Is Groundwater The Way Forward?

(Source: scidev.net)

“Irrigation is the most important water use sector accounting for about 70% of the global fresh water withdrawals” (Dey et al., 2017). It is commonly believed that irrigation is carried out frequently by farmers across the world as a means to water their crops, but this is not the case for farmers in Africa. It is estimated that of all the arable land in Africa, only 6% (around 13 million ha) is irrigated (Agra, 2019). To put this into context, 36.8% of India’s arable land is irrigated (World Bank). This blog post will explore Sub-Saharan Africa’s (SSA) groundwater usage and the future of groundwater in SSA.

There are two main sources of water for irrigation. The first is surface water, which is the most common water source for irrigation in Africa. "Surface water is water that is found on the Earth’s surface, such as water in rivers, lakes and oceans" (National Geographic, n/d). The second water source is groundwater. "Groundwater is water that has travelled down from the soil surface and collected in the spaces between sediments and the cracks within rock" (National Geographic, n/d). It is often the ‘backup’ method for farmers during droughts and periods of low rainfall (Giordano, 2005). Figure 1 shows the distribution of groundwater resources in the world, with levels in SSA ranging from medium to very high and areas with local and shallow aquifers.

Figure 1: Groundwater resources of the world

(Source: whymap.org)

The potential for groundwater use is extensive as it is the largest stock of freshwater in Africa. Despite this, only 7 of the 43 countries in Sub-Saharan Africa (SSA) use more than 10% of their groundwater supplies. A reason for this is that groundwater knowledge and management is lacking (Cobbing, 2019). Without the knowledge required to pinpoint the locations of groundwater, it is difficult to extract groundwater efficiently and effectively. The majority of small-holder farmers draw water from shallow groundwater sources for small-scale irrigation but this is not sustainable as shallow resources are more likely to run out faster. Rather than over abstraction being the main issue with groundwater in SSA, the issue of underdevelopment poses a problem to small-holder farmers.

Groundwater has the potential to double small-holder farmers’ yield, where they will benefit greatly if they use it to irrigate cash crops (Karlberg, 2004). Motor pumps are one of the most efficient ways of extracting deeper sources of groundwater. Farmers will produce higher yields, in comparison to irrigating 1000 m² in 9 hours, and be more time effective than when using buckets or watering cans (de Fraiture, 2013). Small-holder farmers can become more self-reliant through small-private irrigation without having to rely on rainfall which is highly unreliable. By using motor pumps, rural electrification will also be encouraged, leading to an improvement in the livelihoods of rural farmers in SSA.

However, there are costs and limits to groundwater irrigation. Over-extraction of groundwater can lead to depletion and even when extraction is ‘sustainable’, replenishment rates may fall well behind. For the poorest farmers, the cost of a motor pump may hinder them as they are often expensive. Although subsidies are offered for motor pumps, it causes farmers to be more reliant on them and often misrepresents the market (Villholth, 2013). Furthermore, motor pumps require diesel to run and increasing diesel prices may have an even bigger impact on small-holder farmers as their profit margins become restricted and are dependent on fuel prices. The environmental impacts of using motor pumps are clear – diesel fuel is required and chemicals used for agriculture may end up polluting surface water, causing harm to species and locals who use it as their source of drinking water.

For small-holder farmers in SSA, irrigation via groundwater is essential. In a project funded by the EU in Zimbabwe, farmers achieved an income increase of 265% through higher yields due to constant groundwater supplies (Villholth, 2013). This goes to show that groundwater irrigation can have a positive impact on small-holder farmers. A push is needed towards the promotion of groundwater irrigation in SSA through educating farmers and reducing the cost of motor pumps so they can be affordable for all to use. But in order for farmers to gain more reliable irrigation methods, surely it does not have to come at the expense of the environment.