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.