The world’s freshwater availability is highly problematic, with only 3% of earth’s water being fresh, and 2.6% of that being locked away in glaciers and polar ice caps [1]. This freshwater availability ‘curse’ often provides the foundations for water crises to occur when a shortage of freshwater resources fails to meet the demand. Water crises can be seen across the planet, with 4 billion people living in water scarcity as sustainable water management becomes an increasingly complex challenge. Climate change and meteorological (weather) conditions have a fundamental role to play in water crises and are often major underlying drivers [2, 3].
Regions that experience water crises are likely to have underlying meteorological conditions that promote a reduced water supply. For example, in northwest India, there is high intra- annual rainfall variability, whereby 50% of the region’s rainfall falls in 15 days [4]. This results in a hotspot of groundwater depletion, with groundwater storage declining at a rate of 2cm/year [5, 6]. The impacts of meteorological conditions have also been seen in Sao Paulo, Brazil, where they acted as a key driver of the 2013-2015 water crisis. During this 2-year period there was approximately a 50% decline in annual rainfall levels as a result of the main rainfall mechanism not occurring in the region during the 2014 summer months [7, 8]. It is suggested that this freak meteorological condition stopped clouds from forming and created a drought which saw water inflows to reservoirs fall 70% below the historical mean [9].
These meteorological conditions have been and will further be impacted by climate change. In the Arab region, 60 million people have been affected by climate-related drought from 1970-2019 [10]. Meanwhile, the 21st Century Colorado River hot drought from 2000-2014, which saw annual Colorado river flows drop by 19% from the historical average, was partly due to unprecedented temperatures (0.98°C above the historical average) [11]. Furthermore, it is suggested that continued business-as-usual warming is likely to reduce flows in the Colorado by 35% by 2100 [11]. In Sao Paulo, projected climate changes suggest that there will be an increased risk of droughts in the future, with the RCP4.5 and RCP8.5 IPCC scenarios indicating a 2-month extension of the hydrological dry season and a 35% decline in streamflow during this extended period [12]. Moreover, CMIP6 climate model simulations show that in South Africa’s Western Cape the likelihood of a multiyear drought, as seen in the region during the period of 2015-2019, is double as likely in the future as a result of anthropogenic greenhouse gas forcings [13]. These examples serve to highlight that climate change acts to strengthen meteorological conditions in a wide range of locations.
Ultimately, as the impacts of climate change increase through increasing global temperatures, the role of climate change in causing water crises is likely to rise significantly. Especially in the future as climate change further accentuates weather extremes and adverse meteorological conditions.
There are also a number of other major drivers of water crises, including human pressures and poor or lack of governance.
Increasing human pressures, through growing populations and demand, as well as through poor agricultural practices, can put significant amounts of pressure on regional water resources. In the Nile Basin, some of the highest levels of human pressures on water sources in the world are seen. The Basin is shared by 11 countries, with the majority of economies depending largely on the agricultural industry and therefore the Nile to support them [14]. For example, Egypt depends on the Nile for 97% of its irrigation and drinking water [15]. Currently, the Basin supports countries with a total population of 490 million people, and this is projected to double by 2050, approaching one billion [16]. Along with a number of other drivers, this human pressure has resulted in almost half of the countries being projected to live below the water scarcity level of 1000 m3/person/year by 2030 [14].
Governance crises can also often go hand-in-hand with water crises. For example, Sao Paulo has historically experienced poor governance and during the 2013-15 drought period, which exacerbated the effects of the water crisis. Historic poor management of water in the city included changes to conservation laws that reduced the protection of the watershed and failure to control pollution from industry. This meant that the region was unprepared for dealing with a water crisis.
Ultimately, meteorological conditions and climate change play a significant role in facilitating water crises. Importantly, however, water crises are often not a result of just one key driver, but instead tend to be driven by a culmination of factors that exacerbate each other. It is important to understand the complex drivers at play, as well as their interactions between each other, in order to help manage water resources in sustainable and fair ways. If effective and location-specific water management is not adopted on a global scale, then we are likely to see future water crises play out in ways that result in conflict and may even lead to ‘water wars’ [17].
[1] Hall, J.W. et al. (2014) Water Security: Coping with the curse of freshwater variability. Science, 346(6208): 429-430.
[2] Doeffinger, T. and Hall, J.W. (2020) Water stress and productivity: an empirical analysis of trends and drivers. Water Resources Research, 56(3), p.e2019WR025925.
[3] Mekonnen, M.M. and Hoekstra, A.Y. (2016) Four billion people facing severe water scarcity. Science advances, 2(2), p.e1500323.
[4] Devanand, A. et al. (2019) Choice of irrigation water management practice affects indian summer monsoon rainfall and its extremes. Geophysical Research Letters, 46(15), pp.9126-9135.
[5] Rodell, M. et al. (2018) Emerging trends in global freshwater availability. Nature, 557, 651–659.
[6] Asoka, A., et al. (2017) Relative contribution of monsoon precipitation and pumping to changes in groundwater storage in India. Nature Geoscience, 10(2), pp.109-117.
[7] Braga, B. and Kelman, J. (2016) Facing the challenge of extreme climate: the case of Metropolitan São Paulo. Water Policy, 18(S2), pp.52-69.
[8] Otto, F. et al. (2015) Factors other than climate change, main drivers of 2014/15 water shortage in southeast Brazil [in “Explaining Extremes of 2014 from a Climate Perspective”]. Bull. Amer. Meteor. Soc., 96 (12), S5–S9.
[9] Milano, M. et al. (2018) Water supply basins of São Paulo metropolitan region: hydro-climatic characteristics of the 2013–2015 water crisis. Water, 10(11), p.1517.
[10] Borgomeo, E. (2020) Tackling the trickle: Ensuring sustainable water management in the Arab region. Earth’s Future, 8(5), p.e.2020EF001495.
[11] Udall, B., & Overpeck, J. (2017) The twenty-first century Colorado River hot drought and implications for the future. Water Resources Research, 53(3), 2404-2418.
[12] Gesualdo, G.C. (2019) Assessing water security in the São Paulo metropolitan region under projected climate change. Hydrology and Earth System Sciences, 23(12), pp.4955-4968.
[13] Kam, J. et al. (2021) CMIP6 model-based assessment of anthropogenic influence on the long sustained Western Cape drought over 2015-19 [in “Explaining Extremes of 2019 from a Climate Perspective”]. Bull. Amer. Meteor. Soc., 102 (1), S59–S66.
[14] Siam, M. S., & Eltahir, E. A. B. (2017). Climate change enhances interannual variability of the Nile river flow. Nature Climate Change, 7, 350.
[15] Wheeler, K.G. et al. (2020) Understanding and managing new risks on the Nile with the Grand Ethiopian Renaissance Dam. Nature communications, 11(1), pp.1-9.
[16] UNEP (2013) Adaptation to Climate-change Induced Water Stress in the Nile Basin: A Vulnerability Assessment Report. Division of Early Warning and Assessment (DEWA). United Nations Environment Programme (UNEP). Nairobi, Kenya.
[17] Swain (2001) Water wars: fact or fiction? Futures, 33(8-9), pp.769-781.
Abi Jones 