The aim of this paper is to provide policy-makers with a helpful overview of the technical and economic aspects of water use in agriculture, with particular emphasis on crop and livestock production. Through 2050, in many countries, agriculture will remain an important determinant of economic growth, poverty reduction, and food security, even as, over time, the proportion of agricultural revenue in national gross income declines. Water use in agriculture will remain substantial, irrigated areas will expand and competition for water will increase in all sectors. Most likely, overall supplies of land and water will be sufficient to achieve global food production goals in 2050; although poverty and food insecurity will remain pressing challenges in several regions and countries. Thus, the focus of this report is on the regional and national aspects of food security.

Global challenges have exacerbated a search for solutions to poverty and environmental degradation. Integration it was argued would help address the twin challenge. Integrated Water Resources Management (IWRM) was supposed to be that magic bullet and was embraced by scientists because of the clinical efficiency with which it argued for integrated analysis of sectors and resources and of systems and scale conditions. This paper argues that effective implementation of the Water-Energy-Food (WEF) Nexus can be supported by robust science. The corollary that robust science automatically leads to effective implementation is not always known to be true. The nexus approach sheds light on the challenges of implementation by introducing concepts of trade-offs and thresholds and consequently emphasizes the importance of transdisciplinary approaches to sustainable development. This paper reviews the results of recent research to offer tentative answers to the following questions: (a) Why is the governance dimension important to undertake an integrated analysis of water-energy-food challenges? (b) What does the nexus approach connote in normative and institutional terms? (c) What does implementation mean in nexus terms? (d) How can we establish if the nexus approach is an improvement over business as usual? and (e) What tools are available that would enable translation of results of scientific research to create an evidence base that would enable decision makers to act in support of sustainable development?

Throughout the world, much food produced is wasted. The resource impact of producing wasted food is substantial; however, little is known about the energy and water consumed in managing food waste after it has been disposed. Herein, we characterize food waste within the Food-Energy-Water (FEW) nexus and parse the differential FEW effects of producing uneaten food and managing food loss and waste. We find that various food waste management options, such as waste prevention, landfilling, composting, anaerobic digestion, and incineration, present variable pathways for FEW impacts and opportunities. Furthermore, comprehensive sustainable management of food waste will involve varied mechanisms and actors at multiple levels of governance and at the level of individual consumers. To address the complex food waste problem, we therefore propose a “food-waste-systems” approach to optimize resources within the FEW nexus. Such a framework may be applied to devise strategies that, for instance, minimize the amount of edible food that is wasted, foster efficient use of energy and water in the food production process, and simultaneously reduce pollution externalities and create opportunities from recycled energy and nutrients. Characterization of FEW nexus impacts of wasted food, including descriptions of dynamic feedback behaviors, presents a significant research gap and a priority for future work. Large-scale decision making requires more complete understanding of food waste and its management within the FEW nexus, particularly regarding post-disposal impacts related to water.

Population growth, increasing demands for food, ever-growing competition for water, reduced supply reliability, climate change and climate uncertainty and droughts, decline in critical ecosystems services, competition for land use, changing regulatory environments, and less participatory water resources governance are contributing to increasing difficulties and challenges in water resource management for agriculture and food. The need for sustainable food security for our global population and the need for preserving the environment, namely natural and man-made ecosystems and landscapes, have created an increased need for integrated, participative and scalable solutions focusing the various levels of irrigation and nature water management, from the field crop to the catchment and basin scales. Meanwhile, challenges and issues relative to water management for agriculture and food have evolved enormously in the last 30 years and the role of active management of the components of the water cycle is assuming an increased importance since their dynamics are key to assure water use sustainability, mainly agriculture and natural ecosystems sustainability. However, different regions face context-specific challenges associated with water scarcity, climate, governance, and population requirements. The main and first challenge is producing enough food for a growing population, which is intimately related with challenges placed to agricultural water management, mainly irrigation management. This paper revises challenges and progress achieved in the last 30 years focusing on irrigated agriculture, mainly water management, and its contribution to food security and the welfare of rural communities.

Food and water security have moved to the top of the global agenda following the food and energy price increases that started in 2007. Addressing the food, water and energy nexus is considered increasingly important for transparently and equitably meeting increasing global demand without compromising sustainability. This paper argues that given the unique regional and sector challenges of food, water and energy security, their nexus must be deconstructed to find effective, contextualized solutions. And governance challenges are at the heart of the nexus in each region. Governance is defined in various ways, but, with a few notable exceptions, the definitions have undergone relatively little analysis. In turn, governance issues are imbedded in policy, institutional, technological and financing options exercised at the global, regional, national and local levels. Furthermore, strong interactions between levels prompt policy responses to specific events and outcomes. The cu rent governance arrangements, where they exist at all, are woefully inadequate to address the challenges. They are imbedded in a lack of strategic clarity, and among stakeholders there is an unequal distribution of power, voice and access to information, resources and the capability to exercise a sound influence which will produce equitable and sustainable outcomes. Often there are huge tradeoffs between the short-term wins of individual stakeholders and long-term holistic solutions. This paper uses illustrative examples from recent global developments, as well as from China and India, to make the case for placing empirical analysis of governance issues at the top of the global agenda. At each level, governance is ues affect the choice of policies, institutions and outcomes for addressing these daunting challenges.

Researchers and practitioners have developed many tools to study the water-energy-food nexus at a variety of scales and perspectives in order to aid decision-making. However, there is a recognised lack of tools that consider these interdependent and complex interactions in an integrated fashion. Whether to connect and federate wellestablished modelling systems and approaches, which may be challenging, or to design truly integrated tools for holistic consideration of the nexus issues, is also debated. This paper discusses four distinctly different approaches which appear to have wide-scale applicability, although demonstration of these approaches in multiple cases (besides the Polestar model which is already regional/ global) is yet to be applied. Sustainable implementation of any tools will require greater accessibility such that they may be more widely deployed by practitioners. Harmonisation of results and insights between different scales, so that decision-makers may consider global-local impacts, also remains a challenge.

Summary (En)

For a water-secure present and future, there is a need for a transition from water scarcity towards water security. This transition necessitates a look at the complex relationships, and interdependencies, between water and other resources, and the institutions governing them. Nexus approach encompasses these interdependencies. This paper focused on the water–food nexus through the lens of the virtual water (VW) flows concept with the aim to explore the role of the VW flows concept in governing the transition towards water security in a water-scarce economy like India. The key findings of the paper suggests that the highest VW outflows are from highly water-scarce states of India, such as Punjab and Andhra Pradesh, and the moderate to highly water-scarce state West Bengal from 1996–2014. Major VW outflows from these states are to other highly water-scarce states, resulting in the concentration of water scarcity. The main priorities for the governance of the water–food nexus in these states emerge from policies and action plans. These priorities are groundwater overexploitation, water and soil pollution, and uncertainty in rainfall and are linked to agricultural intensification. The water footprint-based VW flow analysis has important insights for sustainable intensification of agriculture, and rectification of the unsustainable VW flow patterns. The study concludes that the VW flows concept embodies the water–food nexus and is particularly relevant for the sustainable future of developing and emerging economies, such as India, grappling with water scarcity and challenges of fragmented environmental governance systems.

This article summarizes some major factors that influence the Water–Energy–Food (W–E–F) Security Nexus and how they are perceived in different basins. These findings are based on a survey that was undertaken for the Global Catchment Initiative (GCI) within the Global Water System Project (GWSP) complemented by case studies for a transboundary basin (the Lake Winnipeg Basin), a national basin (Yellow Basin in China), and a number of the basins in a nation (India). The analysis also includes ranking of river basin issues related to the WEF Nexus based on the views of experts in nine basins. Based on this analysis, factors that have affected the evolution of the W–E–F Nexus, including the applications of Earth observations, are discussed. The study concludes that the W–E–F Nexus could be an effective vehicle for advancing water and sustainability issues and recommends research and demonstration projects to test the extent to which the WEF framework could be helpful in increasing understanding and collaborative governance approaches.