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nevertheless represented half of global crop production (FAO 2016). Climate change effects on temperature and rainfall patterns may drive additional irrigation demands, with water scarcity in many parts possibly limiting crop yields by 2070 (Elliott et al. 2014). Efforts are under way worldwide to address predicted hydrologic changes, including shifts to more water- efficient irrigation technologies, while trade of agricultural products provides opportunities for improving food security and adjusting to water scarcity through food imports (United Nations 2017).


The quality and availability of irrigation water and irrigated land are projected to decrease concomitantly, with potential negative effects on food security and human health. About 34.2 million ha of irrigated area has been affected by salinization (Mateo-Sagasta and Burke 2012), representing 10 per cent of total irrigated area globally (324 million ha) (FAO 2017). About 60 per cent of irrigation water does not reach crops due to leakage, spillage and evaporation (FAO 2017), with losses being especially high in developing countries with poor irrigation infrastructure. Improved irrigation efficiency could make a substantial difference. The Mediterranean region could save 35 per cent of its irrigation water through efficiency improvements (Fader et al. 2016).


Food security and associated water demands are and will be further stressed by a growing population (FAO 2016). Changing food preferences with rising incomes also increases water demands, with livestock products being more water-intensive than crops. Global meat and dairy consumption are projected to increase by 89 per cent and 81 per cent, respectively, during 2002-2050, with higher growth rates in developing countries (Thornton 2010). However, use of drought-tolerant or flood- tolerant crops will be critical to improving the productivity of the agricultural industry with changing water supply conditions (Zandalinas et al. 2018).


The virtual water trade concept (i.e. water embedded in traded products ranging from crops to manufactured goods) illustrates the comparative advantages of certain water uses, including agriculture and energy, in particular regions (Gilmont et al. 2018). If water is appropriately priced and allocated, market forces can lead to overall efficiency by capitalizing on these advantages, with virtual water trade redistributing water efficiently, and partially helping to address the disconnect between consumption and production impacts (Mekonnen and Hoekstra 2011; Vörösmarty et al. 2015). However, water is not always priced and valued appropriately: water embedded in food commodities is controlled by supply chain corporations and international trade that neither account for ecosystem services nor costs of watershed degradation. The problem lies in the lack of accounting systems for water stewardship in market systems and the practice of subsidies and taxes to keep food prices low (Allan et al. 2015; Allan and Matthews 2016). Farmers are faced with the resulting pressures on food prices, further disempowering them from managing and sustaining water and ecosystems (Allan and Matthews 2016).


9.8.3 Human safety and security


Degraded water quality, physical and economic water scarcity, and loss of freshwater ecosystem services have significant impacts on human safety and security. Floods and droughts affect ever-larger numbers of vulnerable people (IPCC


2014), with security and migration implications magnified in transboundary basins.


Transboundary cooperation in addressing water scarcity, floods and droughts is challenging, but can enable more effective, efficient management and adaptation by pooling available data, models, scenarios and resources, and enlarging the planning space for locating adaptation measures, including transboundary basins (United Nations Economic Commission for Europe and International Network of Basin Organizations 2015). Transboundary water management creates benefits in international trade, climate change adaptation, economic growth, food security, and improved governance and regional integration.


About 286 international transboundary river basins involving 151 countries pose challenging management problems (UNEP-DHI Partnership and UNEP 2016), as do transboundary lakes and reservoirs. Further, there are currently 366 identified transboundary aquifers and 226 transboundary ‘groundwater bodies’ underlying almost every nation (International Groundwater Resources Assessment Centre and United Nations Educational Scientific and Cultural Organization - International Hydrological Programme 2015). Even within federated countries (e.g. Australia, India, the United States of America), transboundary problems may be no less acute at a state/provincial level. Although water management has historically led to cooperative, rather than conflicting, outcomes, significant conflicts between stakeholders can still occur over the implementation of international and inter-state agreements. Intensification of water pollution and water scarcity can cause tensions within and between nations, though rarely being the sole trigger of conflict, since a complex mix of social and political conflicts, economic, demographic and environmental factors, and military occupation and water wars (hegemony) is typically the origin of such conflicts.


9.9 Policy responses


Human activities now dominate changes in the biosphere and functioning of the Earth system (Green et al. 2015; Vörösmarty, Meybeck and Pastore 2015; Vörösmarty et al. 2015), “causing complex, and frequently unwanted outcomes including unprecedented changes to global water circulation” (Bhaduri et al. 2016).


Box 9.3: Jordan faces a combined refugee and water crisis


Jordan is one of the world’s most water-scarce countries, providing only 150 m3 lower than the 1,000 m3


of water annually per person, much /capita level denoting water scarcity.


Jordan also currently hosts over 717,000 Syrian and Iraqi refugees, adding to freshwater supply pressures. The formerly permanent lush Azraq Oasis in Jordan used to cover more than 6,000 ha, supporting a variety of plant and animal life, including migratory birds, as well as being the main water source for Jordan’s capital city, Amman. However, it was almost completely dried out by 1990, due to overexploitation of the underlying aquifer. By 2017, there were over 35,000 refugees living in the Azraq refugee camp in the oasis (United Nations High Commissioner for Refugees [UNHCR] 2017), an unsustainable situation contributing to further water stress (Alhajahmad and Lockhart 2017).


9


Freshwater


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