The complexity of sociohydrological dynamics, the variability of institutional settings, and the inter dependencies of water with other key dimensions, such as food and energy, could benefit from innovative adaptive governance approaches .The idea that the development of water infrastructure is important to economic development has often been considered as a corollary to classical models of economic development postulating the need for “growth” in the agricultural sector, followed by the development of industry and services . The rationale for this growth model is that investments in water infrastructure are required to develop irrigation systems that would lead to higher crop yields . It has been argued that in some developing countries, economic development has been impeded by strong intra-annual and inter annual variability in hydrologic conditions that expose crops to often unpredictable water stress; therefore, investments in water infrastructures are urgently needed across the developing world . Even though these claims have not been conclusively supported by data, they are often invoked to advocate for new investments in dams and other “gray” infrastructures, such as canals, pipelines, or other hydraulic structures . This model of economic development, however, remains controversial because such infrastructures could cause irreversible environmental damage and often serve the needs of large-scale commercial agribusinesses rather than subsistence farmers, whereas green approaches, based on water harvesting, small farm-scale ponds,potted blueberries and new crop water management techniques with low evaporative losses of water are likely more effective and less costly .
Recent research on this topic has highlighted the benefit of building small decentralized water harvestings and storage facilities as a sounder and economically more viable alternative to large dams . Indeed, farm-scale reservoirs and small retention ponds better suited for decentralized approaches to water management are more likely to serve small-scale farmers and reduce the cost of conveyance and distribution systems .Human activities require energy to power systems of production, transportation, heating, and cooling . In preindustrial societies energy options were relatively limited and mainly consisted of wood burning and draft animals , which in turn required land and water for the production of fuel wood or fodder. Thus, land and water availability constrained energy production in the preindustrial world . The industrial revolution provided unprecedented access to power with engines fueled by fossil materials that required almost no land or water . After 1950, there was a massive energy transition in the “Great Acceleration” period, with particularly large increases in fossil fuel-based energy systems . This transition toward a high-energy society after 1950 coincided with dramatic socioeconomic changes, including increased agricultural production , as well as an increased rate of manufacturing, economic growth, urbanization, and demographic growth . Such trends occurred along with a reduction in the amount of labor effort needed by the societal metabolism, that is, the way materials and energy are exchanged within societies, among societies, and between societies and nature . The benefits of the increasing reliance on fossil fuels, however, came at the cost of burning, in just a few decades, much of the readily available oil and gas, thereby depriving future generations of these energy options. At the same time, fossil fuel consumption increased atmospheric CO2 concentrations with important impacts on the global climate . Today the energy system suffers from major problems that are a legacy from the twentieth century: energy consumption mostly relies on nonrenewable sources and increases as a result of population and economic growth, while about 3 billion people have no access to safe and reliable energy sources.
In year 2017, 2.8 billion people relied on biomass, coal, or kerosene for cooking . Household air pollution from these sources is linked to millions of premature deaths, along with health and environmental impacts on local communities . Moreover, across the developing world several billion hours are spent every year collecting fire wood for cooking, mostly by women. This time could be put to more productive uses such as education . The ongoing continued reliance on fossil fuels is a major contributor to GHG emissions, air pollution, and associated health and environmental problems . In recent years, there has been a big push for the development of more efficient systems of energy production from renewable sources, such as solar and wind power . Societies will likely increasingly rely on renewable energy and gradually reduce dependence on fossil fuels . In the meantime, however, humanity needs to deal with the challenge of curbing CO2 emissions, while removing inequalities in the access to energy. To date, one in five people still lack access to modern electricity in their homes; three billion people use wood, coal, charcoal, or animal waste for heating and cooking . Access to affordable, clean, and reliable energy, which is listed as one of the UN’s SDGs , is a major challenge of our time. Achieving this goal and, more generally, enhancing energy security—defined as “the uninterrupted availability of energy sources at an affordable price” —requires improvements to the systems of energy production and distribution that may ultimately exacerbate competition for water with agriculture, as explained in sections 7 and 8.Seafood production includes a wide range of species groups , production environments , and production methods . Since seafood species are, by definition, aquatic organisms, seafood production is intimately related to water resources. However, water-resource requirements for seafood production are as varied as the species produced and the production methods used . Aquaculture is currently the fastest growing production component in the global food system , and as much as one half of seafood consumption is now derived from farmed fish . Water use for aquaculture is similar to that for terrestrial food production, such as water use for feeds, but water use for aquaculture differs owing to its large water storage requirements.
Aquaculture feed dependence varies by species, with some species requiring essentially no aqua feeds and others relying almost completely on feeds . The water footprint of aqua feeds varies depending on feed composition, which varies by species and time on the basis of the prices of different ingredients . Recently, efforts have been made to replace fish meal and fish oil in aqua feeds with crop-based ingredients in order to improve the sustainability of aquaculture by supplanting the use of capture fisheries for the production of aqua feed based on fish meal and fish oil . While a shift toward crop-based aqua feeds may reduce pressures on wild fisheries, it also increasingly links seafood consumption to terrestrial agriculture. This shift in feed source may have a trade-off with water use though because production of crop-based feeds typically uses more water than the production of fish meal and fish oil . Large water storage requirements for aquaculture differentiates the water use types and processes that are most relevant for aquaculture from those relevant for agriculture or livestock farming . Water storage creates a competitive use for water resources, alters the rates and timing of evaporation and seepage, and can involve large quantities of in situ water use . In situ water use is essential for providing habitat for inland capture fisheries, and minimum environmental flows are needed to maintain appropriate salinity levels in brackish water ecosystems. Although crucial for these capture fisheries and some forms of aquaculture,square plastic pot in situ water use can be difficult to quantify and cannot be directly compared to consumptive water use in agriculture systems. Despite these methodological challenges, as the seafood sector grows , it is increasingly important to consider water use for seafood production.Water and energy are interconnected, largely in terms of the water use involved in power generation but also indirectly as a result of hydrological alterations associated with hydro power development . Fuel production and power generation rely on water availability, and the supply of water requires energy . Both water and energy are finite resources that, in a rapidly changing world, are set to be placed under increasing stress. New energy technologies implemented to “decarbonize” the economy of industrial societies are increasing our reliance on water-intensive fuels , further exacerbating the interconnection between energy production and water resources. For example, bio-fuel production, concentrating solar power , and carbon capture and storage require large amounts of water. Thus, water availability may challenge existing energy operations and is increasingly recognized as a factor determining the physical, economic, and environmental viability of energy production projects.The rising importance of the water-energy nexus has been recognized by the IEA’s World Energy Outlook . Moreover, the energy sector is increasingly concerned about the effects of climate change on the water cycle. More than three quarters of the world’s top energy companies indicate that uncertainty in water availability is a major source of risk for their business operations . Water shortages have already caused the shutdown of coal-fired power plants in India and are affecting the choice of location and technology used for energy projects in China . In south Texas, shale oil and gas extraction using hydraulic fracturing has competed for water with agriculture through a water market, thereby increasing water prices in the region .
Years of drought in the State of California have reduced the hydro power share of total energy production from 30% to 5% . Dam construction is another rapidly evolving nexus issue for the food-water nexus and the energy-water nexus . On the one hand, dam construction can have significant economic benefits in addition to supplying renewable energy . However, these benefits can come at substantial social and environmental costs in some river basins . Dam construction alters natural flow regimes and the connectivity of river systems, which can disrupt the movement of organisms and sediment, whereas water storage associated with dam operations regulates river flow, which can alter geomorphic processes and disrupt ecological functions both upstream and downstream . Hydropower generation is influenced by the year-to-year variations in rainfall that increase the risk of climate-related electricity supply disruption in dry years . While thousands of hydropower dams are planned or currently under construction globally , three large river basins have particularly large numbers of hydropower dam projects and collectively hold about one third of freshwater fish species . The Mekong contains the world’s largest inland fisheries, which are an important source of food for local populations. These fisheries are particularly sensitive to dam construction because of disruptions of migratory fish stocks .Water use for crude oil production greatly varies, depending on technology used, local geology of the reservoir, and operational factors . Relatively large amounts of “fossil” water, corresponding to roughly 7 times the volume of oil produced, are extracted with the oil . The produced water is injected into disposal wells, reinjected into the reservoir to improve oil recovery efficiencies, or treated with energy-intensive technologies and added to the water cycle.Primary oil recovery, that is, the natural flow of oil into production wells, has a small water footprint of extraction. However, primary recovery usually extracts less than one third of the hydrocarbons stored in the geologic formation from which they are extracted. To maximize reservoir production, more expensive and advanced technologies, such as secondary and tertiary oil recovery, are implemented. Secondary recovery via water injection uses large amounts of water to improve oil production. Water allocations can come from different sources; for example, in Russia, water is withdrawn from freshwater resources, and in Saudi Arabia, the water used is typically either brackish water or seawater . Tertiary oil recovery or enhanced oil recovery via thermal recovery is even more costly and energy demanding. In this case, high-pressure steam is injected into the hydrocarbon reservoir to reduce heavy oil viscosity and increase the production flux. Another water-intensive enhanced oil recovery technique is tertiary recovery via CO2 injection. CO2 is captured from the “flue” gas emitted using water-based technologies, such as absorption through amine scrubbing . Carbon dioxide is subsequently stripped from the solvent by heating and transported and injected into the hydrocarbon reservoir to enhance oil production . In recent years unconventional fossil fuels have received increased attention as important energy sources . Shale oil and oil sands are expected to contribute to a growing share of our future energy needs.