Small Scale Groundwater Irrigation

One of the difficulties of quantifying the contribution of groundwater to agricultural production is that a large part of it comes from small-scale irrigation, and thus means the real impact of it is extremely hard to measure. In Ghana, small-scale informal lift irrigation which accounts for 190,000 ha of irrigated land has surpassed large-scale surface irrigation by 7 times (Namara et al 2013.) This obviously means that small-scale groundwater irrigation is making a substantial contribution to the production of food in Sub-Saharan Africa, although official and accurate data is actually lacking.

Smallholders are poorer farmers, generally with landholdings that are smaller than 2 ha, privately owned, and under the complete control of the farmer (Abric et al., 2011). Small-scale irrigation is one of the most expanding types of irrigation, since it is increasingly being promoted by governments and NGO's. Moreover it is deemed to benefit poorer farmers, due to individual uptake modes and operation.

Groundwater irrigation on the whole can be divided into four types, characterised by depth of groundwater source and type of funding. As seen in Table 3 in a paper by Villholth 2013 :

• Type 1:  larger-scale (>100 ha), mechanized, export-oriented crop ie flower farms Ethiopia.
• Type 2:  private development of shallow groundwater by farmers, individually or in small groups, rudimentary wells,  human- or animal-operated mechanical pumps and rope/bucket extraction. Requires low capital investments.
• Type 3: deep-well public systems supported by government, donors or non-governmental organizations (NGOs) for groups of farmers.
• Type 4 :shallow well smallholder schemes subsidized with irrigation structures and input from the public sector, donors and NGOs, such as the fadama systems in Nigeria.

Under this classification system, small scale GWI falls under types 2,3 and 4. 

Groundwater irrigation substantially increases productivity of output, in Ghana , farmers using groundwater had 20% higher net revenues per area irrigated than those using other types of water sources. As discovered by Kamwamba, value added per area of GWI is twice that of other irrigation systems. Despite its obvious advantages, it seems that small scale farmers are not converting rain-fed staple crops to being irrigated, but rather they co-exist and groundwater irrigation supports dry-season crop production ( Shah et al 2013). Hence groundwater irrigation could be a solution to mitigate the effects of drought and natural climate variability.

In his article Villholth then discusses some of the constraints facing small scale groundwater irrigation development by looking at direct and indirect factors.

Pumps- At present small holder GWI done with manual lifting or with small diesel/petrol operated pumps. In Ethiopia, Namara et al (2013) found that 31% of farmers use water lifting devices, of which 84% used buckets and 16% used motor pumps. Motor pumps have a greater water lifting capacity and thus are able to expand the total area irrigated, but have high capital and recurrent costs for maintenance and fuel. Small holders also face long traveling distances to acquire pumps along with high transaction costs.

Wells- can be classified into three types: manual digging, manual drilling and motorised drilling which determine well depth, with costs increasing as you move to using motorised technologies. 

Energy- energy for mechanized pumping comes from fossil fuels or electricity. But this is often constrained by low electrification in rural areas. There is a clear correlation between rural electrification, fuel subsidies and groundwater use.

Markets for produce- for GWI to be profitable it must be used for cash crops which require demand for the crops, well developed road/transport infrastructure and outlets.This is lacking in many rural areas.

These are only some of the factors that the paper discusses which are hindering the development of small scale groundwater irrigation.I think the author largely underestimates the effect of small scale GWI on inequality as being both a cause and effect. Many of the poorer small holder farmers do not have enough capital or finances to be able to afford some of the deeper motorised driling wells or motor pumps which require high capital investments. This means that they are limited to shallow wells using simple technologies such as ropes, which in turn reduces their agricultural output. Whereas those who are richer, substantially benefit from the motorised pumps and have a greater productivity. Essentially small scale GWI causes incomes between farmers to diverge, thereby increasing inequality. I believe this is something that should be taken into account and address if further development of small holder groundwater irrigation takes place.

Another limitation of the paper by Villholth is that it doesn't take into consideration the effect of small holder water irrigation on subsistence farming, which reduces poverty and malnutrition amongst poorer households and has a contribution to overall welfare. 

Finally, the limitations discussed would vary depending on country, for some regions within Africa, there might by high rural electrification rates or they might have better access to markets than other. The location of groundwater resources also varies spatially, some countries might not have much at all or they might have shallower reserves. Hence a country by country analysis is required when addressing the potential of small scale GWI and taking into account the specific features of that region.

Overall, I think Villholth provides a useful analysis of the suitability of small holder GWI irrigation in SSA, but there are certain limitations to the conclusions she reaches ( discussed above) which should be considered in the case by case context.

Groundwater resource mapping

So following from last weeks post, that suggests there is currently not enough quantification of groundwater resources in Africa, scientists from the British Geological Survey and UCL ( yes, my university is famous) have actually mapped the potential yield of aquifers underlying the African continent.
http://www.bbc.co.uk/news/science-environment-17775211

This research suggests that the current water resources under ground are 100 times that of on the service.

This is great news, now that we know water is there to actually feed the population and help the people as well as provide a buffer to climate change. However how do we actually realize these reserves? We must develop an understanding of the best ways to extract them and transport it to the needed areas.

Is Groundwater a solution?

So over the past few blog posts, we have figured out that Africa actually has enough water to sustain its population, but the problem lies much deeper. Its the uncertainty and high variability, both spatially and temporarily that's creating water stress in Africa.

I think a possible solution is to develop the use of groundwater to foster agricultural production and feed the hungry people. Is this a reasonable approach? We shall find out in the next couple of weeks :)

For this post I will be looking at an article by Giordano 2006, which provides an assessment of groundwater resources for agriculture on the continent.

National estimates of the FAO suggests that African groundwater supplies can be replaced at a rate of 1,500 cubic km /year (FAO 2003). This is much greater than the water availability in countries such as India and China, which have seen a green revolution driven by groundwater. So at a first glance, there is nothing stopping Africa from doing the same.

Data suggests that at present, there are over 1 million hectares being irrigated by groundwater, with 1% of the African population directly depending on it for agricultural production (FAO 1986). In many arid parts of Africa, groundwater plays a vital role in sustaining livestock, forming a basis for human survival. In some countries like Somalia, the groundwater resources are used entirely for livestock and none for crops (Githumbi, in press). With over 10% and 65% depending on livestock directly/indirectly respectively, and given that livestock heavily depends on groundwater, the role and of groundwater as a resource substantial. It is also possible that the contribution of groundwater to livestock is much higher than for crop agriculture.

However much like other water resources, groundwater is highly variable and its quantity depends on a number of factors.

•  Geology: the type of rock determines its capacity to store water, so for example consolidated rock types and volcanic rocks are able to produce high groundwater flow, compared to other types.
• Climatic conditions: hydrological function and distribution of groundwater is connected to rainfall patterns.
• Fossil ground water reserves. 

So although on one hand Africa has plenty of groundwater available, due to geology, the water is located deep under ground and in areas which are problematic to access, thus increasing the cost of exploitation. Moreover, groundwater supplies tend to be located in areas with high rainfall in the first place, thus undermining the whole point of having them. Groundwater currently is concentrated in just 4 countries, creating problems for access and distribution.

Although groundwater is currently used to an extent for farming, particularly in livestock, there are some barriers to fully maximise its development and role in agriculture. These problems should be addressed in the near future, if we are to solve the issue of water in Africa. Moreover I would agree with Giordano in the sense that more research and quantification of groundwater resources is needed, particularly if we want to create a solution. We are in need of actual data on the current usage and contribution of groundwater to agricultural output. This would enable to plan and provide an adequate program for future development of this valuable resource.

Yes there are limitations to groundwater, but on the whole, I would imagine that currently it is one of the possible solutions to water shortages in Africa and to expand crop irrigation.

In my blog posts further I hope to expand the theme of groundwater by looking at its current use in agriculture, what groundwater supply depends on, its future opportunities and whether it is sustainable.


Until next time :)

In the mean time...

Today will be just a short post exploring what's happening in Africa as we speak.

So due to the El Nino effect this year, Africa, particularly the southern part of the continent, is currently experiencing a severe drought. This has had a tremendous impact on its agriculture sector, (17% fall in output).

https://www.enca.com/south-africa/drought-stricken-south-africa-brink-importing-food-agriculture-minister

The government proposes to increase grey water recycling, as a means to augment water availability.

 Whilst this might be a good way to address the immediate drought problems, I really think they should do something substantial to address the water scarcity issue sustainably and for the long term. Africa is in need of a comprehensive water management strategy.

What are your thoughts?