Water resources have many different purposes. Taylor (2004) identifies 3 main uses in Africa:
Domestic uses- 13% of total use
This includes household needs such as drinking, cooking, washing, as well as municipal and commercial activities.
However
rapid urbanisation due to population growth and rural- urban population, has
meant that many urban and piped supplies have been overwhelmed, especially in
East and Southern Africa.
Agricultural uses- 83% of total use
This refers to both irrigation and cropland and watering of livestock.
Due to strong seasonality in river flow, particularly at high latitudes in Southern Africa, large dams are often constructed to store peak flows during the dry season.
Agricultural uses make up a staggering 83% of total water use. This is both commercial and traditional/ communal.
Industrial uses- 4% of total use
In East and Southern Africa this is dominated by the mining industry. This is reflected in the proportion of water used for industry (>10%) by countries such as Botswana, Democratic republic of Congo, Angola, and South Africa.
Large increases are expected in HEP generation in Southern Africa due to both rising demand and the high potential for HEP generation.
Climate change
Climate Change has the potential to impose additional pressures on water availability and demand in Africa, many of which they are already currently facing. Water Supply Security, Food security and Energy security are at increasing risk, with growing demands due to population growth and urbanisation. Climate change is set to rapidly increase the magnitude of these problems.
Below is a summary of the projected impacts of climate change in Africa:
Figure 1: Summery of the projected impacts of climate change in Africa, taken from the Report Summary for Policy Makers, IPCC, 2007
Africa is extremely vulnerable to these changes, however, the impact across the continent is not uniform. Therefore, from this point onwards I will be focusing on East Africa.
Next week's blog will focus on East Africa, providing a broad overview of the region. The following week will then look at the production of maize, focusing in on Tanzania.
Africa is bigger than China, India, Europe and the United States combined (figure 1). The standard Mercator projection (the map that we are used to seeing) of the world massively underestimates the true size of Africa. The African continent, with a land area of nearly 30 million km2, holds a wealth of natural resources including minerals, forests, wildlife, and a rich biological diversity. It also has some of the driest deserts, largest tropical rainforests and highest equatorial mountains in the world. Key natural resources are however unevenly distributed (Urama, 2010).
Rainfall variability
Rainfall in Africa displays high levels of variability across a range of spatial and temporal scales. Annual rainfall is estimated to be 20360 km3. The central region of Africa, which covers approximately 20% of the total land area, receives 37% of all precipitation. Conversely, the northern region which has a similar area receives less than 3% of the total precipitation (UNECA, 2011).
Figure 2: Average annual rainfall and Variability in annual rainfall
Note rainfall variability is represented by the coefficient of variability (CV), calculated as the standard deviation devised by the mean annual rainfall. It is expressed as a percentage and indicates how much rainfall varies from average annual rainfall.
Figure 2 shows how rainfall in Africa varies within and between regions, dependent on latitude, topography, seasons, continentality, and global climate circulations (which I will go on to talk about). Map 1 shows that rainfall tends to decrease away from the equator, and is scarce in the Sahara, Eastern Somalia, and South Africa. Rainfall is most abundant in parts of the highlands of Eastern Africa, large areas of the Congo Basin, central Africa and parts of coastal West Africa. Map 2 shows that most of Northern Africa experiences highly variable rainfall. Variation is the measure of how much rainfall varies from the annual average- This regions variation coefficient is > 45%. Comparable to the Congo Basin which is much less variable, with a variation of ~10%. Much of the continent has a variability coefficient of ~15-35%.
The inter-tropical Convergence Zone (ITCZ)
The ITCZ is the convergence of 2 'Hadley Cells' where warmer air rises, cools, sheds precipitation, moves poleward and descends delivering little precipitation (See video 1 for more information).
Video 1: The inter-tropical convergence Zone (ITCZ)
The ITCZ is arguably the most important control over the spatial and temporal variability in rainfall. The many different features of atmospheric circulation (which control the ITCZ) drives the seasonal development of the tropical rainfall belt over Africa. The ITCZ moves North and South throughout the year in response to solar radiation: the northern hemisphere have their rainy season in July when solar radiation is at its peak (summer) and the Southern Hemisphere have their rainy season in January (Taylor, 2004). The movement of the ITCZ across Africa means that the northernmost and southernmost latitudes only have one annual wet season, whereas the regions between these latitudes have 2 (figure 3).
Figure 3: Modern rainfall variability over Africa
(a) January and (b) August. Colours indicate days per month with measurable rainfall. The climate over large parts of Africa is characterised by a strong seasonality with summer monsoonal rainfall and the approximate position of the ITCZ (red band) migrating between the north and south of the continent over the course of the year
As mentioned before, it is not only global climate circulation that drives African climate, and therefore rainfall variations. It is several processes that are interrelated in complex ways and is still not yet fully understood yet (Conway, 2009).
Change in Rainfall variability
In the C20th there has been observed warming in Africa, especially since the late 1960s. This has occurred at a rate of about 0.5 ℃ per decade, however this increased in the last 3 decades of the century. This trend is not consistent over the whole continent. In coastal and major inland lakes of East Africa decreasing trends in temperature were observed.
For most of Africa there has been either a decline or no long-term trend in annual rainfall, an increase in inter-annual variability has however been observed. From the early 1970s there has been reports of 'drying' in the Sahel region. However, parts of East Africa showed a mean linear increase in annual rainfall of ~10-20% from 1901 to 1995, which is part of a wetting trend seen across equatorial Africa (UNECA, 2011). Both trends have been linked with El Nino- Southern Oscillation (ENSO).
The most significant change recorded has been a long- term reduction of rainfall in the semi-arid regions of West Africa and the Sahel.
The importance of Rainfall Variation
Throughout Africa, this variability brings significant implications for society.
Where most agriculture is rain-fed, crop growth is limited by water availability- rainfall variability during a growing season generally translates into variability in crop production.
There are many examples of the challenges posed on Africa due to the large variability in water supplies including: Lake Chad fisheries; balancing supply and demand on the Nile for Egypt; Irrigation management in the Greater Ruaha River in Tanzania. The main driver of much of the variability in river flows is rainfall (Conway, 2009). A 10% drop in precipitation reduces river discharge by 17- 50% (De Wit, 2006).
Climate Change
As the impacts of anthropogenic climate change begin to manifest and we see a shift in flows and variability across Africa (figure 4), we need to have a better understanding of the drivers of rainfall variability and rain-fall runoff interactions.
Climate change has the potential to impose additional pressures on water availability and demand in Africa. Next weeks post will focus on how climate change will impact water resources in Africa.
Hi World and welcome to my new blog ' Water in a Changing World- What does this mean for Africa?'
This is my first time ever blogging, quite exciting really! This blog is part of my 3rd year Geography module 'Water and Development in Africa'. My blog will be exploring the complex relationship between Environmental change and Water in Africa, using a range of academic reports, news articles, books and videos. An array of topics will be covered, not only focussing on climate change, but also land use changes, and the impacts on water supply and quality, and the further implications this has for Africa, and their future.
The importance of water
Freshwater resources make up only a small fraction of water on the planet. While nearly 70% of the world is covered by water, only 2.5% of all the water on earth is freshwater. Even then <1% of this freshwater is easily accessible, with much of it trapped in glaciers and snowfields (Figure 1).
Water is a resource we often take for granted, especially living in the UK- London, having access to clean, running water, by the turn of a tap. It is a fundamental necessity; however, we can often forget that this is not the case for everyone around the world. Due to Geography, climate, engineering, regulation and competition for resources, some regions have an abundance of freshwater, while others experience drought, and access to minimal or no safe water supplies. The Increasing concern now is that the combination of Climate Change and a rapidly growing demand will magnify those extremes, and further threaten water supply.
Climate change and water
Climate change is causing global increases in temperature on Earth. The mean annual temperature rise is likely to reach 2 ℃ by 2100 (Niang, 2014). Increasing temperatures of > 2 ℃ will have serious consequences including an increase in the number of extreme events. When most people think of the water crisis, they often think of years- long droughts or dry monsoon seasons. However, a further consequence is intensification of precipitation, with fewer, low and medium intensity precipitation events and more heavy precipitation events. This is because as temperatures increase, the holding capacity of water in the atmosphere will increase, leading to less frequent but more intense rainfall events (Owor et al, 2009).
While there is no way to predict exactly what the worlds water resources will look like in the future. It is projected that water stress- the measure of supply, relative to demand- will likely increase rapidly across the globe, as more people compete for fewer and limited supplies of surface-water.
Figure 2: Projected 2040 global water stress by country
It is the most ethnically diverse region in the world.
Most countries in Sub-Saharan Africa are classified as 'Developing' countries; whereby in strict economic terms, is one of the poorest regions in the world.
It is home to the highest rates of population growth.
It is the most rapidly urbanising region in the world and presently the most rural.
There are several reasons why poverty has become an epidemic in Africa: arguably the lack of access to clean drinking water is one of the greatest and often overlooked causes. The lack of water is an often-immeasurable obstacle, that has trapped many in the cycle of poverty.
Substantial increases in freshwater withdrawals and consumption is projected for the future of SSA. Therefore, with the growing concern of future water resources, this blog will explore what this means for the rapidly changing continent of Africa.
Feel free to comment on my posts, and I look forward to learning about this ever complex issue, in this module in the coming months and hopefully beyond.
