This story was supported by Pulitzer Centre

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Persistent and severe droughts have drastically curtailed Lesotho’s capacity to produce its own hydropower, shoving the country into a perennial power crisis.

The droughts have reduced the water levels at Katse Dam, Africa’s second-largest dam, which powers the turbines at Muela Power Station. Mohale Dam, which feeds Katse Dam, has also experienced extended periods of low water levels.

The results are severe: lack of drinking water and reduced hydropower generation capacity. Lesotho is thus struggling to meet its energy needs and the 1986 Treaty’s obligations to supply water to South Africa.

The Drought Dilemma: Water levels and power generation

Data from the Lesotho Highlands Development Authority (LHDA), which oversees the Lesotho Water Highlands Project (LWHP) and the country’s hydropower operations, indicates a steady decline in water levels at the Katse and Mohale dams over the decade from 2014 to 2023.

Over this period, water levels in these two dams averaged 60%, with the lowest levels recorded in 2019.

Data shows that the Katse Dam declined significantly, reaching only a third of its capacity, while in October 2020, the Mohale Dam fell to its lowest level of 11%.

These low water levels have impacted electricity generation at the ‘Muela Hydropower Station in Botha Bothe district, which operates three generators to produce 72 megawatts a day.  But, when water levels in the two major dams feeding the power station are low, the reduced pressure on the turbines results in lower power output.

The consequences are clear: energy production fell dramatically over the decade between 2014 and 2023 and, although there was a slight increase in production in 2021, hydroelectricity production in Lesotho has not returned to its peak in 2015 when 532 190 megawatt-hours were generated.

“The worst drought was in 2019 where we were unable to meet the water delivery target and power generation targets as well. During the other drought periods, the LHDA [Lesotho Highlands Development Authority] was able to meet the targets,” said LHDA Public Relations Manager, Mpho Brown.

Inside the ‘Muela Hydropower Plant

The battle for power: imports and shortages

The ‘Muela plant is the main source of power in Lesotho, but it is not the only one. A 30-MW solar farm, which is in Mafeteng and funded by China, also adds to the grid. However, its contribution is not only limited to the fact that it only produces power during the day but is unable to store electricity generated. 

The reality for Lesotho is that, even if it the ‘Muela plant produces all 72 MW that it is capable of each day and if the solar plant adds another 30 MW to that, this 102 MW produced each day is still way short of the 160 MW the country needs each day.  Lesotho plugs this gap by buying the remaining around 58 MW from South Africa and Mozambique at a much higher cost than its own produced power.

The ‘Muela plant has shut down for six months, from October 2024 to March 2025, so that maintenance on transfer and delivery tunnels can be done. This means no water is being transferred to South Africa during this period and no electricity is produced at ‘Muela and Lesotho relies on 100% imported electricity at night.

A delicate balance – power generation and water levels

‘Muela plant depends on water from the Katse and Mohale dams, both constructed under phases 1A and 1B of the LWHP. The dams are connected for two-way transfer of water and Katse dam feeds the power plant through a 45-kilometre-long tunnel. Water levels affect the amount of power the plant can generate.

When the water levels are high, the plant can exceed its nominal rating of 72 MW. Each of the three generators can generate up to 30 MW, making a total of 90 MW possible. But, when the levels drop, it can’t produce as much. In extreme cases the turbines are forced to work harder to maintain output, quickly depleting the remaining water in the dams.

According to Brown, Katse Dam levels started dropping in 2015, as a result, hydropower production reduced because the head was decreasing. This is corroborated by analysis of the dataset supplied by the LHDA on Katse Dam and Mohale Dam levels from January 2014 to December last year.

At Mohale Dam, water levels have been low for a prolonged period, according to the statistics. Data further shows that half the time between January 2014 and December 2023, water levels have been below 51%. On average, water levels stood at 43% over a 10-year period and most of the time, the water levels could not exceed half but improved only in 2021 and peaked in 2022.

Similarly, the same picture was painted by Katse Dam. Between 2014 and 2023, Katse Dam water level was unstable but started declining significantly from 2015 to late 2019, signalling a protracted drought period.

Data shows that in Katse Dam water levels started dropping in percentage terms from record levels to an average of 93% in 2015 and never recovered until seven years later. It improved significantly at the beginning of 2018 to reach the 80% mark, but declined steadily over the rest of the year to a third  – or around 30% –  in October 2019. Katse Dam’s water level remained at a critical level in 2020 and peaked in 2021.

When Katse dam levels drop during extreme droughts, electricity generation at ‘Muela plant also goes down, according to Poloko Sephelane, the LHDA’s Senior Engineer, Operations and Maintenance based at ‘Muela Plant. “This is the same when dam levels rise, electricity production also goes higher,” Sephelane added.

“Each of our generators has a nominal rating of 24 MW. When dam levels are at their full capacity, we can reach as high as 30 MW from one generator. But if dam levels keep declining, even the electricity output declines to the ultimate minimum of 24 MW.

He said for instance, guide vanes could open at 70% to allow the inflow of water into electricity generation system and give 20 MW when dam levels are high, but with lower dam levels, the opening must go beyond 70% for more water but give the same number of megawatts.

“This means with lower dam levels, more water is needed to give one megawatt as pressure needed to turn turbines is lower than when the head is higher,” Sephelane said, adding that in 2019, they had the worst experience and failed to meet targets as they were generating at lower pressure.

“This was quickly draining our dams as a higher volume was needed to reach the generator’s 24 MW capacity,” said Sephelane.

Climate changes the future of hydropower

A climate change vulnerability assessment conducted by the LHDA between 2022 and 2023 confirms that the outlook for Lesotho’s energy future is uncertain. 

The study found that Lesotho, thanks to global climate change, is likely to experience more severe droughts. Rising temperatures will reduce rain and snowfall flowing into the rivers and dams, particularly the Senqu basin, which all supply Lesotho’s hydropower plant.

“If nothing is done, there could be less water flowing through the LHWP system, affecting both hydropower generation and water transfer to South Africa. This could impact the royalties collected by the government of Lesotho from water transfers and decrease energy security,” warned Brown.

Renewable future

Despite the challenges, there is still hope for Lesotho’s energy crisis. The country has significant potential for other clean energy, including wind, solar and from biomass sources.

With a growing push for renewable energy, Lesotho aims to reduce its reliance on fossil fuels and power imports by developing a diverse mix of energy sources.

The Lesotho Energy Policy (2015-2025) aims to increase independence through the development of both large and small scale energy projects, including micro-hydro, wind and solar power plants.

A key component of the LHDA strategy, according to Brown, is the implementation of a comprehensive wetlands and rangelands rehabilitation and conservation program in the LHWP catchments. “This initiative is further supported by plans to declare the headwaters of the LHWP catchments as protected areas to enhance the project’s resilience to climate change impacts,” he added.

“However, with multiple interventions for climate adaptation and the LHDA’s Integrated Catchment Management interventions, together with the government and partners such as ReNoka, the project is doing what is possible to ensure sustainability and conservation of the catchments, water sources and to reduce impacts on the wetlands and rangelands that are the lifeblood of the water in the LHWP system and Lesotho’s water as a whole.”

While the road ahead is challenging, there is huge potential for sustainable energy sources in Lesotho.

As Brown puts it: “It is the LHDA’s priority to ensure that the future of hydropower is protected, and that is an effort for not just the Lesotho Government but also other regional governments in the ORASECOM who are beneficiaries of the Senqu/Orange River Basin.