Impacts of climate change on hydrological extremes and hydropower production in tropical Africa: catchments of Lake Malawi and the Shire River in Malawi

The study investigates the sensitivity of water resources, droughts and hydropower generation to climate change in the Lake Malawi and Shire River basins, covering three different aspects:

• Analysis of the variability and trends of meteorological and hydrological droughts based on observational data from 1970 to 2013;
• Drought analysis for future conditions and investigation of potential changes in water balance and various drought indicators;
• Hydrological simulation and sensitivity analysis of the Lake Malawi water balance and water level, as well as its discharge and associated hydropower generation in the Shire River.

The key findings of these analyses are:

• Between 1970 and 2013, meteorological droughts have increased in intensity and duration. This can be attributed to a decrease in precipitation and an increase in temperatures and evaporation.
• The hydrological system of Lake Malawi reacts to meteorological droughts with a time lag (up to 24 months), so that hydrological droughts can be predicted up to 10 months in advance by meteorological drought parameters. Hydrological droughts are characterized by water levels below 474.1 m asl in Lake Malawi.
• Despite all the differences and uncertainties in climate projections, they agree that meteorological droughts will continue to increase in the future, in the form of increasing drought intensities DI (+25% to +50% for 2021-2050 and +131% to +388% for 2071-2100) and increasing drought months DM (3-5 and 7-8 more drought months per year, respectively).
• The water level in Lake Malawi, as a residual of the catchment water balance, is very sensitive to changes in precipitation and evaporation. Outflow from the lake is a direct function of lake water level, and the combination of projected precipitation decline and temperature increase ultimately leads to significantly reduced flow in the Shire River and a decline in annual hydropower production of between 1% and 2.5% (2021-2050) and 5% and 24% (2071-2100). Sometimes, individual projections even suggest that the outflow from Lake Malawi would temporarily dry up and the power supply in the country would be interrupted.

It is shown that failure to meet the 1.5°C global temperature increase target will have a severe impact on droughts and water resources in Malawi. This in turn has implications for hydropower production, as a result of which the achievement of most of the Sustainable Development Goals (SDGs) will be at risk.