The Impact of Climate Change on Hydropower in sub-Saharan Africa

(A literature review prepared for the Advanced Level Climate Change Course at Budapest University of Technology and Economics 2021/22 academic session)

Abstract

A duality exists between hydropower and climate change. While hydropower is a reliable renewable energy resource with significant contributions to lowering greenhouse gas emissions, climate change negatively impacts water availability, posing a challenge to hydropower generation. Over 160 million electricity consumers in Sub-Saharan Africa live in a country where hydropower is responsible for more than 50% of the total power supply. Thus, the energy security of Sub-Saharan Africa must be addressed as energy is critical to enhancing climate resilience and overall long-term development. Resilient hydropower can also help the region achieve the Sustainable Development Goals (SDGs), shift to sustainable energy, and adapt to climate change.

Introduction

Energy security is necessary to improve the adaptive capacity and climate resilience of any region. Unfortunately, inadequate generation capacity and efficiency, insufficient energy infrastructure, and low access to power supplies continue to be significant challenges in most parts of sub-Saharan Africa (“The role of hydropower in Africa’s vision,” 2014).

Hydropower has been a vast energy resource in the region for a long time. It accounts for more than 80% of energy generation in several sub-Saharan African nations, including the Democratic Republic of Congo, Ethiopia, Malawi, Mozambique, Uganda, and Zambia. It also accounts for about 80% of the total non-fossil energy generation across Africa (IEA, 2020).

However, in recent years, prolonged drought as a result of climate change has already had adverse consequences in many of these hydropower dependent countries in the region, including Tanzania, Ghana, Zambia, Kenya, and Zimbabwe, causing prolonged and frequent power outages and business losses (Falchetta et al., 2019). Thus, the availability of water is an increasingly potent risk to sub-Saharan hydropower generation.

Figure 1: (a) represents the map of sub-Saharan Africa showing the total installed hydropower capacity. (b) illustrates the share of hydropower as a percentage of the total domestic power generation in 2016. (Falchetta et al., 2019)

Changing climatic patterns in sub-Saharan Africa

Two-thirds of the African continent is covered in arid regions, and the bulk of the continent receives high heat for much of the year. While dry regions are diverse in terms of land patterns, soils, fauna, vegetation, water balances, and human activities, they are generally characterized by insufficient and erratic precipitation, as well as severe temperatures (Welborn, 2018). Seven climatic zones are generally recognized in Africa (Figure 2). Within these broad categories, countries and regions have distinct climates attributed to differing altitudes, climatic zones, and other localized variables (Eriksen et al., 2008).

Figure 2: The climate zone of Africa (Jim Angus, 1997)

Changes in climate variables such as precipitation, temperature, and extreme weather events such as droughts and floods in the sub-Saharan Africa region have been characterized as dramatic by many studies, and it has been predicted to continue in this way in the foreseeable future (Kotir, 2011).

Temperature Changes

In the twentieth century, Africa recorded an average annual rise in temperature of 0.5°C. However, these changes are not evenly distributed across the continent. For example, during the second part of the century, temperatures in the Nile Basin grew by roughly 0.2°C to 0.3°C every decade, while temperatures in Rwanda increased by 0.7°C to 0.9°C (Kotir, 2011). According to climate models, the median temperature increase across the continent is expected to be within the range of 3°C to °C, about 1.5 times the mean global increase. The heart of the Sahara’s semi-arid edges and central southern Africa are anticipated to see the most future warming (Eriksen et al., 2008).

Precipitation Changes

Precipitation plays a crucial role in maintaining the atmospheric balance, water level, and availability. Lack of precipitation can cause drought, while excessive rainfall can also lead to catastrophic floods. Large-scale intra-seasonal and inter-annual climate variability and the occasional El Nino-Southern Oscillation (ENSO) events in the tropical Pacific influence rainfall patterns in sub-Saharan Africa. As a result, frequent extreme weather events like droughts and floods occur, reducing agricultural outputs. (Kotir, 2011). Changes in precipitation are expected to cause drying in southern Africa and increase rainfall in parts of eastern Africa. Although there is scant research on changes in severe events in Africa, there is evidence of an increased likelihood of strong rainfall events and accompanying floods. On the other hand, surface runoff is expected to decline during the next century as a result of both increasing rainfall and increased evaporation owing to warmer temperatures. Droughts are becoming more common in the drylands of southern Africa, and they are anticipated to worsen as a result of rising temperatures and less rainfall (Eriksen et al., 2008).

Impacts of climate change on sub-Saharan Africa

Africa will be one of the hardest-hit regions by climate change (IPCC, 2007). Low adaptive capability, inadequate distribution of technology and knowledge critical to enabling adaptation, and a strong reliance on agriculture for livelihoods are all factors contributing to Africa’s susceptibility(Welborn, 2018).

Rising sea levels and coastal erosion

Although, there is regional variation in sea-level change across Africa. In numerous oceanic locations encircling the continent, sea-level rise surpassed 5 mm per year. In the south-western Indian Ocean, from Madagascar eastward to and beyond Mauritius, it exceeded 5 mm per year, surpassing the 3-4mm global sea-level rise (UNCC, 2020). Rising sea level is expected to cause saltwater intrusion and coastal erosion by the end of the century. Some of these climatic changes might have catastrophic consequences if they compound current strains like water scarcity and climatic variability like decadal drying episodes. Uncertainty about the direction and extent of changes in precipitation, river flows, and lake levels, in particular, makes adaptation to climate change difficult (Eriksen et al., 2008)

Occurrence of Extreme Weather Events

Natural disasters in sub-Saharan Africa are often caused by too much or too little rain (Brown and Crawford 2009, cited in (Kotir, 2011)). Droughts, severe rainstorms, flooding, forest fires, and ENSO events are expected to become more frequent and intense due to rising temperatures and the unpredictability of rainfall (both temporally and geographically). Currently, it is estimated that about one-third of Africa’s population lives in drought-prone areas and is sensitive to its effects (World Water Forum 2000, cited in (Kotir, 2011)).

Food Security

According to IPCC forecasts, warmer climate scenarios might have disastrous consequences for agricultural output and food security (IPCC, 2007). Reduced crop productivity due to heat and drought stress and increased pest damage, disease damage, and flood impacts on food system infrastructure are all significant concerns for agriculture, with severe consequences for food security and livelihoods at the regional, national, and individual household levels. Major grain crops farmed across Africa will be negatively impacted by the middle of this century, with geographical variations and changes across crops. In the worst-case climate change scenario, West and Central Africa would lose 13% of their average yield, North Africa would lose 11%, and East and Southern Africa will lose 8%. Rice and wheat would be the most impacted crops, with 12 percent and 21 percent output losses in 2050, respectively (UNCC, 2020).

Water Availability

Climate change is anticipated to exacerbate prevailing water-related issues in the region. Intense rainfall events will worsen present water stress, diminish the quality and amount of water available for home and industrial usage, and limit hydropower output in many locations. The Nile basin countries’ water supply relies on runoff from the Ethiopian highlands and the level of Lake Victoria, both of which are subject to rainfall changes (Eriksen et al., 2008). While the influence of climate change on water shortages may be minimal compared to socioeconomic changes like increased demand, land cover change, and economic growth methods, it may have international ramifications and become a cause of conflict (Eriksen et al., 2008).

Impact of hydropower on climate change in sub-Saharan Africa

Hydropower plays a significant role in climate mitigation and adaptation. It is clean, renewable, and significantly more environmentally friendly than conventional energy sources. Hydropower contributes to reducing three gigatons of CO2 per year, representing 9% of the global annual CO2 emissions (Berga, 2016).

Hydropower is the most cost-effective renewable energy source, and it is frequently cost-competitive with current market energy costs. Although it requires a somewhat large initial investment, it has a long lifespan and minimal operating and maintenance costs. Hydropower also boasts one of the highest conversion efficiencies of any known energy source (about 90 percent efficiency, water to wire). Hydropower also has a great level of dependability, flexibility, and variety in project scales and sizes, allowing it to suit both centralized urban and industrial demands and rural needs (Berga, 2016).

In the context of Integrated Water Resources Management, hydropower storage capacity can offer security for irrigation, drinking water supply, flood control, and navigation services. By ensuring the availability of water supplies, hydropower storage in multifunctional dams would aid climate change adaptation of sub-Saharan Africa (Berga, 2016).

Impact of climate change on Sub-Saharan hydropower

Power is generated by hydropower by harnessing the potential energy of falling water to rotate a turbine connected to a generator. The amount of power generated is a function of the hydraulic head and the flow characteristics. Because turbines require vast amounts of water to create power, hydropower output is inextricably related to water availability (Falchetta et al., 2019).

Climate change particularly poses a threat to many current and proposed hydroelectric projects, as many of these projects may still be operational in 50 or even 100 years, when the consequences of climate change may be significant in certain situations. Long-term infrastructure, such as hydroelectric systems, is less responsive to climate change since it is difficult to update such infrastructure retrospectively (Lumbroso et al., 2015). Some of the effects of changes in selected climate variables on hydropower are discussed below:

Rainfall and River Flows

Climate change is likely to alter rainfall patterns as well as river flow variations and discharges, posing a threat to hydropower generation. Changes in rainfall and river flows and their geographical and temporal patterns may extend or shorten the time when turbines may run at full power.

Temperature and Humidity

Changes in air temperature and humidity may cause increased evaporation rates from reservoir surfaces, reducing the amount of water available for power generation.

Droughts and Floods

Droughts and floods pose a significant risk to the power sector. During drought years, hydropower utilization rates drop by over 5% (Lumbroso et al., 2015). Increased flood magnitudes may increase the likelihood of dam breaches due to spillways failing to safely convey the flood flow, putting people downstream at risk.

Sedimentation

Increased sediment loads in rivers as a result of more severe rains would speed up reservoir sedimentation, resulting in storage loss and turbine blade damage.

Vulnerability and Sensitivity of Sub-Saharan hydropower to climate change

Vulnerability is defined as the magnitude and rate of climate variability to which a system is exposed while considering its sensitivity and adaptive capacity (IPCC, 2007). Hydropower is particularly sensitive to climate change because of its sensitivity to water supply, which is generally limited in Africa. Only 9% of the world’s renewable freshwater resources are found in Africa, with half of them concentrated in only six African countries (UNESCO, 2019). Water shortages have already occurred in several towns in Mozambique, Zimbabwe, and Ghana in 2019 (IEA, 2019). Because of the shortage of water, hydroelectric power typically has to compete with other water users.

Given the increasing danger of water stress owing to changing and irregular precipitation patterns, competition for water between energy, residential, and productive uses is projected to heighten in some regions. (IEA, 2020)

Challenges and Opportunities

Diversification of Energy Resource

Over-reliance on hydropower may increase the vulnerability of sub-Saharan Africa to electricity outages during extreme weather events. Non-hydro RE (renewable energy) sources offer the advantage of generating electricity without contributing to greenhouse gas emissions while having a far less impact on water supplies and lowering greenhouse gas emissions. They can also assist service irrigation demands in the agriculture sector by extracting water (e.g., water pumping) and reducing competition for reservoirs in dry areas. Hydropower may also serve as a solution for energy storage (as reservoir water) to meet demand peaks and seasonality if correctly designed in conjunction with intermittent RE like solar and wind (Falchetta et al., 2019).

Climate Technology and Skills Gap

In terms of climate technology, Africa and small island developing states have the most capacity shortages. For example, Africa also has the world’s least established land-based observation network (UNCC, 2020). Improved weather forecasting technology in Sub-Saharan Africa is critical for informing climate change responses as well as decision-making related to adaptation to climate change (Youds et al., 2021).

Conclusion

Although hydropower has been a largely reliable and clean energy source for the region, climate change may pose a great threat to hydropower-dependent countries’ energy security. It is essential to improve the climate resilience of hydropower in the sub-Saharan region to support the provision of an uninterrupted electricity supply, which is key to improving the overall adaptive capacity of the region.

Also, the electricity supply should be diversified. Hydropower, wind energy, and solar energy offer significant synergy since wind and solar power are intermittent and highly variable, but hydropower can balance fluctuation and meet peak demand. Furthermore, hydropower in pumped storage power plants can store energy in a significant and effective way.

Also, promoting multifunctional dams (electricity generation and water-saving reservoir) and improved planning tools for multipurpose water projects should be prioritized. This would enhance hydropower utilization as a source of clean energy as well as water-saving.

References

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Falchetta, G., Gernaat, D., Hunt, J., Sterl, S., 2019. Accepted Manuscript Hydropower dependency and climate change in sub-Saharan Africa: A nexus framework and evidence-based review Hydropower dependency and climate change in sub-Saharan Africa: a nexus framework and evidence-based review. https://doi.org/10.1016/j.jclepro.2019.05.263

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