Water-Food-Energy Nexus in Transboundary River Basins
Date: 28 September 2020
University of Exeter
PhD in Engineering
Water, food and energy are fundamental for achieving our social, economic and environmental goals. The three domains are inextricably linked and the action in one sector could affect the two other sectors. Achieving the Water, Food and Energy (WFE) nexus balance and improving long-term sustainability through policy interventions is ...
Water, food and energy are fundamental for achieving our social, economic and environmental goals. The three domains are inextricably linked and the action in one sector could affect the two other sectors. Achieving the Water, Food and Energy (WFE) nexus balance and improving long-term sustainability through policy interventions is particularly challenging in transboundary river basins because of the dynamic nature and inter-sectoral complexity that may cross borders. Increased pressure from population growth, urbanization and economic growth in riparian countries induce each riparian country to maximise its resources to meet growing water, food and energy demands. Such infrastructure developments and policies in riparian countries could result in basin-wide cooperation or trigger conflicts among the countries. What is more, climate change is likely to exacerbate the risks associated with the hydrologic regime and affect the livelihoods in river basins. The “nexus thinking” shifts the focus from one sector-centric towards multi-centric analytical frameworks to better understand the complexity and improve the management of disparate but interconnected sub-systems. This thesis builds upon the nexus approach and develops a novel systems-based approach to better understand the nexus interactions while considering other related important issues such as long-term uncertainty in river flow regime, socio-economic development, climate change and policy choices in river basins. The framework considers a biophysical water resource model of the river basin and integrated with an agricultural land and crop yield models to account for food production. The energy component includes hydropower generation from the system’s hydropower plants, while energy demand is accounted for energy requirements in water and food sectors. To account for the uncertainty in hydrologic river regime and large variability of the river flows, stochastic simulation is adopted with and without climate change. The population size and Gross Domestic Product (GDP) per capita represent socio-economic characteristics. The water resource model can accommodate future planned infrastructure projects and policies, e.g., improving irrigation efficiency, in the basin. The novel framework is applied for the Nile river basin as a case study. The Nile River basin is a transboundary river basin in East Africa shared by eleven countries and home for about 250 million people. The riparian countries have devised ambitious master plans to utilise potential resources in the basin to meet the growing water, food and energy demands of their populations and sustain their expanding economies. The Nile is vulnerable to climate change that is likely to add further uncertainties to the hydrologic river regime. The – near completion – Grand Ethiopian Renaissance Dam (GERD) is the largest development in the basin and has the potential to deliver regional economic benefits and improve regional cooperation. However, it also has raised regional tensions – between Egypt, Ethiopia and Sudan – which have gained international attention and could hinder the livelihoods in downstream countries. A System Dynamics model was built for the entire Nile basin to explore the WFE nexus in the basin. The integrated simulation model considers a complete WFE nexus for Egypt while partial consideration for the rest of the countries. The integrated simulation model consists of two main components: (a) partial WFE nexus outside Egypt and (b) complete WFE nexus in Egypt. The two model components are linked through High Aswan Dam (HAD). The first component consists of a water resource model for the entire Nile basin with 72 basin-wide river inflow tributaries. The Nile water resource model incorporates key components that affect the system’s water management such as natural lakes, wetlands, water infrastructure (e.g., dams) and different water users. A simple crop yield model is linked to the Nile water resource model to account for food production from irrigated agriculture in the basin. Hydropower generation can be obtained from hydropower plants in the basin during model simulations. The second component, i.e., complete WFE nexus in Egypt, includes population, gross domestic product, water balance and food balance, while the energy sector includes hydropower generation from HAD and energy demand in food and water sectors. To account for the uncertainty and hydrologic variability in river flow regime, a stochastic simulation is applied. Model simulations are driven by basin-wide stochastically generated data that is either based on historical stream flows (for the case of no climate change) or climate change projection of stream flows (for the case of climate change). The integrated simulation model runs at a monthly time-step. Model calibration and validation showed a satisfactory performance and the model is fit for the purpose for which it is developed. The integrated simulation model was used to investigate the WFE nexus in the basin during the filling and subsequent operation of GERD using basin-wide stochastically generated river flows with no climate change. Results show that GERD filling during above-average years is likely to have a little impact on the downstream countries and it could accelerate the reservoir filling. Conversely, the reservoir filling during dry years is likely to cause significant impacts on the downstream countries. Once GERD comes online, it will generate an average of 15,000 GWh/year. Furthermore, model simulation results suggest further investigation and implementation of dynamic filling strategies that would maximize basin-wide benefits and reduce risks to downstream countries. At the national level, the developed model was used to investigate the impacts of implementing policy measures (e.g., improving irrigation efficiency, developing new water resources, improving land productivity) on the WFE nexus in Egypt. For instance, improving irrigation efficiency and land productivity offer promising outcomes to improve the future of the WFE nexus in Egypt. For instance, achieving the potential crop yields alone would increase food production by 40% and reduce food imports by 32%. The simulation model is also used to explore the cooperation over the GERD and its impacts on the WFE nexus on the downstream countries during the operation phase. Simulation results show that during dry years, the risks to Egypt (e.g., water shortages and food production loss) can be substantially reduced if the riparian countries agree to cooperate and sacrifice for some loss (i.e., loss in hydropower generation) especially during severe droughts. However, a high level of coordination, commitment and trust among the riparian countries are urgently required to achieve cooperation benefits. Basin-wide impacts of planned projects in the riparian countries are also analysed through different developments scenarios (e.g., hydropower development scenario, hydropower and irrigation expansions scenario) with and without climate change. Climate change is investigated here through two Representative Concentration Pathways (RCPs): RCP 8.5 and RCP 4.5 with two General Circulation Models (GCMs) per each climate scenario until 2050. Projected streamflow of river tributaries under climate change are used to generate basin-wide synthetic streamflow series to drive model simulations. Simulation results demonstrate that the WFE nexus in the basin is less affected by planned developments than climate change. The analysis of climate change scenarios indicated that climate change exhibits large uncertainty and is likely to have significant impacts on the river flow regime, food production and hydropower generation in the basin. The average annual river runoff is likely to reduce by 7% in the RCP 4.5, while RCP 8.5 showed a wider range of change from -40% to +33%. Following river flow changes, hydropower generation and food production in the basin are impacted in a similar way under climate change but with varying degree of change in sub-basins. At the general level, the novel framework developed in this work is a step forward for better understanding of the nexus interdependencies in river basins including but not limited to the challenging case of transboundary rivers. The novel framework addressed key nexus interlinkages and considered important issues such as uncertainty in river flow regimes, climate change and population growth. It can be beneficial in negotiations for transboundary systems, policy analysis, enhancing cooperation and trust among riparian countries, and promoting for cross-sectoral and cross-regional management. Systems-based approaches offer basis to improve our understanding of the interactions between the WFE nexus and other important issues in river basins. Furthermore, they allow for identifying trade-offs and synergies and improve coordination among sectors, countries and interested stakeholders.
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