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Too much rainfall brings pollution, soil erosion, avalanches and mud slides which, together with floods, tornadoes and cyclones, are responsible for much physical damage to infrastructure, loss of life and injury. Too little rainfall causes drought, extreme wildfires, sandstorms, soil degradation and increased competition over water sources, often leading to the accelerated shrinkage and loss of these goods. Collectively, these realities and risks have grave socio-political, economic, environmental and ecological implications, making better management and governance of freshwater resources an imperative.


9.3 Water and land use 9


Growing cities and agricultural intensification are increasingly depleting both surface water and aquifers. Wetlands are being drained, and many rivers, lakes and ponds are vanishing in water- scarce regions. Land-use changes result in surface hardening of natural areas, reducing infiltration and aquifer recharge, while increasing water run-off and pollution. Land degradation and deforestation also cause increased run-off, carrying eroded sediment through rivers into oceans (see Section 8.4.2). In areas experiencing large-scale deforestation, the likelihood of precipitation events is decreasing and soil erosion is increasing (Birkinshaw et al. 2011; Ellison, Futter and Bishop 2012).


Agriculture is responsible for an average 70 per cent of global water withdrawals (UN-Water 2017). Industrial processes and energy generation increasingly compete with agriculture and cities for available water. However, much energy water demand is for non-consumptive uses (e.g. cooling) (UNEP 2012a).


The interconnections between water, energy security and food security have identified tensions and trade-offs between them requiring careful scrutiny and consideration (Rosengrant et al. 2009). This nexus becomes especially important when considering drivers such as urbanization, population, economic growth, technology and innovation (Bleischwitz et al. 2018).


9.4 Global state and trends of freshwater 9.4.1 Water quantity


Geographic variations, coupled with climate change, result in uneven distribution of rainfall and freshwater sources, with deserts and rainforests highlighting these water availability extremes (Figure 9.1 and Figure 9.4). Groundwater is the major drinking water source for the majority of people globally, particularly in arid regions and during drought. The estimated available renewable groundwater resource in Africa is more than 100 times that of total annual renewable surface-water resources (MacDonald et al. 2012, p. 5). However, deeper aquifer water is constrained by exploration and abstraction costs. Abstraction of very ancient ‘fossil groundwater’ is unsustainable, because this is not a renewable resource.


9.4.2 Water withdrawals


Human and environmental water demands vary spatially and culturally across rural and urban areas. While an average of 70 per cent of water withdrawals worldwide are for the agricultural sector, this varies widely across regions and countries (Hoekstra and Mekonnen 2012, p. 3232; Food and Agriculture Organization of the United Nations [FAO] 2016;


240 State of the Global Environment


UN-Water 2017). South-East Asia uses more than 80 per cent of its available freshwater for agriculture (FAO 2016).


The North American region has the highest per capita freshwater use (Hoekstra and Mekonnen 2012, p. 3232; UNEP 2016a, p. 71), although increased water-use efficiency is helping to lower demand, despite population and economic growth (UNEP 2016a, p. 71). Water withdrawals by all sectors in the United States of America (Figure 9.3) illustrate high water usage for cooling in electricity production.


Groundwater is increasingly important globally, representing estimated withdrawals of about 982 km3


(Margat and van


der Gun 2013), equivalent to nearly 33 per cent of total water withdrawals (Seibert et al. 2010, p. 1863; Famiglietti 2014, p. 945). Since conventional groundwater withdrawal technology is easily accessible to landowners, extraction is highly decentralized. Groundwater in confined artesian basins (Bundesanstalt für Geowissenschaften und Rohstoffe [BGR] 2008) can be accessed at depths of up to 2 km, and often provides a strategic water resource, especially during droughts (e.g. Great Artesian Basin, Australia [GABCC] 2016); Table Mountain Group, South Africa) (Hay and Hartnady et al. 2001; Weaver et al. 2002; Blake et al. 2010).


Industries that abstract from aquifers include industrial agriculture, mining, geothermal energy and ground-source heat pumps, disposal and/or storage of hazardous wastes (e.g. landfills, nuclear waste), fluid injection (e.g. oil and gas extraction through hydraulic fracturing or ‘fracking’ and associated wastewater reinjection), and underground construction activities. Such pressures are leading inexorably to stronger competition/interactions between the different industries, with sometimes unforeseen consequences.


© Shutterstock/Eric Buermeyer


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