The future of groundwater

                                                                        

When assessing the suitability of groundwater use for agriculture, we must look at a range of factors including the resilience of the water resource to climate change.

According to IPCC, average temperatures in Africa are likely to increase in general, “annual mean air temperature between 2080 and 2099 is expected to be 3-4o C higher than it was between 1980 and 1999” (Calow 2009). Increased frequency of extreme events (droughts and floods) is expected. Changes in precipitation and evaporation will affect changes in moisture deficits, surface water runoff and hence have an effect on groundwater. It has been suggested by Taylor et al (2009), that a “shift toward more intensive precipitation enhances groundwater recharge”.  Given the high uncertainty in future surface water run-off, groundwater may become a strategic tool of adapting to fluctuations in fresh water supplies.

Thereby being resilient to climate change makes groundwater a sustainable resource and one which could be used to develop small holder irrigation, improving food security. However as discussed in the literature previously, for groundwater to be an effective solution, I believe more government involvement is required to address the issues of inequality, assisting with initial financing of small scale irrigation schemes in order to achieve a reliable source of water for use in agriculture. Finally, due to natural variability, a country by country analysis must be done in order to maximise the value of groundwater use in each case.

Overall groundwater has a high potential to contribute to resolving the water crisis in agricultural sector and achieve food security. Whether this potential is maximised however will depend on the decision making of government and other institutions.

Pump Irrigation

In today's post I will discuss how motorised pumps are involved in Small Scale Irrigation in Africa, advocating agricultural development.

Due to the technological change and assistance from World Bank, in many African countries particularly Nigeria, motorised pumps have largely replaced traditional irrigation systems such as shadoof and calabash. After surveying 250 households on the Hadejia-Nguru floodplain, 56% have now converted to using pumps, with 30% of these have not previously irrigated during the dry season. (Kimmage and Adams 1990)

Technical Description

• 2-3in large, and can be carried on the back of a bicycle.
• Operating lift of 6-8m but can deliver 12-30m if needed.
• Discharge: 4litres/s for 2in pump with tubewell, or 23l/s for 4in pump from open water.
• Average irrigated plot size- 0.7-0.9ha (Singh 1986)
• Estimated working time 3/4 years, lifetime of 300-600 hr per year.

Costs and Benefits of Pumps

Purchase costs offset by high returns- pumps are economically attractive to small farmers. ADP research suggests the pump cost can be covered in 1-2 seasons.

However there are high maintenance costs associated with the pumps, in Bauchi State 40% of pumps broke down within first year, with 23 days lost due to breakdowns (Chapman 1984).There is also great difficulty in obtaining spare parts for pumps and these are usually very expensive and thus unaffordable for many small farmers.

 (Kimmage and Adams 1990) also note that pump irrigation is also closely tied to the market, due to high capital costs farmers are avoiding planting low value crops in order to obtain higher profits. This leads to increasing market imbalances, as increased overproduction of high value crops,created oversupply, resulting in distortion of prices from equilibrium and hence farmers receive a lower price for their crops than initially. 

Although there are some limitations, pump irrigation allows farmers to be increasingly flexible and adapt to market opportunities. The ban on wheat imports in Nigeria in 1997 with a following price hike, created an incentive for farmers to switch to wheat production due to availability of pump irrigation. Moreover because they can now plant during the dry season, farmers have seen an increase in agricultural output, as a result of rapid expansion of cultivated areas. They are now able to plant all year around,not just for 6 months of the year. 

Overall the article raises some important concerns about the nature of pump irrigation, with an analysis of the limitations and welfare benefits of this system for small scale groundwater irrigation. However I believe that it misses out some important questions, with regards to suitability and sustainability of pump irrigation. I think that the extent to which farmers benefit from motorised pump will primarily depend on their access to markets, and how easily they can sell their crops to others. This will largely determine if they actually have an economic profit from their production. This is of course constrained by a whole range of other factors, ie transportation, infrastructure etc. Finally (Kimmage and Adams 1990) suggest that the costs of pumps may be initially too high for farmers, and expensive to maintain. They mention that some subsidies are in place to help them overcome this difficulty, but is there anything more governments could do to advocate more pump use? Such as reducing price, more subsidies/grants, assistance for maintenance ? I think that if pump irrigation is actually effective, governments should do a lot more to expand it amongst poorer farmers and assist them in acquiring the technology that would benefit them in the long term. The sustainability of this should also be noted, if the system is too troublesome, maybe they should look into development of more simple and easy technologies that doesn't require intricate parts or a lot of fuel to power the irrigation. This is something I will look into in the next post :)

What are your thoughts so far? Do you think that this is a reasonable approach to advocating groundwater irrigation?

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?

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.