Hydropower in Africa: Plans for new dams could increase the risk of disruption to electricity supply

Low water levels in Malawi

Low lake levels at Cape Maclear in Malawi in early November

Malawi’s state owned electricity company said last week that power output had plummeted after a severe drought. Malawi relies heavily on hydropower. Generation reportedly dropped by half when water levels in the Shire river fell, resulting in power outages across the country.

Our new research published in Nature Energy this month underlines the importance of considering rainfall patterns when planning the location of new hydropower dams and warns that the location of planned dams could put the electricity security of large parts of southern and eastern Africa at risk.

Hydropower power generation is likely to grow rapidly in sub-Saharan Africa

Hydropower represents a significant source of electricity production in eastern and southern Africa. Currently 90% of national electricity generation in Ethiopia, Malawi, Mozambique, Namibia and Zambia comes from hydropower.

The share of hydropower in the energy mix is likely to grow further driven by national and regional energy plans like the Programme for Infrastructure Development in Africa (PIDA). The PIDA estimates that generating capacity needs to increase by 6% per year to 2040 from a current total of 125 GW to keep pace with rising electricity demand.

Several major new developments have been commissioned over the last decade, including the Grand Ethiopian Renaissance Dam on the Blue Nile. Once complete it will increase generating capacity by 6000MW. If all the dams planned for 2030 are constructed they will more than double electricity generation capacity across southern and eastern Africa.

Though new hydropower infrastructure will increase generation capacity in eastern and southern Africa, our new research shows that the locations of the planned dams could put the security of supply at risk.

The majority of dams planned for 2030 will be vulnerable to the similar patterns of rainfall variability

If all the large dams that are planned are constructed, by 2030 70% of total hydropower generating capacity in eastern Africa will dependent on areas with similar patterns of rainfall. In southern Africa 59% of hydropower generation will depend on areas with similar rainfall patterns.

Using rainfall data and grouping areas with similar rainfall variability, we found three different rainfall patterns in eastern Africa. We found seven in southern Africa.

Mapping the location of current and planned dams we found that in each region the majority of dams are concentrated in areas which share a similar pattern of rainfall. These areas experience wet and dry years in the same pattern. Most dams are also heavily concentrated in the Nile and Zambezi river basins.

This could create a significant challenge for these regions, which rely on hydropower. Rainfall variability, in the form of dry and wet periods which can last for several years at a time, is an important feature of much of Africa’s climate. If many dams depend on the same rainfall patterns they will be vulnerable to the same variations – for example drought.

River flow in many of Africa’s river basins is highly sensitive to changes in rainfall. Hydropower expansion programmes will also face the problems of a changing climate.

Changes in the intensity and duration of extreme weather events is already putting global infrastructure to the test. Assessing resilience of infrastructure is a matter of strategic importance.

If the majority of hydropower generation relies on the same rainfall electricity supply could be at risk

Hydropower relies on the flow of water to drive turbines to generate electricity. Water flowing from a high to low elevation, for example from a reservoir behind a dam, can drive the turbines. Drought or successive dry years could result in insufficient water to drive electricity generating turbines and a shortage of electricity.

There are past examples of where reductions in electricity production have been associated with drought, including this month’s blackouts in Malawi. Malawi, Tanzania, Zambia and Zimbabwe also experienced electricity outages due in part to dry conditions during the 2015–2016 El Niño.

Sharing power generation between regions could help secure consistent hydropower supply in semi-arid regions

Although our research finds that within regions hydropower is reliant on the same rainfall patterns, between regions rainfall patterns differ.  This means that new regional power sharing mechanisms (which are call ‘Power Pools’) could provide a means to buffer variations in river discharge or reservoir storage through electricity trading.

At the moment, energy trade is very limited in the Southern African Power Pool and mainly bilateral in eastern Africa, but plans for increased trade are ambitious and hydropower will form a large proportion of new generating capacity.

However, there are significant infrastructural and political challenges to these power-sharing systems. Sovereignty issues expressed as concern about national energy security represent an important challenge to energy trading. Linked systems can have more operational efficiency and hazard mitigation. However, weak cooperation and institutional capacity could limit returns on investment and management effectiveness.

Hydropower and infrastructure plans should incorporate climate risks

Rainfall variability is just one cause of electricity supply disruption. However, our research highlights that it could be a significant challenge for southern and eastern Africa. Guidelines to incorporate climate risks into infrastructure planning are now emerging. They should consider the location of dams and rainfall patterns and how changes in rainfall could affect hydropower supply.

The increasing importance of hydropower, growing concentrations of dams in linked river basins, and potential for more rainfall variability due to climate change, underline the need for effective hydropower planning in Africa.

The paper Hydropower plans in eastern and southern Africa increase risk of concurrent climate-related electricity supply disruption was published 8 December 2017 in Nature Energy.