Re-evaluating Africa's Reliance on Rainwater

I hope that my last post provided an insight in to the complex nature of Africa’s food insecurity.  The post highlighted that achieving food security in Africa will require changes across many sectors and coordination between these sectors. To achieve food security (as well as increased agricultural productivity, economic development and sustaining an increasing population) a foundation of the ability to access and utilise reliable water sources will also be essential.

The physical landscape plays a very significant role in determining the climate of an area, and the African land mass is no exception. A low-pressure area called the Inter-Tropical Convergence Zone (ITCZ) lies across the African continent, just north of the geographical equator. The ITCZ is an area of convergence where the moist trade winds meet. Upon meeting, their warm air rises, cools and then sheds its moisture in the form of precipitation. The air, now containing little water, moves poleward and descends providing little precipitation.

The ITCZ creates a latitudinal symmetry of precipitation across Africa; increasing distance from the equator correlates with decreased length, amount and reliability of rainfall. Complicating matters, the rainfall on the continent is highly variable at inter-annual, decadal and longer time scales. This variability has also been exacerbated by climate change and global warming. Therefore, the physical environment plays a large role in determining the geographical distribution of water resources and therefore water scarcity across Africa. Naturally, humans cannot alter the seasonality, variability and locality of precipitation distribution (although, climate change is negatively influencing this), but, what they can influence is how available water is used and managed.  

Annual Average Total Precipitation 1979-2011 (Source: http://www.esrl.noaa.gov/psd/)

The total amount of water available for usage is essentially not going to change and besides Africa has sufficient supplies of water for achieving food security (Africa Water Atlas, 2010). Therefore, the problem is not of quantity but accessibility and distribution (both temporally and spatially). Nevertheless, if food security in Africa is to be achieved, an increase in water supply to the agricultural sector will be crucial. Therefore, efficiency of water use must increase and sustainable management of available water resources must also become paramount.

However, water management is expected to become increasingly challenging because the predicted effects of anthropogenic global warming are yet to be fully realised. Allan and Soden predict that Africa as a continent will warm more than the global mean. Consequently, variability in rainfall and river discharge will increase disproportionately, with weather becoming more extreme and unpredictable (Allan and Soden, 2008). This is also compounded by a predicted increase in the inter-annual variability of rainfall. Therefore, provision of water supplies from precipitation are already and will increasingly become unpredictable and unreliable.

At present, 95% of Sub-Saharan Africa’s agricultural activity relies solely upon rainfall (Africa Water Atlas, 2010). Therefore, the present (and predicted) increase in variability of rainfall, river discharge and water supplies presents a huge barrier to achieving the expected multitude of benefits of investing in the agricultural sector i.e. food security, economic development, reduced poverty rate and reduced urbanization. Essentially, if investment is going to have its intended effects, rainfall cannot be relied upon to provide a reliable water supply to the agricultural sector.

However, this is no reason to lose faith in the possibilities for African agriculture. In fact, there exists sufficient water on the continent of Africa to achieve food security, (Africa Water Atlas, 2010), the challenge is how to exploit such resources. Therefore, a transition away from agriculture’s reliance on rainwater and toward utilising alternative means of acquiring the necessary water is required.

Some possible alternatives to rainwater include:

1)    Construction of dams to create reservoirs for storing water

2)    Rainwater harvesting

3)    Abstraction of Groundwater

4)    Adapting farming practices to work with the new environmental conditions

Naturally, these potential alternatives have advantages, limitations and present new challenges. As well, each option will not be universally appropriate, necessary or indeed possible. Some are also small-scale options whereas others are very much large-scale solutions. There is a clear need to be locally and contextually specific when making decisions on how to manage water. Whilst precipitation and climate become increasingly variable and there persists a need to ensure water and food security, all of the above alternatives will probably form part of Africa’s future. My next post will examine some of the potential alternatives outlined above and investigate how they may form a part of Africa’s ambition to achieve water and food security.

Africa Water Atlas. (2010). 1st ed. Nairobi, Kenya: United Nations Environment Program.

Allan, R. and Soden, B. (2008). Atmospheric Warming and the Amplification of Precipitation Extremes. Science, 321(5895), pp.1481-1484.

BBC.co.uk. (2016). BBC Bitesize - Higher Geography - The cause and impact of the Intertropical Convergence Zone - Revision 1. 

Esrl.noaa.gov. (2016). ECHAM 5 AGCM Simulations Focused on Africa (Climatology and Trends).