Water water everywhere... But not a drop to drink!

Water Variability... The factors behinds it.

Last week we figured out that Africa actually has enough water available, and cannot be considered water scarce. But it's the variability of water throughout the season and between regions that present us with the challenge of managing African water reserves. Today I will be discussing the natural/ physical drivers of water resources in Africa by focusing on two key articles presented by Conway et al 2009 and Taylor (2004).

Physical Setting 

An important element of East and South Africa is that it lies on an altitude of around 1000 meters above sea level, compared to 400-600 meters in North/ West Africa. This formation of the East African Rift System due to swelling of the Earth's crust in the Oligocene eras has a predominant effect on climate and rainfall distribution. The mountain uplift creates a rain shadow effect that reduces moisture availability on the Rift Valley mountain side, producing strong aridification (Maslin 2014)

Tectonics also largely characterize patterns of surface drainage. Large lakes have formed in troughs throughout the East African Rift Valley. Warping of the land surface has also created surface flows I.e.  Lake Victoria and Kyoga, as well as being a major determinant in the formation of river basins (up warping of the rift  on the western side of Lake Albert divides the basins of the River Nile and River Congo). 

Climatic Setting 
Seasonal climate in Africa is controlled by global atmospheric circulation trends. Atmospheric circulation forms as a result of unequal heating of the Earth's surface. At the equator heated air expands, rises and moves towards the pole regions, where it then cools and sinks at approximately 30 degrees North and South, A fraction of it returns back to low latitudes thus completing a cycle, known as a Hadley Cycle. The area near the equator where the moisture rich flows meet is the Inter Tropical Convergence Zone (ITCZ). The ITCZ is not static but moves as a result of changes in solar radiation, which is the main driver of seasonal rainfall variability across much of Africa.

Figure 1 below illustrates the movement of the ITCZ across Africa between January and August. In December the ITCZ reaches the southernmost latitudes, where it brings moisture to before moving north and bringing heavy rainfall to northern latitudes up to July. This annual cycle creates a uni modal distribution of rainfall for countries in South and North Africa. However places near the equator at lower latitudes have a bimodal rainfall cycle, as the ITCZ passes twice throughout the year. Thus as Taylor (2004) correctly noted, this means that regions at the periphery of the ITCZ receive comparatively little rainfall i.e.  Namib Desert in Northern Africa, compared to those at latitudes of 10 degrees N/S.

 Figure 1: Movement of ITCZ across Africa (Ziegler et al 2013)

This has profound impacts on water use due to the high seasonal water variations. Regions are having to adapt their water use depending on the season, in sectors like agriculture which heavily depends on rain for irrigation especially for small hold farmers, their planting seasons take into consideration this rainfall variability , timing it to the arrival of water. 

As we can see water in Africa comes with a large uncertainty and variability, which presents a challenge to adapting to these unreliable water sources. I think concerns over irrigation should address these issues and present a sustainable solution that can tackle large variability of rainfall as well as looking at other sources.

Water Scarcity

Does Africa have enough water?

In today's post I will review Falkenmark's indicator  used to measure water availability, to figure out if Africa actually has enough water resources to meet its demand, by predominantly focusing on a paper by Chenoweth 2008. 

  http://dx.doi.org/10.1080/02508060801927994 

Water is essential to provide for the basic needs and development of any nation. The extent to which its people can thrive, almost always depends on fresh water availability, which is necessary for sanitation and the production of food. However in recent years, rising populations, particularly in Sub-Saharan Africa, mean that nations aren't able to satisfy their water needs.

Indicators of  water scarcity are increasingly used to measure the extent to which societies are able to meet their basic water requirements and whether policy needs to address this issue. In his assessment of national water scarcity indicators, Chenoweth  2008 reviews the effectiveness of popular water scarcity indicators at measuring ability to satisfy water demands. 

The most standard indicator of water scarcity is one proposed by Falkenmark (1986), based upon water resources per capita. Thus a country faces:

• Relatively Sufficiency : >1700 cubic metres of water per capita/ year

• Water Stress : < 1700 cubic metres of water per capita/year

• Water Scarcity (threatening economic development and health): <1000 cubic metres of water per capita/year.

• Absolute Water Scarcity: <500 cubic metres per capita/year.

However, as pointed out by Chenoweth, this indicator has major limitations, as it doesn't account for differences in water use trends between countries ( Ruskin et al 1997). Moreover it is hard to tell how much of this water goes for domestic / agricultural/ industrial uses and the equality of water distribution between people, since it is measured as per capita water availability. 

As mentioned further in the article, the indicator does not consider the fact that countries are able to adapt to water scarcity and reduced availability. Allan (2001) suggests, that countries have learnt to adapt to reduced water resources by compensating it for grain imports, thus diminishing (to an extent) the link between water availability and food security. 

Data suggests that Africa overall has about 9% of world's water resources and 11% of the global population (FAO 2003), and hence despite common misconceptions it cannot be considered as water scarce. Average water availability is 5720 cubic metres per person/year (Shiklomanov 1999) so Africa can in no way be considered water scarce. What matters however... is accessibility to these water reserves. It's no use having the water there if you cannot access it. There is also a large discrepancy between regions within Africa in terms of water resource accessibility driven by a range of physical and human factors, something we will focus on in the next blogpost...

But for now... we have concluded that Africa actually has enough water resources to sustain itself. What's important is whether there are opportunities for accessing those water reserves? Furthermore, I would agree with Chenoweth, that whilst the Falkenmark Water Stress Index provides a useful insight into water resource availability per person, its implications mean that it is not particularly useful in addressing the problem and demystifying the actual situation with current water issues.

Food for thought...

New post coming shortly!

A Continent Under Threat

Exploring Agricultural Water Use in Africa. 
Introduction.

Food security is a global issue today, particularly in countries where limited resources are finding it hard to meet the demands from rapidly growing populations. In this blog I want to explore the issue of water use for agriculture in Africa, where water scarcity is threatening food production.



Agriculture accounts for 70% of world's total water use. Think for yourself, a whole 850 liters of water per capita per day is required to produce the average person's daily food intake (Inocencio, Sally and Merrey, 2003). With rising populations ( population of Sub- Saharan Sfrica predicted to reach 1 billion by 2025) agricultural production must also increase to sustain the hungry people.


So in a sense it all comes down to water. To be able to feed its rising population and lift themselves out of poverty, Africa needs a reliable access and an efficient use of water for agricultural needs. But how can we achieve that?

In this blog I will discuss the issue of scarce water resources for agricultural production and whether there is an adequate solution to resolving the water crisis in relation to food security. In the following posts I will address these issues:

1. Water Scarcity and Water Stress Indicators: Does Africa have enough water?
2. Causes of Water Crisis in Africa
3. Effects and implications for food security
4. Improving agricultural water use efficiency

Keep reading my blog and check for weekly updates. I will be posting shortly :)