Zambia’s Electrical Power Paradox: Balancing Exports with Hydropower Sustainability

By Dr Roy Moobola

Zambia’s energy sector faces a delicate balancing act. While increased electricity exports have earned vital foreign currency, such gains are juxtaposed against the real threat of unsustainable water usage at Kariba Dam. The El Niño-induced drought of 2024 has underscored the vulnerabilities of Zambia’s hydropower system to climate variability, leading to significant power imports and economic strain.

This article delves into the interplay between rising exports, domestic energy demand, and hydropower water management challenges, offering insights into how Zambia can ensure sustainable energy generation in the face of mounting risks.

Electricity Generation, Consumption and Exports

The graph below, which spans the years from 2013 to 2023, illustrates Zambia’s electricity generation, consumption, and exports. Over this period, electricity generation has shown relatively steady growth with dips in the drought-affected years of 2015, 2016, 2019 and 2020. Average annual growth in generation has been 3.8% over this ten-year period. The sustained rise in generation reflects recent investments in new infrastructure, including the commissioning of Maamba coal-fired power station in 2016 and Kafue Gorge Lower hydropower station in 2021.

On the consumption side, there has been a similar pattern of growth, with an average annual increase of 3.2% over the ten-year period to 2023, driven by rising domestic and industrial demand together with wider electrification efforts.

Electricity exports, meanwhile, have exhibited a less consistent pattern being roughly steady up to 2020 but have surged sharply in recent years. From 2020 onwards, electricity exports have grown by an average annual rate of 40%, signalling Zambia’s increasing role as a regional energy supplier.

Figure 1: Variation of Zambia’s Electricity Generation, Consumption and Exports between 2013 and 2023

Generation by Major Power Stations

The next graph provides a detailed breakdown of electricity generation by major power stations from 2014 to 2023. It reveals the pivotal roles played by Zambia’s major hydropower plants – Kafue Gorge Upper, Kariba (North Bank and North Bank Extension), and Kafue Gorge Lower – as well as the Maamba coal-fired power station which together account for between 80% and 90% of total electricity generation each year.

Kafue Gorge Upper has been the largest and most stable contributor to the country’s electricity generation. Output at Kariba has shown significant variability due to low dam water levels, highlighting the vulnerability of this critical plant to climatic variability and high water usage.

The commissioning of Kafue Gorge Lower in 2021 added substantial new capacity, bolstering overall generation and offsetting some of the declines at Kariba. Meanwhile, Maamba has provided a consistent thermal generation alternative, ensuring some diversification in Zambia’s energy mix.

Exports are also highlighted in this graph, with their sharp rise from 2020 to 2023 ostensibly fuelled by the additional output from Kafue Gorge Lower and Maamba, allowing Zambia to meet growing regional demand and earn much needed hard currency.

Figure 2: Zambia’s Electricity Generation for Major Power Stations compared with Exports (2014 – 2023)

Kariba Dam Water Management

The next graph highlights water availability and usage at Kariba Dam from 2014 to 2024, emphasising the impact of climate variability. Annual Zambezi River flows fluctuated between 9 and 50 billion m³, but the high flow in 2021 presented a missed opportunity to replenish dam reserves due to excessive water usage. Lower river flows than usage in 2022 and the El Niño event of 2024 have further reduced water levels, eventually causing electricity deficits. Critical lows in dam water levels (below 10% of dam capacity) were recorded in 2019, 2022 and 2024, underscoring the strain excessive water usage places on Kariba’s sustainability.

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Figure 3: Net Zambezi River Flow, Electricity Generation Water Usage and Water Levels for Kariba Dam (2014 – 2024)

Are Exports the Problem?

One pertinent question raised by these trends is whether prioritising electricity exports contributed to the depletion of water levels at Kariba Dam. While domestic consumption has been met by increased generation over the past decade, it would appear that exports have been supported largely by new plants like Kafue Gorge Lower and Maamba, not solely by Kariba’s water reserves.

However, failure to replenish Kariba’s water reserves has left the sector vulnerable to drought, leading to reduced generation capacity and severe load shedding in 2024. Rapid export growth, outpacing generation, has clearly added pressure on water resources.

A calculation of the impact that increased exports have had on water resources at Kariba is shown in the table below.

Table 1: Excess electricity exports and equivalent Kariba Dam water in 2021 – 2023 period compared to the 5-year average from 2016 – 2020

From 2021 to 2023, Zambia exported 5479 GWh of electricity above the average export levels of the previous five years, using an estimated equivalent of 29.1 billion m³ of Kariba Dam water – equivalent to 45% of storage capacity at Kariba Dam. Conserving this water by maintaining historical export levels could have strengthened reserves, providing greater resilience against future water shortages like the 2024 El Niño-induced drought.

By mid-2024, electricity generation had dropped 15% compared to the same period in 2023, likely resulting in a 2900 GWh electricity deficit for the year. The excess power exported in 2021-2023 would have been enough to cover this deficit entirely, potentially preventing load shedding.

Risk Modelling

The next plot illustrates the calculated probability distribution of annual water flow volumes at Victoria Falls, a critical upstream flow point for Kariba Dam. The key data of interest is the estimated river water flow for 2024 of 17 billion m³, which is statistically identified as a 1-in-14-year low-flow event.

Figure 4: Probability distribution curve for annual Zambezi River Water Flow at Victoria Falls (1925 – 2023)
Datapoints are total water flow for stated year (Jan-Dec). Source of data: https://observablehq.com/@westernpower/kariba

The probability distribution shows that extreme low-flow years, like the estimated 2024 volume, are not unprecedented even in living memory, though they are relatively rare. Recent historically low-flow years, such as 1996 and 1995, emphasise the potential recurrence of these events and the vulnerabilities of hydropower systems to climate variability. A 1-in-14-year event indicates a significant risk that must be accounted for in hydropower water management and planning.

Conclusion

To mitigate future risks, Zambia must adopt a multi-pronged strategy to ensure energy security while preserving water resources.

• Investments in alternative energy sources such as solar power should be accelerated to reduce dependency on hydropower.
• Export policies should prioritise domestic energy needs during and following low-flow years, implementing limits on exports when water reserves fall below critical thresholds.
• Improved risk-based water resource management is essential in optimising hydropower water usage.

These measures can help Zambia balance its role as a regional energy supplier, leveraging its water resources to generate foreign exchange, while safeguarding its own economic stability and energy security.