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HYDROCLIMATE PROJECTIONS TO ENGINEERING PRACTICES FOR WATER RESOURCES SECTOR ADAPTATION MEASURES Ahmad Jamalluddin S.1, Mohd Zaki M.A.2, Nurul Huda M.A.3, Y.C. Goh3 National Hydraulic Research Institute of Malaysia (NAHRIM) Ministry of Natural Resources and Environment (NRE), MALAYSIA ABSTRACT Malaysia’s water resources sector is currently plagued by three major issues, namely water excess, water shortage, and water pollution. Nine percent of the country lies in flood prone areas. The rainfall occurring between November and January each year constitutes sixty percent of total annual rainfall. The large rainfall amount causes widespread flooding in riverine and coastal areas. Meanwhile, the seasonal distribution and spatial variation of rainfall have resulted in water stress related problems in several regions in the country. Extended periods of drought cause water supply to fall short of water demand in states supporting large scale irrigation for rice cultivation such as Perlis and Kedah. Other industries are not spared either. Heavily industrialized states such as Pulau Pinang, Selangor, and the Federal Territory of Kuala Lumpur face periodic water shortages which are exacerbated by long dry spells. On top of that, rivers and waterways are polluted by urban, industrial and agricultural wastewater. In Klang Valley alone, 60 tons of wastes are dumped into the rivers per day. Behind these issues looms a larger threat – climate change. Climate change and variability together with non-climatic drivers such as population increase, intensive land development, and loss of forests have had physical impacts on the hydrological cycle especially in the recent decades. Increased frequency of floods, increased catchment erosion and siltation, inadequate environmental flows, increased pollution and deterioration of river water quality, and limited water supply are climate change impacts that threaten the sustainability of our water resources. The three major water resources issues – water excess, water shortage, water pollution – together with water governance, which have always been of major concern are expected to worsen with the stimuli of climate change. The impacts can be modeled and projected by means of downscaling approach using the output from Global Circulation Models (GCMs). However, to accommodate and to obtain information of more relevance to water resources and water resources management at watershed scale, higher, fine-resolution (spatial and temporal) and reasonably accurate climate change projection is required. In general, there are two types of climate change downscaling approaches: statistical and dynamic downscaling. Statistical or empirical downscaling rely on current estimates or observations of the spatial distributions of meteorological variables while results from dynamic downscaling method are physically consistent but it is more computationally demanding in terms of both computer time, output storage and cost. Adopting the dynamic downscaling approach, NAHRIM has completed the development of the regional hydrologic-atmospheric model of Peninsular Malaysia, Sabah and Sarawak namely RegHCM-PM (2006) and RegHCM-SS (2010) respectively, as well as Regional Climate Model (RCM) for Peninsular Malaysia, Sabah and Sarawak using PRECIS in 2010. Annual daily mean temperature projection from RegHCM model for the whole Malaysia from year 2020 up to 2099 shows the increase of surface temperature from 0.5°C in the year 1 Director General, NAHRIM Director, Research Centre for Water Resources, NAHRIM 3 Research Officer, Research Centre for Water Resources, NAHRIM 2 2020 to 3.5°C 3 at the e end of the century. The e climate prrojection stud dies for prec cipitation alsso find that more extrem me weather conditions in the future (2025-2050 0) may be exxpected sincce higher maximum m and lower min nimum rainfa all are observed in the projected data. d Figure 1 shows th he map of projected p one day maxim mum precip pitation from RegHCM fo or Peninsula ar Malaysia a. The proje ection also shows incre ease in max ximum mon nthly rainfall of up to 51 5 percent over o Pahang g, Kelantan, and Tereng gganu region ns while the minimum monthly m rainfa all decrease es from 32 to o 61 percentt for the who ole Peninsula ar Malaysia. Figurre 1: Peninsu ular Malaysia a Map of Ma aximum 1 da ay Rainfall The mod del output in terms of pro ojected clima atic parametters such as rainfall, tem mperature an nd evapotranspiration iss very esse ential for the e quantificattion of the potential climate chang ge impacts on o water ressources and d water reso ources mana agement. Th his leads to the necessity for deve eloping engineering me ethodologiess for climate e change a adaptation particularly p t to bridge th he gap betwe een scientific knowledge e and engineering practtices. In othe er words, it is to develo op engineerring knowled dge into practices in wa ater sector, for instance e reviewing of o water syystem manag gement and d plans to a assess the integrity of existing e stru uctures wherre failure co ould result in n loss of life, reviewing d design stand dards for floo od risk mana agement in all a new infrrastructures including water control structures, transp portation strructures an nd electricall, water and waste amenities to incorpo orate climatte change factor, an nd complem menting strucctural appro oaches with h non-structural approa aches such as improve ed rainfall and flood fore ecasting, dissaster warnin ng system and flood hazzard mappin ng as part of a coordinatted disaster prevention and manage ement plan. Above all, a these infformation need to be conveyed to policy ma akers or pla anners to be b implemen nted or enfo orced in the e country. T These are all a part of adaptation a a and mitigatio on measures to cushion n climate cha ange impactt. Adaptation n is primarilyy a local issu ue as it mosttly provides benefits at the local sccale. Adapta ation can havve short-term m effect on the reductio on of vulnerrability. In contrary, c mittigation is a global issue and mostly provide es benefits to t mitigate the t impact of o greenhouse gas by m means of em mission reducction at glob bal scale. Th he frameworks of wate er resourcess management and wa ater servicess evolved from adaptivve managem ment to reduce vulnera ability and e enhance sysstem resilien ncy and rob bustness. Th he framework may ha ave a different combin nation of tools t like ttechnologica al innovation, engineering design change, and multi-objective watershed planning and regulations. Climate change adaptation should be given priority in water sectors as well as in health and coastal sectors where the design, planning and operations of water resources management and water services are required to be adjusted by water related authority. As for an example of the proposed methodology, a case study of Sungai Kedah basin shows that future projected rainfall indicates an increasing trend over the projected years for climate change factor in that area, as shown in Table 1. The climate change factors are incorporated into flood simulation models to project future peak discharge (flood) based on different scenarios. These rainfall projections are used in flood simulation models and the results are subsequently mapped on satellite image (Figure 2) and other information such as total flooded area (Table 2) extracted for further analysis. Table 1: Projected magnitude of peak floods due to climate change impacts in Sungai Kedah Basin. (a) (b) (c) Item Time Horizon Climate Change Factor (CCF) 1 2 3 4 5 2020 2030 2040 2050 2060 1.05 1.09 1.14 1.19 1.25 (a) Baseline (current landuse) (d) 1-Day Design Rainfall (Baseline = 240.6 mm) 245.2 256.5 268.0 280.0 292.6 Peak Discharges (Qp) 100 years ARI (e) (f) (g) Current Future Landuse Adaptation Landuse & & Climate value 3 Climate Change Change (m /s) Scenario Scenario (Baseline Qp= 2047.9m3/s) 2111.2 2313.7 266 2267.9 2438.0 429 2430.2 2613.8 598 2601.9 2799.9 776 2785.3 2997.6 966 (b) 2020 (current landuse) (c) 2060 (current landuse) Figure 2: Generated 100 year ARI Flood Inundation Map of Sungai Kedah Table 2: Flooded area by depth. Flooded area by depth (km2) Landuse Scenarios 0.01 ‐ 0.5 m 0.5 ‐ 1.2 m >1.2 m Total Current Baseline 2020 2030 2040 2050 2060 50.50 50.67 50.65 50.59 49.88 48.44 41.55 42.13 43.67 45.11 47.21 49.02 35.57 36.42 38.56 40.65 43.06 45.16 127.62 129.21 132.88 136.34 140.16 142.62 Future Baseline 2020 2030 2040 2050 2060 51.10 51.24 51.01 50.51 49.13 48.16 43.30 43.91 45.18 46.86 49.17 50.00 37.07 37.92 39.90 42.00 44.20 46.95 131.47 133.06 136.10 139.36 142.50 145.10 In conclusion, this paper encompassed and deliberated water sector related issues and problems, and also discussed methods to bridge the gap between scientific knowledge into engineering knowledge and solution in the context of water and climate change impacts in Malaysia. In addition, it also showed the methodology to mainstream climate change adaptation in water sector in order to cushion and minimise the impacts of climate change and variability and non-climatic forcing. Keywords: Climate change, Global Circulation Model, downscaling, regional hydro-climate model, water resources. Acknowledgement: The Sungai Kedah study described in this paper is funded by Economic Planning Unit (EPU) of the Prime Minister’s Department and the United Nations Development Programme (UNDP).