Climate Change and Water Availability

Today's post is focused on the theme of water availability, and more precisely, how climate change will likely affect it.

To begin, let's define water availability as the amount of water a country or region has, for use (domestic, agricultural and industrial). This is related to water scarcity, and the Falkenmark Water Stress Index stipulates that when a country falls below 1000 m3 of freshwater per person per year it experiences water scarcity and below 500 m3, absolute scarcity. Climate change and many other factors can influence whether a country experiences water scarcity, as the ability of its population to access and use water is dependent (at least in part) on its physical water resources.

So how do changes in climate affect the real availability of water?

Kusangaya et al. (2013) reviewed the many potential impacts of climate change on water resources in southern Africa, encompassing both physical and human consequences. There is a general consensus that increasing atmospheric greenhouse gases as a result of human activity will have widespread effects on the environment, mostly due to increased temperatures. For example, climate change is likely to cause an increased frequency of occurrence of extreme events such as droughts and intense storms. Temperature rises can also intensify the hydrological cycle (as I mentioned in my last blog post!) and may lead to increased evaporation but also increased rainfall. However, it is important to note that regional patterns differ from global patterns, so areas that experience a greater increase in evaporation, relative to increase in rainfall, would experience a real loss in available water. In Matondo et al. (2004), they claim the UN Environmental Programme study in 1989 predicts that greenhouse gases will elevate average precipitation by 5–15% and evapotranspiration by 10–20%; hence, real water available will decrease. Kusangaya et al. focused on southern Africa, and emphasise that southern Africa is likely to experience significant temperature rises, with more rapid increases in maximum temperature than minimum temperature extremes. At the same time, dry periods in southern Africa have become longer and more intense.

There is little consensus on the prediction of rainfall in Africa under different climate projections, but even if rainfall increases in some regions, with (much more certain) projections for population growth showing alarming rates of growth that are distributed unevenly, it is likely that real availability and access to water will fall. Population growth, particularly in urban areas, can put immense amounts of pressure on water resources. For this reason, many studies such as Carter and Parker (2009) stress that urban population growth, and consequent rise in food and fresh water demand and energy costs, are likely to be much more important than the physical impacts of climate change.

In summary, the two main physical areas that can affect water availability due to climate change are temperature and rainfall, which are also interlinked. It is difficult to accurately predict these changes because of this feedback loop, and particularly as rainfall is characterised by high inter-annual variability. On top of this, human changes (perhaps due to climate change, perhaps not) can contribute to changing water availability.

There are already real problems with water availability and access in Africa. UN Water estimates that 85% of the world population lives in the driest half of Earth, and with water availability estimated to decrease in many regions. This, in conjunction with population growth and growth in demand for water and food, represents a potentially deadly situation unless water management and adaptation strategies can mitigate the physical differences in water available to supply and water demanded.

Although climate change presents real concern for the physical availability of water, Mukheibir (2010) states that "the scarcity referred to globally is mostly rooted in power, poverty and inequality and not in the physical availability". UN Water echo this sentiment as they state that "water scarcity is both a natural and a human-made phenomenon. There is enough freshwater on the planet for seven billion people but it is distributed unevenly and too much of it is wasted, polluted and unsustainably managed". And while there is a lot of emphasis on cooperation around water (from the UN Sustainable Development Goals to scientific articles) to help solve the pressing issue of improving water access in a changing climate, more needs to be done to create optimistic scenarios for humans despite dire environmental changes.