Adapting to Climate Change: Groundwater

Climate change largely influences surface water sources through altered rainfall patterns, evaporation rates and changing temperatures, whereas groundwater resources are more resilient to climate change and thus offers a reliable supply of water (Calow et al., 2010). Groundwater resources can provide an important buffer to climate change because despite aquifers being highly unevenly distributed across Africa, the smallest or poorest aquifers can still contain enough water for pumping to local communities during dry rainfall seasons or long periods of drought (MacDonald, 2012). In this blog, I would like to explore how groundwater resources respond to climate change and thus the role of groundwater resources as an adaptive measure.

Groundwater resources typically store a certain amount of water depending on the geology, geomorphology, and effective rainfall of the aquifer, which in turn influences the transmissivity, porosity, saturated thickness, and recharge rates of the aquifer (MacDonald et al., 2012). The largest aquifers in the African continent lies in the northern region, where countries like Libya, Algeria, and Egypt have the largest reserves of groundwater (Figure 1). Aquifers with lower storage capacities varies across the continent due to different rock formations; the lowest groundwater storages are underlain by Precambrian basement rocks (MacDonald et al., 2012). However, despite some areas having large or small storage capacities, the yield of the aquifer and borehole limit the productivity of these aquifers. The yield of a borehole or hand pump to the aquifer will limit how much water can be abstracted and used, therefore even though some countries have large aquifers, the productivity of these aquifers may be low where little water can be abstracted and used. Figure 2 shows the productivity of aquifers, and comparing this to figure 1 for example, shows that the aquifer underlying the South Sudan region has a relatively high groundwater storage of 25,000-50,000 mm, however it has a moderate productivity level of 1/5 ls^-1. 

Figure 1. Groundwater Storage (MacDonald et al., 2012)                         Figure 2. Aquifer Productivity (MacDonald et al., 2012)

Climate change rarely impacts the geology and geomorphology of groundwater resources; however, climate change directly influences groundwater resources through groundwater recharge processes (Taylor et al., 2012). The replenishment of groundwater resources relies upon recharge from either rainfall or the leakage from surface water resources. The IPCC’s fifth assessment report predicts that rainfall patterns are likely to become more highly variable, both spatially and temporally where droughts and intense rainfall periods are likely to occur (IPCC, 2014), and this in turn will likely influence groundwater recharge.

A study by Owor et al. (2009) attempted to determine a relationship between groundwater recharge and climate change using a rare set of data, which consists of daily rainfall and groundwater levels in the Upper Nile Basin of Uganda. The study related the magnitude of recharge events to the sum of daily and annual sum of daily rainfall exceeding a threshold of 10mm^-1, and they have found that groundwater recharge is better related to heavy rainfall periods, exceeding a threshold of 10mm^-1, compared to daily rainfall rates. Their conclusion of this analysis suggested that climate change may indeed have a positive influence on groundwater recharge because the predicted increased frequency in rainfall intensity can promote increases in groundwater recharge instead of restricting it. Similarly, another study by Mileham et al. (2009) found that groundwater recharge was higher when intense rainfall was accounted for when modelling the influence of climate change projections on groundwater recharge. A mean monthly delta factor of climate change was applied to the SMBM while using a historical rainfall distribution (period 1960-1990), groundwater recharge is projected to decrease by 55%, whereas runoff is predicted to increase by 86%. However, when this historical rainfall distribution is adjusted to account for the projected increase in intense rainfall patterns for a future period (2070-2100), groundwater recharge and runoff is predicted to increase by 53% and 137% respectively. Hence, this also shows that groundwater recharge is positively influenced by intense rainfall, and the distribution of daily rainfall is also an important factor when modelling groundwater recharge.

These studies have shown that the projected intense rainfall will likely improve groundwater recharge and thus the amount of groundwater stored. This in turn can prove to be a reliable source of freshwater, especially during periods of drought. An article by Oliver Balch (2016) agrees that the increased use of Africa’s aquifers can help to reduce water stress and insecurity. Initiatives by the International Water Management Institute and the Groundwater Solutions Initiative for Policy and Practice aims to enhance the use of groundwater resources for agricultural and domestic needs, to reach the UN Sustainable Development Goals in reducing water scarcity. However, the article stresses the importance of overexploitation and sustainable consumption of groundwater, noting that the Saiss aquifer water table has fallen by an annual average of 3meters over the past 20 years (Balch, 2016). It is important to recognise that despite groundwater being a reliable source and adaptive strategy to climate change, it is important that groundwater use is sustainable. A study by Knuppe (2011) conducted interviews with management experts in South Africa to determine the key challenges in the sustainable use and management of groundwater resources. Climate change will have uncertain consequences on groundwater resources but the stress and exploitation on this resource will increase due to the undervaluation of groundwater, the need for information at all levels in a community, the centralisation of power, governance and management, and the disregard for ecosystems and its services. A water planning expert, Callist Tindimugaya in the Balch article says that groundwater resources are an “invisible commons” because there is a lack of information amongst the people using this resource, and thus they do not comprehend how to use this resource sustainably. A lack of central planning and policies leads to inefficiencies, and ultimately poor management resulting in intensive and exploitative use of groundwater. Therefore, it is also important to consider the combination of socio-economic and physical context of using groundwater resources, especially when using groundwater as an adaptive strategy to climate change. 

Climate Change, Land Use and Agriculture

Agriculture is a very important aspect of many people’s livelihoods in Africa, and my previous blog explored the impacts of climate change on agriculture and the vulnerability of Africa’s population to these impacts. Addressing the impacts is definitely an important aspect to maintain people’s livelihoods, but now I am interested in exploring the future of Africa’s agricultural sector in terms of land use change. How does climate change influence the way land is used? What are the drivers for land use change and to what type of land use is being used? What are the implications on hydrological processes and water availability if land is increasingly being used for agriculture? These are some questions that I would like to explore.

Land use change and climate change are both factors that contributes to global environmental change, however, both of these factors affect each other (Dale, 1997). Firstly, land use change and patterns influences climate change due to changes in the atmospheric flux of CO2 and secondly, land use can be altered by climate change due to unfavourable conditions for certain human uses and activities. Hence, land use can be seen as a causal factor to climate change, but it can also be seen as an adaptive measure to climate change (Dale, 1997).

The World Bank estimates that as of 2013, approximately 43.86% of land in Sub-Saharan Africa is used for agricultural purposes. Agricultural transformation in Africa has an important role for economic transformation and in recent years Africa has seen large increases in investment by governments in this sector. Africa Agriculture Status Report (2016) explains that Africa’s agricultural sector is driving changes in Africa’s economic prosperity, and hence these socio-economic drivers will continue intensify the changes in land use for agricultural purposes. I will not go into detail about the history and development of Africa’s agricultural sector in this blog, but instead, I would like to highlight another an alternative driver of land use change in Africa. 

Ahmed et al. (2016) highlights the importance of climate change as another important factor in shaping agricultural land use. As previously mentioned, Dale (1997) explains that there is a dual relationship between land use change and climate change, and Ahmed et al. (2016) models both socio-economic and climate change factors as the drivers of Africa’s agricultural future. The study found that a reduction in crop yields caused by climate change, alongside an increasing demand for food in the future will inevitably result in an increase in land used for agriculture in West Africa to meet these demands. The eastern region of West Africa will experience a decline in both forests and grassland covers to cropland covers, whereas the western region will experience a larger decline in forest cover overall. The study projected that for Nigeria, average cropland cover will increase from 39.4 to 84.5% as a result of climate change, and an increase in crop cover of 37.3-40.9% is likely to occur along the Gulf of Guinea. These results show that under a purely climate change scenario, land use change will move from natural vegetation to crop cover, however, these results were determined without accounting for the adaptive capacities of farmers and communities. This study does mention these limitations and it was useful in attempting to show how much land will change as a result of climate change, but we cannot simply ignore the combination of other socio-economic factors and adaptive strategies of farmers to climate change scenarios, which this study concludes as the largest factor in driving land use change.

Changing land from one land cover to another is likely to have large implications on water resources, and especially in arid and semi-arid regions of Sub-Saharan Africa. Evaporation and runoff components of a catchment are usually influenced the most by land-use change, which in turn influences runoff and recharge rates into aquifers. A case study in southwest Niger shows that the water table has been increasing for many decades, despite there being a decline of 23% of the monsoonal rainfall seasons (Favreau et al., 2009). This was because land clearing of natural savannah to be used for millet crops had significantly increased surface runoff; the study modelled runoff and concluded that runoff had increased by threefold the normal rate, irrespective of climate conditions. Higher rates of runoff leads to higher recharge rates, the study found that recharge rates increased to 7mm/area after land was cleared compared to a rate of 2mm/area before land was cleared for crops. Not only does land use change influence rates of recharge and runoff, it also affects the quality of groundwater resources whereby there was a rising trend in nitrate concentrations by 4% (Favreau et al., 2009). Hence, when decisions are made to convert natural land to agricultural land crops, the impacts of this change needs to be carefully considered, especially because of the impacts of water resources and if these impacts will infringe upon the sustainability of that resource.

Concluding thoughts:

Land use change, climate change and water resources has more complicated drivers, interactions and consequences than has been explored in this blog. In this blog, I wanted to focus on the climate perspective of land use change and the consequences of this change, but despite making attempts to just focus on this perspective, I could not ignore the socio-economic drivers that influences land use change. Indeed, when analysing the drivers and consequences of land use change, one should look at both the human and climate factors of this change. Undoubtedly, land use change will have consequences on water resources such as groundwater levels and the quality of water resources and so farmers will need to carefully consider why they are changing land-use for agricultural purposes and if it will outweigh the consequences of water resources. 

Climate Change Impacts on Agriculture

In my previous blogs, I have discussed the impacts of climate change on rainfall patterns. In this blog, I want to explore how these changes in rainfall patterns will affect Africa’s agricultural sector and the economic and social consequences of changing agricultural yields and productivity.

A huge concern of climate change impacts in Africa especially is centred on food security. Food security is understood as the physical and economic access to safe and sufficient food to meet dietary needs (FAO, 2006) and climate change threatens to worsen food security conditions. Africa’s economy and people relies largely on agricultural products for their economy or sustenance and the prospects of climate change altering rainfall patterns poses a large threat to Africa’s agriculture because crop production relies hugely on rainfall to water their crops. Many large organisations such as the Food and Agriculture Organisation of the United Nations, the World Bank or the International Food Policy Research Institute (IFPRI), have all predicted that the prospects of Africa’s agricultural sector are bleak. For example, the FAO reports that rural development is expected to be hit hardest due to financial downturns and food crisis associated with loss in agricultural productivity. The FAO predicts that agricultural yields will reduce by up to 50%, and therefore, crop revenue will decline by as much as 90% by 2100 (FAO, 2009). The World Bank estimates that sensitive crops to high temperatures such as maize and wheat would be highly effected and thus crop yields will diminish. Furthermore, arable land would decrease by 40–80% (WorldBank, 2012). Similarly, IFPRI (2013) predicts that crops such as wheat will diminish in productivity, although increases in rainfall in certain areas are likely to experience slightly increased rain-fed maize and rice crops. Overall, these predictions share a common trend whereby crop productivity and yields are expected to decrease, and in conjunction with Africa’s population estimated to increase to 2 billion people within the next few decades (AfricaRenewal, 2014) will only worsen the food crisis and security in Africa. However, I should caution that the impacts of climate change on agriculture will vary across Africa just like how the impacts of climate change on rainfall patterns also vary across the African continent.

These predictions from the FAO or the WB are continent wide predictions which ignores regional scale differences, although, IFPRI estimates that Southern Africa is expected to be one of the worst hit by climate change due to rising temperatures and declining rainfall levels (2013). Countries like Malawi for example are predicted to see declines in average yields in maize productivity by 7–14% by 2050 due to an overall decline in rainfall (Msowoya et al., 2016). Countries in Eastern Africa are experiencing the same decline in crop productivity but in a different manner aside from an overall decline in rainfall. Instead, the Manyoni district in Tanzania are experiencing lower crop productivity due to unpredictable rainfall whereby delays or earlier onsets of the rainy season leads to poor germination of seeds and thus total crop failure (Lema & Majule, 2009). Moreover, problems such as increases in the number of pests and diseases contributes to declining crop productivity.

The consequences of declining crop productivity affect the social and economic conditions of countries in Africa. In Sub-Saharan Africa, agriculture accounts for up to 50% of GDP in most countries, however agricultural practices are small scale, has low inputs with limited use of fertilisers and high dependence on rainfall (Asafu-Adjaye, 2014).
Msowoya et al. (2016) study has identified a strong correlation between Malawi’s maize productivity and the national GDP. From 2000 and 2005, low rainfall levels reduced overall maize productivity and in 2005, maize production was 40% below the national average. This decline in productivity was followed by a large decrease in the national GDP production potential from maize. Given that Malawai’s food production is highly dependent on rainfall, and maize is a core crop in agriculture, the impacts of climate change has large ramifications on the socio-economic standing of Malawi. Lower productivity will inevitably increase the prices of crops and this can worsen conditions for poor groups of people who may no longer be able to afford to pay for crops. An overall decrease in crop productivity places stress of socio-economic development in areas that need it, and it also places stress in urban areas for alternative to agriculture employment opportunities.

Interestingly however, most agricultural output in Sub-Saharan Africa and the associated economic value is influenced not only by rainfall conditions, but technological and market conditions in Africa. The opportunities in agricultural output that fertilisers can provide are not seen due to the lack of using fertilisers because of its high prices (Asafu-Adjaye, 2014). Furthermore, farmers who does not have access to larger markets to sell their goods to, or the technology and means to store their goods effectively eliminates the potential of achieving high transaction costs due to the need to sell their products immediately. Rural markets are less likely to benefit from trading with larger markets due to segregation and isolation.

Concluding thoughts

The direct impacts of climate change such as the lack of rainfall as well as the temporally and spatially variable rainfall patterns has huge consequences on agricultural output, which is an overall declining trend across Africa. This can worsen economic and social conditions whereby the national economic output can decline; individual farmers have lower levels of income thus affecting social conditions such as the ability to pay for electricity or school and daily necessities. Moreover, lower agricultural output can result in the migration of people from rural farming lands to urban areas in search of other jobs, further complicate living conditions in these areas. There is no doubt that climate change has the potential to affect agriculture, but it is also important to recognise that human structures and policies can play a large part in an agricultural economy, and the vulnerability of small scale and large scale farmers.