Addressing the energy-water nexus in Southern Africa

19 May 2017

With vast hydrological resources, the pressure of growing population, increasing energy investments and the threat of climate change, the World Bank believes it is now time to understand and harness the energy-water nexus in Southern Africa.

The interrelationship between water and energy supply, water resources and climate change is particularly relevant to decision making in Southern Africa, says a recent report published by The World Bank as a background paper to support dialogue in this region of the world.

“The region’s water resources are unevenly distributed both spatially and temporally, leading to significant water scarcity in some parts of the region and relative abundance in others,” the Bank explains. “There is also limited knowledge about the region’s overall water resource levels. Climate change is expected to reduce rainfall levels, increase rainfall variability, and increase ambient temperatures, but there is little certainty about when and by how much. In light of these spatial differences, water and energy sector planning needs to be approached in tandem at a local, national, river basin, or regional level, depending on the nature of the issue.”

Entitled The Southern Africa Energy-Water Nexus, the report covers all countries in the Southern Africa Development Community (SADC), while looking at five focus countries in depth – South Africa, Lesotho, Botswana, Namibia and Swaziland. Covering an area of 555,000km2, the SADC region has a population of approximately 277M. And it’s population growth, along with urbanisation and its associated increase in well-being and economic growth, will place increasing pressure on water and energy resources.

Southern Africa is described as being characterised by an uneven distribution of economic well-being, water resources, energy production capacity and potential climate change impacts. It is this unevenness, the World Bank says, which gives rise to geographic areas of resource stress and abundance, and is why the nexus is of particular relevance to decision making.

Hydrological resources

Hydrological resources in the region are very unevenly distributed. The southernmost countries—South Africa, Botswana and Namibia—receive much lower levels of rainfall than the northern countries, such as DRC, Angola and Zambia. Differences across the region are as large as 2000mm/yr.

Characterised by 15 major transboundary river basins, more than 70% of the region’s freshwater resources are shared between two or more countries.

According to the report: “The issues and implications that surround the energy-water nexus are numerous. The use of electricity and water as critical inputs to economic activity, implies that there are many interlinkages that can be explored…. In the context of major energy investments expected in Southern Africa, the scope of this paper is focused specifically on the subset of the nexus addressing electricity supply. Water is important for hydropower generation and for cooling in thermal generation plants. Electricity is needed to advance various stages of the water supply and sanitation value chain. Energy and water security are thus strongly interlinked and should be recognised as so by planners, policy makers, and investors alike.”

The region is described as being well endowed in terms of energy resources. Historically, coal has been the source of most power generation activity in the east and northeast regions of South Africa. Other generation does exits and the region has the potential for 56,000MW of hydropower in DRC and Mozambique alone. Ultimately, different forms of energy generation will have very different implications for regional water demands.

Changing climate

Several studies have shown considerable uncertainty about the likely impacts of climate change on the region and its water resources but, the report claims, recent evidence suggests they could be significant. For instance, the effect of El Niño during 2015–16 has led to a more than 50% reduction in power generation output from the Kariba Dam on the Zambia–Zimbabwe border and Swaziland. The bank’s report gives more details about this:

“The Kariba Dam is situated on the Zambezi River and straddles the border between Zambia and Zimbabwe. It is the largest constructed reservoir in the world, by water storage capacity, and has been a key source of regional energy security since its commissioning in 1960. The Kariba Reservoir supplies water to two underground hydropower stations, with a total capacity of 1830MW generating more than 10,035GWh of electricity annually.  Power output potential at Kariba is directly related to the overall reservoir water level, which is a function of Zambezi River inflow. Lower than expected rainfall levels in late 2014/early 2015, as a result of El Niño, led to the reservoir being reported at just 11% full on 27 January 2016 (compared with being more than 50% full at the same time the previous year). As a result, potential annual power generation has been reduced by more than 50% to 4060GWh, strongly highlighting the need for regional investment in climate-resilient projects.”

As similar situation was experienced in Uganda during drought conditions of 2004-5. This led to a large drop in the level of Lake Victoria which acts as a natural reservoir for the hydropower facility at the Nalubaale (formerly Owen falls) and Kiira dams.

A report by the McKinsey Global Institute in 2011 not only explains how climate change set off a damaging chain reaction in Uganda, but also highlights the interrelated and complex nature of the energy-water nexus in this region:

“After the extreme and prolonged drought of 2004 and 2005, Lake Victoria’s water level dropped by one metre in 2006. This reflected not only evaporation and low rainfall but also the fact that so much water had been removed from the lake to fuel generation of electric power at the Owen Falls dam. With less water available for Owen Falls, Uganda was forced to ration power for both industrial and domestic use. This has had a negative impact on the entire economy. To meet electricity demand, the government started using expensive thermal power. Electricity tariffs per unit of domestic consumption nearly doubled. Higher electricity prices have increased pressure on forest resources. Around 95% of Ugandan households use wood fuel to meet at least some of their energy needs, and exorbitant power tariffs only heightened the population’s dependence on tree and forest products for fuel. Demand for wood fuel has outstripped supply, and the process of the charcoal and wood fuel have [sic] rocketed. The heavy cutting of forest, coupled with the unsustainable slash-and-burn practices, has contributed to the degradation of land and soil, leading to poor yields on food crops and threatening Uganda’s food security”

Furthermore, a study to forecast changes in the physical performance of hydropower in the Congo and Zambezi river basins (Cervigni et al in 2015) found that, in the driest of scenarios, failure to integrate climate change in the planning and design of power and water infrastructure could entail significant losses of hydropower revenues, plus increases in consumer expenditure for energy. This study went on to add:

“Focusing on the Zambezi river basins, the study found that the effects of climate change on river flow and evaporation rates could have a significant impact on future hydropower output. The worst-case scenario could see a loss of baseline revenues of up to 18%, while the best-case scenario could see gains of 6% on baseline revenues. However, the best-case scenario is unlikely to be fully realisable with current power-trading agreements and transmission infrastructure. Given the impossibility of predicting actual climate outcomes, the study advocates investment in “worst-outcome avoidance” through changes in generation capacity and water-use efficiencies. Practically, this could involve a mix of responses across the two basins, including investing in additional generation capacity, increasing water-use efficiency, and downsizing facilities to avoid underutilisation in dry climates. For the Zambezi river basins, avoiding the worst-case outcome could reduce baseline revenue losses from 18% to 10%.”

Discuss, agree and identify

The World Bank report says that the region needs to bring together stakeholders to discuss the nexus, agree on key priorities for cross-sectoral coordination, and identify who the main champions are to help address each of these.

The Bank is optimistic that the shared water resources through the region’s large transboundary river basins and significant history of electricity trade, could create a potentially strong regional dimension to address national water and energy priorities. However, it cautions that cross-sectoral linkages and the transboundary nature of water resources also put an onus on good governance – effective and harmonised planning and decision making. Poor governance can have serious consequences. All decisions need to take into account these cross-sectoral linkages, and the institutions overseeing these decisions need to be equipped to do so.

Another key challenge is accommodating climate change uncertainty when making investment decisions. Climate change could have a significant impact on water and energy systems. The current state of knowledge is described as being inadequate for “understanding the likelihood of various future scenarios and the quantification of associated impacts”. This introduces deep uncertainty into decision making regarding the energy–water nexus.

The strong interdependency between the two sectors and fundamental uncertainty about the impact of climate change make robust long-term nexus planning very challenging. As a result, decision makers may have to adapt their approach to investment planning, opting instead for solutions that minimise potential losses under a range of climate change scenarios.



Information for this article was obtained from Report No: ACS19178. Southern Africa Energy-Water Nexus. Background Paper to Support Dialogue in the Region. Published by The World Bank. June 2016.

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