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LLM - Digital Humanities 16

ERROR: type should be string, got "https://doi.org/10.1051/e3sconf/20199806014 https://doi.org/10.1051/e3sconf/20199806014 E3S Web of Conferences 98, 06014 (2019) \nWRI-16 Climate change impact assessment on \nwater security in South Africa: A case \nstudy in a semi-arid river basin Yali Woyessa1,* 1Department of Civil Engineering, Central University of Technology, Free State, Private \nBag X20539, Bloemfontein 9300, South Africa Abstract. The main aim of this paper is to assess the impact of regional \nclimate change scenarios on the availability of water resources in a semi-\narid river basin in South Africa using a hydrological model called Soil and \nWater Assessment Tool (SWAT). In this paper, climate change data was \nderived from two downscaling approaches, namely statistical downscaling \nexperiment (SDE) and dynamic downscaling (CORDEX). These were \nderived from the GCM simulations of the Coupled Model Inter-\ncomparison Project Phase-5 (CMIP5) and across two greenhouse gas \nemission scenarios known as Representative Concentration Pathways \n(RCP) 4.5 and 8.5. The spatial resolution of the dataset for the SDE \nmethod is 25 km × 25 km and 50 km × 50 km for the CORDEX method. Six GCM models were used for SDE set of data and four for the CORDEX \nset of data. SWAT model was run using these data for a period of up to \nmid-century (2020 – 2050) for SDE and for a period of up to the end of \nthis century (2020 – 2100) for CORDEX data. The results were then \ncompared with long-term historical data (1975-2005). Comparison of \nmeasured data with simulated historical data showed strong correlation (R2 \n= 0.95 for SDE data and R2 = 0.92 for CORDEX data), which is indicative \nof the reliability of projected future climate. 1 Introduction Water security is understood to be the availability of an acceptable quantity and quality \nof water for health, livelihoods, ecosystems and production, coupled with an acceptable \nlevel of water-related risks to people, the environment and economies [1]. The problem of \nwater scarcity is likely to deepen according to some projected climate change scenarios. It \nis projected that, by 2050, the Southern African region will be generally drier [2]. In \ngeneral, for South Africa there is a tendency towards a rise in temperature as evidenced in \nthe past five decades [3]. Maximum and minimum temperatures have also shown \nsignificant increases annually, and in almost all seasons. High temperature extremes have \nincreased significantly in frequency, and low temperatures have decreased significantly in \nfrequency annually and in most seasons across the country [2]. 2 Methodology The research focused on a semi-arid river basin in the central region of South Africa, \nknown as the Modder river basin. The Modder river basin is a large basin with a total area \nof 1.73 million hectares and divided into three sub-basins, namely the Upper Modder, the \nMiddle Modder and the Lower Modder. It is located within the Upper Orange Water \nManagement Area to the east of the city of Bloemfontein. The water supply to the middle \nand lower reaches of the Modder River is stabilized by two dams known as the Rustfontein \nand Mockes dams in the east, and by Krugersdrift Dam in the west of the city of \nBloemfontein. Climate change data was derived from two downscaling approaches, namely statistical \ndownscaling experiment (SDE) and dynamic downscaling (CORDEX). The downscaled \ndata were derived from the GCM simulations of the Coupled Model Inter-comparison \nProject Phase-5 (CMIP5) and across two greenhouse gas emission scenarios known as \nRepresentative Concentration Pathways (RCP) 4.5 and 8.5. The spatial resolution of the \ndataset for the SDE method is 25 km × 25 km and for the CORDEX method it is 50 km × \n50 km. Six GCM models were used for SDE set of data and four for the CORDEX set of \ndata. SWAT model was run using these data for a period of up to mid-century (2020 – \n2050) for SDE and for a period of up to the end of this century (2020 – 2100) for CORDEX \ndata. E3S Web of Conferences 98, 06014 (2019) \nWRI-16 Recent climate projections suggest a drop of up to 10% in precipitation in most of \nsouthern Africa by 2050 [4]. It is estimated that by the year 2025 almost one-half of the \nworld population will be living in water stressed regions [5], with rapid population increase, \nindustrialization and pollution putting further strain on the available and diminishing fresh \nwater resources. Within this context, there is a general consensus that development has to \nbe sustainable, adaptable and resilient to these global changes such as climate change. Resilient development involves initiatives that will deliver benefits under all potential \nfuture circumstances related to environmental changes [1]. Therefore, this calls for \ninnovative strategic approaches to deliver water security and resilient development. The \nmain aim of this paper is to investigate impact of climate change scenarios on water \nresources and water security. * Corresponding author: ywoyessa@cut.ac.za © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons \nAttribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1051/e3sconf/20199806014 E3S Web of Conferences 98, 06014 (2019) \nWRI-16 3 Results and Discussion Comparison of measured and simulated historical values are shown in Figures 1a and 1b for \nthe SDE approach and the CORDEX approach, respectively, for the period of 1975 to 2005. Figures 2a and 2b show the correlation between these values for SDE and CORDEX \napproaches over the same period. In Figures 2a and 2b, the blue points represent the \nobserved versus simulated values whereas the blue broken line shows the linear fit between \nthe observed and simulated values. The solid black line represents the one-to-one line (the \nperfect fit scenario). In both cases, the relationship between these two variables (measured \nand simulated historical values) are found to be strong with R2 > 0.92. The purpose of \nsimulating the historical data was to compare with climate observations over a common \nperiod and use information derived from the comparison to adjust future climate projections \nso that they are (progressively) more consistent with the historical climate records and, \npresumably, more realistic for the spatial domain of interest. 2 2 E3S Web of Conferences 98, 06014 (2019) E3S Web of Conferences 98, 06014 (2019) \nWRI-16 https://doi.org/10.1051/e3sconf/20199806014 ig. 1. Comparison of measured and simulated average historical monthly values of rain \nsing multimodel average: (a) SDE; (b) CORDEX. Fig. 1. Comparison of measured and simulated average historical monthly values of rain \nusing multimodel average: (a) SDE; (b) CORDEX. Fig. 1. Comparison of measured and simulated average historical monthly values of rain \nusing multimodel average: (a) SDE; (b) CORDEX. The projected decrease in rainfall is expected to have an impact on water balance \ncomponents of the river basin. The assessment of impact of climate change on water \nbalance components of the river basin showed varied results depending on the type of \nclimate model used and the downscaling approach, but generally, the trends were similar in \nmost cases (Figure 3a and 3b). In the case of the SDE approach, the multimodel average \nshowed a possible decrease in precipitation (by 14 %), a decrease in water yield (by 15 %) \nand an increase in potential evapotranspiration (by 10 %). A similar trend was observed for \nthe CORDEX approach, with a decrease in rainfall (by 3 %) and a decrease in water yield \n(by 13%) and an increase in evaporation (by 22 %). The increase in evaporation in both \ncases is indicative of possible drought spells between rainy events. 4 Conclusion The hydrological simulation as well as analysis of climate change data showed that there \nwill be a reduction in rainfall and other river basin water balance components under both \ngreenhouse gas emission scenarios, but the effect will be more pronounced under the \nRCP8.5. The expected decrease in rainfall coupled with increase in PET are going to be the \ntwo major drivers in exacerbating the existing problem of water scarcity in the region. For \nexample, decrease in rainfall (according to SDE’s approach) will result in the reduction of \nwater storage in a reservoir (Rustfontein Dam) by about 28% of its full capacity. If the 3 E3S Web of Conferences 98, 06014 (2019) https://doi.org/10.1051/e3sconf/20199806014 E3S Web of Conferences 98, 06014 (2019) \nWRI-16 increase in PET is added to this scenario, the effect will be much more pronounced and \nthere will be much more reduction in water storage. 2. Observed versus simulated average monthly values of rain using multimodel \nage: (a) SDE; (b) CORDEX. Climate change has direct impact on water resources. Similarly, the manageme\ner resources affects the vulnerability of ecosystems, socio-economic activities 2. Observed versus simulated average monthly values of rain using multimodel Fig. 2. Observed versus simulated average monthly values of rain using multimodel \naverage: (a) SDE; (b) CORDEX. Climate change has direct impact on water resources. Similarly, the management of \nwater resources affects the vulnerability of ecosystems, socio-economic activities and \nhuman health. Climate change is projected to lead to major changes in water availability \nwith increasing water scarcity and droughts mainly in the central region of South Africa. Water management is, therefore, expected to play an increasingly important role \nin adaptation to climate change. It is expected that the results of this research will assist in \nformulation of adaptation strategies that will minimize the negative impact of climate \nchange in the region. 4 E3S Web of Conferences 98, 06014 (2019) E3S Web of Conferences 98, 06014 (2019) \nWRI-16 https://doi.org/10.1051/e3sconf/20199806014 Fig. 3. Percentage change of future water balance components: (a) mid-century – SDE, (b) \nend of century – CORDEX. Fig. 3. Percentage change of future water balance components: (a) mid-century – SDE, (b) \nend of century – CORDEX. Fig. 3. Percentage change of future water balance components: (a) mid-century – SDE, (b) \nend of century – CORDEX. References 1. AMCOW, Water security and climate resilient development: Technical Background \nDocument (2012) 1. AMCOW, Water security and climate resilient development: Technical Background \nDocument (2012) 2. South African Department of Environmental Affairs, Climate trends and scenarios for \nSouth Africa, in Long Term Adaptation Scenarios (2013) 2. South African Department of Environmental Affairs, Climate trends and scenarios for \nSouth Africa, in Long Term Adaptation Scenarios (2013) 3. N. MacKellar, et al., South Afr J Sci, 110, 1-13 (2014) 3. N. MacKellar, et al., South Afr J Sci, 110, 1-13 (2014) 4. E. Levina, Domestic Policy Frameworks for Adaptation to Climate Change in the \nWater Sector Part II: Non-Annex I Countries. Lessons Learned from Mexico, India, \nArgentina and Zimbabwe, OECD, Paris (2006) 4. E. Levina, Domestic Policy Frameworks for Adaptation to Climate Change in the \nWater Sector Part II: Non-Annex I Countries. Lessons Learned from Mexico, India, \nArgentina and Zimbabwe, OECD, Paris (2006) 5. World Water Council, World Water Vision: Making Water Everybody’s Business, \nEarthscan Publications, London (2000) 5"