assumptions to quantify the impacts on the irrigation systems. Published data included long term rainfall and climate data analysis results with results from a district based water balance study for 1991. It was revealed that it is necessary to carryout detailed studies on individual reservoir systems based on the alarms raised by the study 9. A simple water balance method with GIS has been used to model and map the change in rainfall and soil moisture deficits under Climate change scenario pertaining to UK Hadley Centre for Climate Prediction and Research model (HadCM3) and selected IPCC SRES scenarios (A2 and B2) for the 2050s using Anuradhapura with 1988-1997 daily climatic data a the study area along with baseline climatology dataset of International Water Management Institute having approximate resolution of 16kmx16km96. Predicted average increases in maximum Potential Soil Moisture Deficit above the base line are in order of 8%-53% for 2050s based on A2 scenario over the dry and intermediate zones. It has been identified that the climate change impacts increase the rainfall in south and south-western regions and decrease it in east and north eastern regions along with a 2.1°C temperature increase in Anuradhapura. 10. Peiris, Samitha and Fernando (2007)97 analyzing variability of sunshine hours and temperature in Badulla, Thalawakele, Ratnapura and Hantana of major tea growing area on an annual basis using data from 1976-2005, have indicated evidence of changes in maximum, minimum and diurnal temperature and also the bright sunshine hours though not consistent across locations. Hence a recommendation has been made to carryout detailed analysis at regional level. 11. Zubair et al (2004b)98 had performed quality checks on 100years of monthly mean, maximum and minimum temperature data of 18 Sri Lankan stations from the meteorological department to carryout a perform climate change estimates. Based on quality checks all data of several stations prior to 1950 had been discarded and in some stations prior to 1920 had been discarded to arrive at a data set filtered by the both the present study and previous recommendations. Analyses trends had shown that for most stations for the period from 1960-2001 there is a modest warming trend for the period from 1960-2001 but larger differences for earlier periods. The warming trend of 2.6oC/100 years for annual average maximum temperatures and 1.7 oC/100 years for annual average minimum temperature from 1961-2000, shown in the study are steeper
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than the globally averaged warming trend of 0.4oC/100 years. The authors indicate a research to identify the applicability of similar analysis to high density and high quality rainfall data. 12. The change of eco-climatic zones of Sri Lanka as a result of climate change outputs as predicted with the GFDL and CCCM scenario using mean monthly climatic data from 1960-190 from 21 stations and interpolated to 0.125° x 0.125° grids99 has presented results indicating decreases in the wet zone and increases in both the Dry and Intermediate Zones though at different magnitudes. Both scenarios have indicated a potential northward shift of intermediate zone forests. Summary statistics Outline It is necessary to state that the review attempted to cover as many papers that could be accessed either online or through journal publications of which full paper could be obtained by the author. Abstracts have been included only in the case of published volumes of the Proceedings of Annual Sessions of the Sri Lanka Association for Advancement of Science. Present work reviewed 91 publications related to surface water resources of Sri Lanka. Though the list of references in these works indicated more work on Surface water of Sri Lanka, full publications were not accessible due to various reasons such as, difficulty in contacting the source, absence of copies at known libraries or over the internet, copyright issues of the publisher etc. The papers which were available and felt as relevant have been reviewed. In the present work a review of consultancy reports which had not explicitly indicated as research efforts were not considered. Referencing to works carried out by a consultancy in most of the reports, provide extremely limited opportunity for an independent verification of computational methods or the techniques used, so that the validity of the quoted results could be ascertained. Most consultancy reports due to lack of evidence to indicate that the work had undergone and independent review, showed to possess limited value for the enhancement of scientific knowledge or to contribute towards making critical management decisions under limiting conditions. Since consultancies are expert services provided in a specific area of work, most consultancies carry value added works other than those extracted from already available work. In certain cases consultancy reports contain numerical figures such as those pertaining to surface water use, surface water allocations, coefficients for surface water estimation which are sought after by water managers and researchers. Therefore it is important that consultancy efforts are converted to reviewed documents that could be used with confidence by the research community. The references 100,101,102 and 103 in the list are examples of consultancy reports submitted to various organizations in order to fulfill project specific terms of references and not specifically labeled as research efforts. All these reports carry valuable information mostly extracted from other sources. However none of the reports carry a clear indication of the value additions done by each consultancy. Sri Lanka National Water Development Report104 is a special report providing details of the country to the World Water Assessment Report of the United Nations. This report contains details and summaries of water resources of Sri Lanka in which the editors had linked the documentation to the proceedings of a preparatory workshop and several specific case studies105 This report provides links to the referenced material but does not explicitly
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indicate the value additions by authors of specific works which had contributed to knowledge about the national surface water resources. The present review has not included this report too. Publication theme Among the reviewed papers there were 21 on water resources, 6 on surface water, 12 on floods, 7 on streamflow, 10 on rainfall, 10 on water quality, 6 on storage systems, 7 on water policy and strategy, and 12 on climate change. The papers were also grouped in to sub sections. In this effort most papers had multiple objectives and in some cases it was necessary to fit a paper to the closest category due to the limitation of information given in the paper and the classification used in the review. Though it may have been good to describe a single paper in several subsectors as appropriate, the present review felt that it is better to classify a given paper only once in a selected subsection classification hoping this method would assess the situation of the country in a representative manner. The summaries of research in different sub sections as indicated previously are in Table 1. In case of sub groups, rainfall studies as a section on its own and jointly in relation to the climate change is the highest area of interest having a total of 15 reviews. The next are water resources modelling(9), water resources (7), streamflow estimations in gauged catchments (5) and four each in surface water evaporation, recurrence intervals and flood frequency, surface water quality, surface water quality measurement. It could be noted that in most of the other area, either no work had been reported in the papers reviewed, or had 1,2 or 3 papers in each section. Temporal and spatial variations The review also looked at the temporal resolution of the data used for each study and it was found that 23 publications were based on daily data, 25 were based on monthly data, and 36 had not either mentioned the time resolution or time interval was not relevant for the reported work. One modelling work based on 15 minute interval data and another event based publication were the only two studies in the less than daily time scale. The availability of monthly rainfall and temperature data was indicated by several studies which used over 100 year of data. Only one temperature study could be identified using a daily dataset as lengthier as 30 years. Rainfall studies using hourly data were not within the reviewed set of publications. Daily rainfall studies were using very short duration datasets except for two studies which used over 60 years of data but had restricted the study to maximum of two locations. Other research such as water resources, reservoir operation, water quality etc., had used varying monthly datasets spanning from 1-80 years. In general and on average, datasets that had been used for streamflow modelling, annual peak, drought, regression analysis etc., varied from 7-30 years. Streamflow modelling had used datasets of approximately 7-10 years whereas there was a single ungauged catchment modelling and a single peak flow analysis conducted using a dataset in the range of 30 years. With respect to the spatial extent of the considered research, there were 28 publications which had reported work on basins and out of which 22 were on small basins. There were nines studies done for reservoirs and out of that seven had been for small reservoirs. 4
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number of works were on districts, 4 on irrigation scheme level, 1 for the dry zone and 1 for the wet zone, two for small spatial extents and the others had not indicated a spatial extent on which their works could be related. With respect to spatial locations, there were 16 works in the context of Sri Lanka as a whole, studies in the wet zone numbered 44 with another 19 falling into the category of dry zone studies. Other studies either was a mix of details or were without indicating a location for grouping. The basins also showed popularity inclination with river Mahaweli in the lead (13), Walawe (10), Kelani (8), Kalu and Niwala (5 each), Deduru Oya and Gin Ganga (2 each), Bolgoda (1) and Menik (1). The others could not be grouped due to inadequate details or due to the grouping restrictions. Discussion 1. Common Review summaries presented in this work extracted key information from each publication in order to obtain a scientific judgment on the research that had been executed. These summaries indicate the lack of presenting key information in most of the publications. Some have not indicated a specific study area, data durations, methods of computations, method used for verification etc., and these deficiencies make a publication appear less useful. This could be either due to a weakness of the research itself or due to an unnoticed omission and steps should be taken to improve this situation. Most publications did not indicate the quality of research output except the inclusion of qualitative statements such as claims of “sufficient accuracy”, “good matching” etc., which indicated the need for more work in the same area to ascertain a scientific direction to proceed to the next stage. Reviewed literature indicated the need of encouraging the use of numerical indicators along with visual observations for reporting research outputs. Use of terminology when reporting model calibration and verification was not consistent probably indicating a lack of understanding on this particular subject area. Reporting inconsistencies require careful filtering of results presented in the publications for any useful comparisons. Some research had used the entire data set for calibration while some appeared to have used a too short duration. Data periods selected for calibration and verification warranted the inclusion of either sufficient literature references reinforcing the selection or an explicit indication reflecting that the selected data periods contain desired qualities for model excitations. It is noted that if incorporation of such supportive documentation could be fostered then results presented in respective publications could be confidently used for scientific work. A lack of describing data collection methods in most publications could be noted in the review and this undervalues the reported outputs. Most research in their documentation had not indicated data sources, while quite a few publications had not made even a passing remark as to whether the data used had undergone a quality check. One paper had been critical about the strength of water quality testing and hence the value of reported outputs. These observations may lead a reader to conclude as having already quality checked base data with the collecting agencies and easily available for users. Even if it is so, at least research-specific data collection programs should be encouraged to mention their quality checking process for user benefit. There may be another reason for not providing details of data and it could be due to data accessibility problems. In case the data are beyond the resource limitations then a researcher may have used a previously obtained dataset or a web
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source to fulfill his or her desire and enthusiasm for research and then reported the results. This factor must also be taken into consideration when encouraging authors to report data sources especially in the light of national benefits achieved when promoting surface water research. Methods used for selection of models and methods, or the determination of a particular direction for analysis was lacking in many publications reviewed. This causes two concerns, the straightforward one is the loss of confidence when attempting to use the published results and the other is the loss of an opportunity for science to build on the other research methods and directions that had been already performed and reported in the same area of work. A similar statement could be made on the ways of reporting research results. It is important that the publications make every attempt to show the methods that had been used to confirm the validity or to assess the degree of validity of presented results. A notable issue was either the lack of conclusions, lack of quoting conclusive outputs that had risen from the presented research, or the need to stretch the authors to extend the reported hard work a bit further to converge as conclusions. These factors should be carefully integrated in to surface water research programs to ensure good quality outputs. 2. Thematic sections Out of the sub sections identified and listed in Table 1, only 58% had been investigated or addressed even once. Not only the areas that appear to remain untouched but also the sections with inadequate research efforts should be subjected to concentrated and focused evaluations and supported with research activity initiations. The review could not identify any research directly on surface water resources, such as assessment of surface water resources pertaining to a particular spatial entity and at a particular temporal resolution. However, most publications that were reviewed led to either quantifying a part of surface water resources or identifying characteristics of a component. Though there were several research works and reports providing values contributing to evaluation of surface water resources, such documentations do not either indicate supporting work leading to scientific research or evidence of research on presented values. Review did not find any studies on rainfall-runoff ratios relating to watershed land cover; there were very limited studies relevant to catchment yields; and there was one study on loss rates. Therefore focused research in such areas is necessary in order to strengthen the identification of rainfall contribution to surface runoff along with its spatial variation at a scale meaningful for Sri Lankan applications. Limited seepage coefficient studies that could be identified in the review indicated a significant deviation of values from those used in the Irrigation Department Guidelines. This causes problems for those who carryout surface water quantifications for project evaluations because both, the values in guidelines and values in reported cases do not appear sufficient to make a judgment regarding practical use. Mathematical modelling of surface runoff, water resources modelling, flood estimations etc., indicated use of several models for prediction of surface water flow in streams and flood runoff hydrographs. Such limited numbers of modelling efforts in literature only present the readers with test case studies which mostly demonstrate the suitability of a model, its application potential, and possibility to use a particular dataset at a selected spatial entity. Due to lack of adequate work in controlled environments it is difficult for a practitioner to assess which model or models would satisfactorily lead to the estimation of Sri Lanka’s surface water resources within a desired level of accuracy.
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Table 1: Number of Review Papers in Each Main and Sub Section
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Classification 1. Water resources 1. Water resources 2. Water resources modelling 3. Catchment yield 4. Droughts 5. Low flow studies 2. Surface water 1. Surface water assessments in watersheds 2. Surface runoff coefficients 3. Surface water infiltration and seepage 4. Surface water evaporation 5. Surface flow rating curves 6. Surface water extractions 7. Surface water conservation 8. Surface water development potential estimation 9. Surface water economics 10. Surface water 11. Wetlands 3. Floods 1. Flood estimation in gauged catchments 2. Flood estimation in ungauged catchments 3. Flood modelling 4. Recurrence Intervals and flood frequency 5. Surface water drainage 6. Drainage canal network 4. Streamflow 1. Streamflow estimation in ungauged catchments 2. Streamflow estimation in gauged catchments 3. Flow measurement 4. Flow measurement network 5. River network identification, assessment, development, 6. Environmental Flows 5. Rainfall 1. Trends
2. Loss rates 3. Probable Maximum Precipitation 6. Water quality 1. Surface water quality, 2. Water quality measurement 3. Water quality measurement network research 4. Water quality modelling 7. Storage systems 1. Small and medium tank systems 2. Reservoir storage 3. Seepage 4. Releases 5. Reservoir operation 6. Reservoir mapping 7. Networking 8. Monitoring, 9. Reservoir assessments 8. Water policy and strategy 1. Multiple use of surface water, 2. Water user association and 3. Water institutes 4. Water policy 5. Water pricing 6. Training and human resource development 9. Climate change 1. Rainfall 2. Evaporation, 3. Water use 4. Surface water storage 5. Irrigation 6. Hydropower 7. Drinking water 8. Wetlands 9. Water quality 10. Floods and drainage 11. Environmental flows 12. Soil Moisture 13. Temperature 14. Forest cover
No 21 7 9 2 1 2 6 1
4
1 12 1 2 3 4 1 1 7 1 5
1
1 1 10 4 4
2 6 2
1 3
7
1 4 1 1 12 7
1
1 2 1
10 8
This review noted hints that indicated published work having a bias towards study locations probably due to availability of data, ease of modelling, ease of access for site visits or due to the interest of a project of national importance. Among the publications this review noted one abstract describing the comparison of a lumped and a distributed model in an upper watershed as the only work towards distributed basin scale modelling. The importance of such studies increases with the increasing demand for the knowledge on surface resources that arise either as a result of the efforts to harness what is available, or when making suitable 86
interventions through the incorporation of physical changes within a watershed. Observed low modelling efforts may be either due to lack of data, non availability of modelling tools, lack of expertise or lack of encouragement from those who manage the surface water resources on behalf of the public. It was noteworthy that GIS based hydrologic research, Hydraulic Modelling, one and two dimensional catchment modelling are at a very basic level both in terms of use of models and application case studies. In case of water quality, 80% of research work published were either reporting the status, or measurements. Only two cases could be noted to attempt modelling of water quality. This area of surface water research appears to require moving from measurements to modelling of systems through systematic and continuous quality measurements of the resource for validating the predictions. This would enable better assessment and management of surface water resources. Though Sri Lanka has a quite a number of cascade reservoir systems which are mostly located in the dry zone, the review noted the absence of research on reservoir assessments, reservoir storage, reservoir releases etc. A notable factor was that the reservoir studies reviewed were carried out on a monthly temporal resolution. It is felt that though this temporal resolution would point to the issues concerning the surface water storage systems, it would not be adequate for scientific knowledge enhancements, judgments or evaluations.Research on measurement networks, methods and measurements pertaining to surface water storage would require strengthening. It was noted that one reviewed paper which contained the assessment of climate change effects on irrigation, had pointed to the importance of making a review of Sri Lanka’s reservoir storage systems in the light of changing evaporation and rainfall. Water policy publications pointed to the gross inadequacy of quantitative research in this area. Documentation indicated the possibility that studies had not grown to specifically address various components of water resources and hence could not identify outputs that separately addressed surface water resources. Published works on water policy indicated a strong desire for developing a better water policy for the nation and were based on various concepts which pointed to the need of founding such concepts on reasonable scientific data. It was felt that the review works which were in those publications provide a suitable background to initiate a well thought out research programme because surface water resource limitations are already beginning to surface. Majority of rainfall and climate data were using monthly datasets. The availability of long duration data sets could be noted from the research but the quality of data appears to be a concern which had been raised in many publications. Almost all reviewed research works on rainfall and climate indicated trend analysis and predictions arising from such regressions. However, validation of rainfall and climate models using historical records and downscaling of climate model outputs were shown as important requirements. Identification of spatial distribution of rainfall at basin scale using the available data had been carried out to discuss the seasonal variability and it may be necessary to expand such works to finer spatial resolutions which would in turn support distributed surface water modelling. 3. Management 87
In general, the review indicates that there are some areas such as streamflow and rainfall that possess a significant national database but issues such as quality and availability with respect to access, temporal and spatial resolutions have not led to reaping full benefits from research efforts. This points to the fact that there is much scope to harness the benefits of public spending on data collection programs. The review also shows that there is very limited work in most of the specific areas in the subject of surface water resource. This shows a strong need to consolidate the research results that have been carried thus far through a well planned research program for conducting more similar work both on the same datasets and also on different catchments at various spatial scales. Most of the research conclusions explicitly recommend further research to strengthen the presented outputs but it is noted that such continuations which are invaluable for confidence building research are a rarity. Other than the above it is also important for the surface water management agencies to identify signals given by on going research and then lead concentrated efforts for more case studies to arrive at guidelines for practice and design. This reflected as a notable omission as there was no evidence of such research, references, or revision of guidelines over time. Review also indicated the lack of cross referencing of similar works by other researchers even though their work had been performed in the same subject area and for a location in Sri Lanka. This usually reflects an action during early stages of research in a specific area of work but it also could be due to non availability of full publications of other work for reference. However it is extremely important to inculcate the need to build on previous research facilitating adequate literature reviews, critical comparison of methods and results etc., so that more conclusive results could be achieved without spending much time on circuitous routes. At the same time it is important to provide research publication inventories or establish library networks with water research publications so that sharing of published information, consultancy reports and monographs could be done with ease. It is very important for research management personnel to look at the present review in the light of identifying whether there is a government role in surface water research, whether importance of surface water research should be looked at from a point of view of problem solving or advancement of fundamental knowledge, whether the surface water research is fillings the gaps in knowledge, of national significance, progressing and complementing the overall research portfolio106. Conclusions and recommendations •
In Sri Lanka, there is a significant research effort towards the understanding of surface water resources and its various aspects which is associated with a significantly long rainfall, streamflow and reservoir storage datasets.
•
Assessment of research coverage with respect to sub components of surface water resources revealed that the reviewed papers covered only 58% and that some sections had a very weak coverage. There is a strong need to critically evaluate and organize 88
the surface water resources research programs in a systematic manner covering various contributory aspects while adequately considering the national significance of such research efforts along with suitable stakeholder consultations. •
Majority of surface water resources publications required the inclusion of important information for users to capture the importance of the research outputs. Therefore, surface water research should be encouraged while adequately guiding researchers to provide key information of research so that best use of both research outputs and inputs of public funds could be ascertained.
•
Surface water research had mostly used monthly data sets and had demonstrated only very limited modelling efforts using high resolution data. Therefore water data collection agencies should be encouraged to provide data of higher temporal and spatial resolutions for more meaningful research.
•
Reported research works demonstrated applications of methods and data, but did not converge on establishing methods and values for use by surface water resources practitioners with confidence. It is important for water resources management agencies and the state to consolidate the available research outputs through more directed research to serve as guidelines for practical use.
•
There was no evidence of directed research towards important areas of surface water resource assessments and most works were in the era of observation and conceptualization. There is a strong need for research and resource managers to identify thrust areas and conduct directed research to converge on verified outputs.
•
Surface water resources research pertaining to Sri Lanka requires the encouragement of cross referencing of other works. Review pointed that a greater benefit could be achieved by providing at least an inventory of publications pertaining to Sri Lanka’s surface water resources. Accordingly it is important to form a network of libraries facilitating researchers with easy access to literature.
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Proceedings of the
National Forum on Water Research ‘Identification of Gaps and Priorities’
Organized by
National Science Foundation Sponsored by
Dam Safety and Water Resources Planning Project Ministry of Irrigation and Water Resources Management and
UNESCO International Hydrological Programme, New Delhi
Editor
Professor H.D. Gunawardhana
16th and 17th of September 2010 Colombo, Sri Lanka
1
Proceedings of the National Forum on Water Research ‘Identification of Gaps and Priorities’ 16th and 17th September 2010 at Colombo, Sri Lanka.
Copyright :
© National Science Foundation of Sri Lanka
Compiled by
Ms. Amali Ranasinghe with the assistance of the staff of the Research Division of the National Science Foundation
Published by
National Science Foundation 47/5 Vidya Mawatha Colombo -07 Sri Lanka
ISBN : 978-955-590-109-3
2
CONTENTS Title
Page
Technical Session 1 Chairman Rapporteurs
: :
“Water in Society”
Prof. Kapila Goonasekera Prof. K. D. W. Nandalal and Ms. Manjula Amarasinghe
Water for Food, Fibre, Livestock and Aquatic Production
01
Part I - Water for Livestock and Aquatic Production and Food Security D.V.S.de S.Gamage
Water for Food, Fibre, Livestock and Aquatic Production
13
Part II - Irrigated agriculture and water productivity, major and village irrigation, modernization and rehabilitation of systems D.V.S.de S.Gamage Water for Basic Needs and Health Sumitha Sumanaweera and Anura Jayasinghe
23
Water and Environment Niranjanie Ratnayake
46
Technical Session 2 Chairman Rapporteurs
: :
“Water Resources and Disaster Management”
Dr A. M. Mubarak Mr. K.A.U.S. Imbulana
Surface Water Resources and Climate Change N.T.S. Wijesekera
61
Groundwater Resources K.D.W. Nandalal
99
Water Related Disaster Management Part I - Floods, droughts and other disasters, management of disasters and adoption methods P.P. Ghnanapala
118
Water Related Disaster Management Part II - Tends in occurrence of water related disasters K.A.U.S. Imbulana
142
6
Technical Session 3 Chairman Rapporteurs
: :
“Water for Development”
Mr Priyalal Dias Prof. K. D. W. Nandalal and Dr Gowry Moorthy
Water for Industry and Energy Generation
158
Part I - Industry as a water user and water for energy generation Ajith de Alwis
Water for Industry and Energy Generation
167
Part II - Industrial water pollution, prevention and control and hydropower generation potential Rajaratnam Shanthini
Technical Session 4 Chairperson Rapporteur
: :
Caring for Water
Dr Subangi Herath Prof. K. D. W. Nandalal and Dr Inoka Sandanayake
Water, Education and Knowledgebase H.Dasaratha Gunawardhana
185
Water Data and Information System in Sri Lanka N.T.S. Wijesekera
206
Water Governance D. C. H. Senarath
231
7
