4. Africa Needs Irrigation... particularly on small rural farms!

What is irrigation?

Irrigation is the artificial application of water to the land or soil.

Fig. 1 A classic overhead sprinkler irrigation system, common on many farms today (Source: ULS group)

When did it begin?

It an ancient technique which began around the same time as agriculture, ~ 11,000 years ago. It was the first major human modification of the natural hydrological cycle.

Why is it important?

It enabled societies to reduce their dependency upon the timing and volume of rainfall: extending and increasing the reliability of the growing season. As a global average, irrigated land produces crop yields that are almost FOUR TIMES HIGHER than unirrigated land! (FAO AQUASTAT). In fact, Wittfogel (1957) claimed that irrigation schemes were so crucial to the rise of many great civilizations, such as Ancient Egypt, that they should be referred to as “hydraulic civilizations" (Butzer, 1976).

Fig. 2 Depiction of farming life in Ancient Egypt, clearly showing the irrigation channels that were so fundamental to its development as a ‘hydraulic civilization’

Why does Africa need irrigation?
My last post highlighted that rainfall in most of Africa is hugely variable and that this variability is expected to increase due to climate change (Niang et al 2014). Therefore, rain-fed agriculture is risky and going to get riskier. Furthermore, Africa has one of the fastest growing populations in the world, meaning food demand is rapidly increasing. Irrigation increases both agricultural reliability and productivity. Clearly it is an important strategy for farms in Africa now and into the future.

What's the current extent of irrigation in Africa?

Despite the obvious benefits of irrigation, only 5% of agricultural land in Africa is currently 'equipped for irrigation' (which is generally regarded as a good proxy for the total area actually irrigated), the remaining 95% is rain-fed. Whereas in Asia, 37% of agricultural land is 'equipped for irrigation' (Siebert et al., 2010). Clearly, Africa has a lot of work to do! However, Vilholth (2013) highlights that small-scale irrigation in SSA is hard to quantify and therefore Africa’s ‘5%’ figure may be an underestimate. Nevertheless, the map below shows the 2013 estimation of the global distribution of areas equipped for irrigation in percentage of land area. The land area is divided into a grid of cells, roughly 1km x 1km in size (… not exactly because they are measured in decimal degrees, which account for the curvature of the earth, and not in meters) and the percentage coverage in that cell recorded. For the majority of countries the base year of statistics is in the period 2000 – 2008 (Siebert et al., 2013). From this map you can clearly see the concentration of irrigation in Asia and the lack of it in Africa!

Fig. 3 The map shows area equipped for irrigation in percentage of cell area (cell size = 5 minutes or 0.083333 decimal degrees). For the majority of countries the base year of statistics is in the period 2000 - 2008. (Source: Siebert et al., 2013) 

  
Rural small-scale farms:
As of 2010, the FAO reported that over half of the sub-Saharan workforce was employed in agriculture and the majority of these worked on small-scale rural farms of ~1-5ha (Gollin, 2014). Promoting expensive, centralized irrigation techniques that are only feasible on a large scale is unlikely to help expand irrigation on these small rural farms. Therefore, my next few posts will investigate how we can increase the extent of irrigated agriculture in Africa (particularly SSA), via relatively cheap, small-scale techniques to improve groundwater access and increase rainwater storage.