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.

The Changing Water Cycle

As I spent this week thinking about what to write for this blog on water and environmental change, I started to realise just how much the two topics can cover. I mentioned this in my previous post but have started gaining a better appreciation for what that really means. I'm therefore going to pick out some themes I find interesting and write each blog post on such a theme, hopefully linking them with other blog posts and other blogs as I go. So for this blog, my theme is going to be the changing water cycle.

The environment is always changing; that much scientists know to be true. An integral part of the environment is the water cycle, and as the environment changes, so does the water cycle. I think it's important to say that the water cycle is changing due to changes in climate, but that the climate is also changing due to changes in the water cycle. It's a never-ending cycle and no one really knows where it began. So in this blog post, I'm just going to give a bit of context into why changes to the water cycle matter and what kind of changes can and have occurred.

Why does the water cycle matter?
Wikipedia defines the water cycle, or hydrologic cycle, as "the continuous movement of water on, above and below the the surface of the Earth". It also specifies that the water cycle involves exchanges of energy, which leads to temperature changes and therefore, influences climate. As you can imagine, this has implications for numerous areas of importance. Stocker and Raible (2005) stipulate that water has "profound effects on our planet's climate", from influencing the greenhouse effect through water vapour to ocean currents dictating regional climate patterns. This is reflected in the many processes that rely on water, not to mention the effects water has on human activity.

Put simply, natural processes rely on water and human processes rely on water. The water cycle controls the distribution of water, including where water is distributed, what state water is stored in (solid, liquid or gas), how often precipitation occurs, and how water moves around the world. For humans, understanding how the water cycle works is imperative for water management. For example, with changes to precipitation, water availability changes and mitigation techniques put into place to best use the water that is available. Arnell (1999) claims that precipitation will increase, but increase unevenly around the world, with large parts of land surface experiencing a reduction in precipitation. Using models, Arnell states that climate change will increase the number of countries under water resources stress by 2025. Clearly, changes to the water cycle matter to many different aspects of the natural and human environment.

What kind of changes have occurred?
The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report working group report 'The Physical Science Basis' (2013) states that there is strong evidence for changes in the water cycle due to climate change. Observations since 1970s show increases in surface and lower atmospheric water vapour, shifts in ocean salinity due to the addition or removal of freshwater, changes in precipitation over land and an increased occurrence of extreme rainfall events. The report emphasises that ocean salinity is an effective way of measuring changes to the water cycle as it "naturally reflects and smoothes out the difference between water gain by the ocean from precipitation, and water lost by the ocean through evaporation". Durack et al. (2012) also use ocean salinity as a measure of the water cycle, and their study provides evidence that the water cycle has intensified since 1950. They also suggest that substantial intensification (16-24%) of the global water cycle will occur in a 2° to 3° warmer world.

I hope this brief introduction to the water cycle gives some context to what I'll be looking to blog about; including many more specific studies, with a focus on Africa. An area I'd like to explore further is anthropogenic effects on the water cycle and climate. The water cycle affects climate and climate in turn affects the water cycle. This is a mechanism as old as the Earth, and I'm interested in whether humans are negatively modifying this mechanism. For example, the proposed Anthropocene epoch (coined by Crutzen and Stoermer 2000) suggests that humans are preventing the natural glacial cycles of Earth through continued warming. The warming climate invariably has an impact on the water cycle; thus, humans could be seen as interfering with this natural occurrence.

Thanks for reading!

Introduction

Let me start by saying one of the best and simultaneously one of the worst things about studying geography is that it encompasses everything. It means there are no clear boundaries to where your area of interest ends, and a geographer could spend eternity learning. However, it also means there are relevant links to any topic, and consequences of one area can be felt in many areas. This is exactly what I'm aiming to explore in this blog. For my module this term, GEOG3038 or Water and Development in Africa, I'll be looking at how water and environmental change (climate change, land use change etc.) are linked and how they can affect one another.

It's easy for climate change doomsayers to harp on about how, with a changing environment, everything we know will worsen the propensity for humans to survive and thrive on Earth and ultimately lead to the demise of mankind. However, I'm more interested in investigating the real complex dynamics of the physical environment and the use of water by humans, from water management in the face of temperature increases to technological solutions to changing water sources and much much more.

While looking at water and environmental change could be seen as purely physical in nature, I believe that water in today's world is inherently related to both physical and socio-economic factors. There are many contributing factors to how we use water, from physical water availability to political and social barriers to access. Therefore I'll be using this blog to discover the many different complex links between changes to environment and water use.

I hope this gives you a bit of context on what this blog will cover and I'll be posting again soon with my first official blog post that will begin to delve into this topic.