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.

The Earth’s population is expected to exceed 9 billion by 2050, posing significant challenges in meeting human needs while minimally affecting the environment. To support this population, we will need secure and safe sources of food, energy, and water. The nexus of food, energy, and water is one of the most complex, yet critical, issues that face society. There is no more land to exploit, and the supply of fresh water in some areas of the world limits the use of land for food. All solutions must also deal with the overlay of global climate change. Meeting current and future populations needs will require security in food, energy, and water supplies. A nexus approach is needed to improve food, energy, and water security integrating the management of the limited resources while transitioning to a more “green” economy, which provides adequate food, energy, and water for the expanding human population.

This study evaluated the comprehensive Water-Energy-Food-Carbon Nexus (WEFC) by focusing on energy assessment in northwest Iran. The energy evaluation indices for different products were calculated by estimating the total input and output energies. Multi-objective optimization based on five individual objectives and WEFC Nexus policies was used to identify the optimal land-use allocation of wheat, barley, rapeseed, and sugar beet, silage corn, and potato while minimizing water and energy consumption and CO2 emissions, and maximizing food production and profit. The results indicate that the suggested framework provides a practical methodology for determining the optimal land-use allocation considering quantitative WEFC Nexus. To increase economic efficiency and reduce energy consumption, agricultural practices and policy recommendations should be adopted, including promoting renewable energy sources, implementing energy-saving technologies, improving fertilizer management, improving crop rotation practices, conservation tillage, and improving water management and adoption of sustainable farming practices. The results allow policymakers to optimize multiple resources and recommend the best resource allocation under recommendation policy, technology, and constraints to achieve sustainable development in agriculture.

Global population growth exerts stresses on river basins that provide food, water, energy and other ecosystem services. In some basins, evidence is emerging of failures to satisfy these demands. This paper assembles data from nine river basins in a framework that relates water and food systems to development. The framework provides a consistent basis for analysis of the water and food problem globally, while providing insight into specific conditions within basins. The authors find that successes occur when demand is met by increased productivity, while failure occurs when factors conspire to prevent development of land and water resources.

According to estimates by the International Land Coalition based at the International Fund for Agricultural Development (IFAD), 57 million hectares of land have been leased to foreign investors since 2007. Current research has focused on human rights issues related to inward investment in land but has been ignorant of water resource issues and the challenges of managing scarce water. This handbook will be the first to address inward investment in land and its impact on water resources in Africa. The geographical scope of this book will be the African continent, where land has attracted the attention of risk-taking investors because much land is under-utilised marginalized land, with associated water resources and rapidly growing domestic food markets. The successful implementation of investment strategies in African agriculture could determine the future of more than one billion people. An important factor to note is that sub-Saharan Africa will, of all the continents, be hit hardest by climate change, population growth and food insecurity. Sensible investment in agriculture is therefore needed, however, at what costs and at whose expense? The book will also address the livelihoods theme and provide a holistic analysis of land and water grabbing in sub-Saharan Africa. Four other themes will addressed: politics, economics, the environment and the history of land investments in sub-Saharan Africa. The editors have involved a highly diverse group of expert researchers, who will review the pro- and anti-investment arguments, geopolitics, the role of capitalist investors, the environmental contexts and the political implications of, and reasons for, leasing millions of hectares in sub-Saharan Africa. To date, there has been no attempt to review land investments through a suite of different lenses, thus this handbook will differ significantly from existing research and publication.

Earthquakes often cause destructive and unpredictable changes that can affect local hydrology (e.g. groundwater elevation or reduction) and thus disrupt land uses and human activities. Prolific agricultural regions overlie seismically active areas, emphasizing the importance to improve our understanding and monitoring of hydrologic and agricultural systems following a seismic event. A thorough data collection is necessary for adequate post-earthquake crop management response; however, the large spatial extent of earthquake's impact makes challenging the collection of robust data sets for identifying locations and magnitude of these impacts. Observing hydrologic responses to earthquakes is not a novel concept, yet there is a lack of methods and tools for assessing earthquake's impacts upon the regional hydrology and agricultural systems. The objective of this paper is to describe how remote sensing imagery, methods and tools allow detecting crop responses and damage incurred after earthquakes because a change in the regional hydrology. Many remote sensing datasets are long archived with extensive coverage and with well-documented methods to assess plant-water relations. We thus connect remote sensing of plant water relations to its utility in agriculture using a post-earthquake agrohydrologic remote sensing (PEARS) framework; specifically in agro-hydrologic relationships associated with recent earthquake events that will lead to improved water management.

The argument that economies that face acute water scarcity problems can and should meet their water demand for food through cereal imports from water-rich countries; and that virtual water trade can be used to achieve water securities has become dominant in global water discussions. Analysis of country level data on renewable freshwater availability and net virtual water trade of 146 nations across the world shows that a country's virtual water trade is not determined by its water situation. Some countries have the advantage of high "economic efficiency" in food production and have surplus water, but resort to food import, whereas some water scarce countries achieve high virtual water trade balances. Further analysis with a set of 131 countries showed that virtual water trade increased with increase in gross cropped area. This is because of two reasons: First, when access to arable land increases, the ability to utilize available blue water for irrigation increases. Second, increasing access to arable land improves the access to water held in the soil profile as "free good", a factor not taken into account in assessing water availability. Hence, many of the humid, water-rich countries will not be in a position to produce surplus food and feed the water scarce nations; and virtual water often flows out of water-poor, land rich countries to land-poor water-rich countries. This means that "distribution of scarcity" and "global water use efficiency", are goals that are difficult to achieve through virtual water trade in a practical sense. For a water-poor, but land rich country, virtual water import offer little scope as a sound water management strategy as what is often achieved through virtual water trade is improved "global land use efficiency". The important policy inferences emerging from the analyses are two: First, assessing the food security challenges posed to nations in future purely from a water resource perspective provides a distorted view of the food security scenario. National policies on food security should take into account "access to arable land" apart from water availability. Second, analysis of water challenges posed by nations purely from the point of view of renewable water availability and aggregate demands will be dangerous. Access to water in the soil profile, which is determined by access to arable land, would be an important determinant of effective water availability.