Water-Energy-Food Nexus Assessment Framework for Integrated Resource Management

Water, energy, and food (WEF) security are fundamental to human welfare and sustainable development, and WEF sectors are inevitably interconnected. Conventional sectoral policy- and decision-making in ‘silos’ may lead to unintended consequences to other sectors beyond objectives and scales or cause maladaptation. The uncertainty in climatic and socio-economic changes increases the level of complexity and challenges in WEF resources management. Addressing these issues calls for a “nexus” approach that aims to untangle interactions among sectors and identify opportunities to reduce trade-offs while building synergies to promote overall resource use efficiency, resource security, and policy coherence. This thesis aims to advance the understanding of integrated resource management, in particular, water, energy, and food, under historical conditions and future changes by proposing a comprehensive water-energy-food nexus assessment framework (WEFNAF). Three steps have been designed to achieve this goal. First, a WEF nexus model using the system dynamics approach has been developed. This model is applied to the Province of Saskatchewan, Canada, and so is named WEF-Sask. WEF-Sask captures the essential linkages and feedback loops among the water, energy, and food sectors, including water use for energy and agricultural (rainfed and irrigated) production, energy demand for agricultural activities and water supplies, and bio-crops (wheat and canola) for bioenergy production. The hydropower-irrigation trade-offs and synergetic benefits from the expanded use of other renewable energy sources are highlighted. Second, WEF-Sask is coupled with a climate downscaling tool and hydrological models to investigate the WEF nexus behavior under ensembles of hydroclimatic conditions and policy options. Based on preset agricultural and hydropower production targets or thresholds, favorable and unfavorable scenarios are identified and suggestions to improve the nexus performance are provided. Third, sector-specific adaptation strategies in the agriculture sector are proposed in response to potential hydroclimatic changes in the future, including agronomic measures and genetic improvements in crop cultivars. These strategies are evaluated from a WEF nexus perspective, including crop yield, water use efficiency (WUE), green and blue water use, associated energy demand for irrigation water supply and application, and impacts on hydropower production under uncertain hydroclimatic conditions. This thesis provides a set of insightful findings and suggestions for WEF nexus management. The WEF-Sask model shows overall good performance and has the potential to help investigate trade-offs and synergies as well as test response options or evaluate mitigation and adaptation strategies in response to changing hydroclimatic or socioeconomic conditions. Sensitivity analysis shows that crop production is highly sensitive to climate change, while socioeconomic factors (e.g., population, GDP, crude oil reserve/price, natural gas reserve/price) significantly affect the energy and water sectors as well as greenhouse gas emissions. In short, total water demand is most sensitive to population, air temperature, and precipitation. Future hydroclimatic changes cause uncertainty in the WEF nexus, and water deficit resulting from possible decreasing transboundary flows and local dry weather in Saskatchewan significantly threaten the WEF nexus performance. Moreover, irrigation expansion intensifies hydropower-irrigation trade-offs in dry conditions. Renewable energy expansion (wind power expansion and expanded use of bioenergy), the most effective climate change mitigation option in Saskatchewan, brings synergetic benefits by saving water from thermal power cooling and reducing greenhouse gas emissions. However, the expanded use of bioenergy (ethanol and biodiesel) in transportation is likely to significantly reduce wheat and canola surplus (export potential), resulting in trade-offs between sustainable energy and food. Climate characterized by a large increase in temperature with less rainfall will likely reduce agricultural production, to which it will be difficult to adapt; however, irrigation expansion can be employed to more easily adapt to climates characterized by a moderate temperature increase with slightly less rainfall or higher temperature increase with slightly higher rainfall. Additionally, the benefits of irrigation expansion in Saskatchewan for total food and feed production are likely to be fully offset by climate change. Therefore, it is of great importance to adopt mitigation strategies that slow down the global warming rate to make adaptations easier. Largely or fully offsetting agricultural production losses from climate change is unlikely to be achieved through individual adaptation strategies in the agriculture sector. Instead, combining individual strategies of earlier planting date, cultivars with a larger growing degree days requirement, and lower soil water evaporation can significantly compensate for the agricultural production losses from climate change and increase crop water use efficiency while mitigating the environmental burden (e.g., blue water use, energy consumption for irrigation) and hydropower-irrigation trade-offs. This result indicates that strategies involving effective water use, such as reducing soil water evaporation (alone or combined with other individual adaptation strategies), can benefit the overall food, water, and energy sectors. This strategy seems appropriate for water-scarce regions where large irrigation expansion is infeasible. Moreover, if irrigation expansion is also included, the agricultural production losses from climate change can be almost fully offset; however, this strategy requires considerable extra water and energy use for irrigation and a reduction in hydropower production.

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