Climate change impacts are being felt more keenly by African countries that are sharing water resources for hydropower generation. Recent research underscores the importance of integrating climate change adaptation into transboundary river management discussions
Kariba Dam in Zimbabwe. (Credit: Rhys Jones/Wikimedia Commons)
Climate change may previously have been considered by many Zimbabweans as being “merely academic”, but according to the country’s President Mnangagwa, this is no longer the case. The Zambezi River Authority’s recent decision to limit power generation at Kariba Dam, which has led to curtailed power production and daily power cuts across the country, is a clear sign that the region is suffering from the effects of climate change now, Mnangagwa added.
Writing in a newspaper column in early December 2022, Mnangagwa said that his country is “reeling from severe power deficits”. The 2130MW hydro project, which meets almost half of his country’s power needs, has been impacted by declining water levels at Lake Kariba that are occurring more frequently.
Zimbabwe says it is now turning to thermal stations to meet the shortfall, but this will still be far from the power required to maintain existing capacity in the economy. Refusing to get “sentimental” about using coal, the Zimbabwean President said while his industries are dying from power shortages, limited support for the clean energy transition is being offered by those countries, whom he claims, are to blame for destroying the global climate.
To tackle the current energy crisis, Mnangagwa says his country’s licensing regime needs to be expedited to encourage new players into the renewable sector, while Zimbabwe will also have to engage with other members of the SADC region who have surplus power to export.
Lake Kariba is managed by the Zambezi River Authority (ZRA) on behalf of Zambia and Zimbabwe. ZRA’s principal clients are Zambia’s state power utility ZESCO on the north bank with a 1080MW hydropower plant at Kariba, and the Zimbabwe Power Company (ZPC) on the south with a 1050MW plant.
Annually, the authority allocates ZESCO and ZPC equal quantities of water for power generation at their respective power stations, and both countries are currently experiencing desperate periods of load shedding following the drop in water levels.
Zambia’s President Hakainde Hichilema says the two countries “need to meet in a private family conversation”. He believes that maybe it is now time to review governance documents so Lake Kariba can be better managed to deliver stronger economies for both Zambia and Zimbabwe and to make people happy on both sides of the river.
President Hichilema added that he regrets that one of the two utilities is engaged in “excessive abstraction” of water to the disadvantage of the other, and there is a need to strengthen the authority of ZRA to ensure ZESCO and ZPC operate within their allocated framework for water usage.
In the past, both power companies have exceeded their water allocation. In 2018 they were within theirs, but ZESCO exceeded this in 2019. Then from 2020-22, both power companies continued to use more than their allocation. However, last year, ZESCO exceeded by 0.42%, which is permitted under the Water Purchase Agreement, while ZPC exceeded by 11.12% and attracted applicable over-utilisation penalties.
The river authority says the power companies were advised to use water within their allocation to leave 6% live storage by the end of the year, to support power generation into the second quarter of 2023. However, over-utilisation and poor performance of Kariba’s lower catchment rivers led to low water levels being recorded and, as of 11 January 2023, the lake level was only 0.28m above the minimum operating level.
Until the end of January 2023, ZRA said both ZESCO and ZPC needed to maintain Kariba’s combined average generation output at 500MW (250MW each) after which they could increase to 400MW per power station. The flows of the mainstream Zambezi River are set to further increase during February and March, with lake levels projected to significantly increase by April 2023 in line with peak flows of the river.
Zambia’s President Hichilema doesn’t want to dwell on the past but wants to “see how we can do better going forward”. He also adds there is a need to expedite repair works to the plunge pool at Lake Kariba to ensure the structural integrity of the over 60-year-old dam wall is maintained. The work is part of the ongoing US$294 million-dollar Kariba Dam Rehabilitation Project which started in 2017 and also includes refurbishment of six spillway gates.
Looking to the future, ZRA says it wants to take full control of the water intakes to both Kariba power stations “in order to effectively regulate the utilisation of water”. This will mean the immediate closure of inlet valves as soon as water usage exceeds the acceptable threshold. There are also plans to review penalties for exceeding water allocation, while discussions are underway to speed up the development of upstream reservoirs, such as the Batoka Gorge Hydro-Electric Scheme and Devils Gorge Hydro-Electric Scheme, to improve operations and pursue synchronisation with other dam operators.
Grand Ethiopian Renaissance Dam
Uncertainties surrounding climate change and its impact on the management of the Nile River system have led to the development of a new analytical framework that can provide economic benefits for affected countries.
Historically, water infrastructure projects have been constructed on the Nile for water supply, flood control and hydropower generation purposes, mostly in Egypt, Sudan and Ethiopia. Over the past two decades, Ethiopia has been increasing its use of the Nile for hydropower generation and constructing the Grand Ethiopian Renaissance Dam (GERD) on the Nile near the Ethiopian–Sudanese border.
The dam is expected to result in a range of opportunities and risks to Sudan and Egypt, triggering political tension between the three countries. Negotiations have so far failed to reach agreements over how to fill the reservoir and water sharing during times of drought, while concerns centre on the fact that the total storage capacity of the GERD is equivalent to 1.5 times the historical mean annual river flow at the dam location. Indeed, negotiations have not even considered the impact of climate change.
Research led by The University of Manchester and published in Nature Climate Change has developed a unique river modelling software which combines climate projections; hydrological, river system and economy-wide simulators; and artificial intelligence multi-objective design and machine learning algorithms to design adaptive plans for various climate change situations.
The authors say that analysis of the GERD’s initial filling and long-term operation shows that adaptively managing the dam to maximise the national benefits of any of the three countries would be costly for at least one of the other two countries. However their adaptive management approach “could produce balanced benefits for the three countries”.
“We demonstrate the utility of the framework by designing a cooperative adaptive management policy for the Grand Ethiopian Renaissance Dam that balances the transboundary economic and biophysical interests of Ethiopia, Sudan and Egypt,” Mohammed Basheer et al say in their paper. “This shows that if the three countries compromise cooperatively and adaptively in managing the dam, the national-level economic and resilience benefits are substantial, especially under climate projections with the most extreme streamflow changes.”
Furthermore, the authors believe it “is high time” to integrate climate change adaptation into the decade-long negotiations over GERD and broader Nile management discussion between the 11 riparian countries.
“Nile negotiations have aimed to produce static long-term agreements, but there is high uncertainty on the medium and long-term impacts of climate change on the basin’s rainfall, streamflow, temperature, and socio-economic systems – this paper proposes an analytical approach that can help design adaptive agreements given these uncertainties,” says Dr Mohammed Basheer, lead author of the paper.
Impacting water supply
Various countries across Africa are described as feeling the effects of a changing climate. Extreme heat conditions across South Africa have caused evaporation at the province’s reservoirs leading to a decline in water levels, the Department of Water and Sanitation reported on 26 January 2023. Spokesperson, Wisane Mavasa said high temperatures in various parts of the country have had a negative impact.
“While the current dam levels should not be cause for concern, the continuous drop in some parts of the country remains a worry, and the low levels will affect water supply to communities. We are therefore encouraging communities to conserve water and be extremely cautious when using dams or rivers to cool off from these hot weather conditions.”
Although national dam levels were showing a slight improvement on last year’s figures for the end of January, and the country’s water supply systems are now “mostly on high levels”, they are also “experiencing a continuous drop” as the rainy season comes to an end. Western Cape Province is reported to have one of the lowest levels that had “drastically” dropped down to just over 56% of capacity.
The Department of Water and Sanitation is also dealing with other concerns in relation to water resources and usage. It says it “continues to tighten its firm hand on illegal water use” as a farmer in KwaZulu-Natal was fined R1.5 million for constructing an illegal dam on his farm without the required water use authorisation. The department has also called upon communities to “be active citizens and guard their own infrastructure” as vandalism of water supply facilities continues to undermine and derail government efforts to ensure water security to communities. It says that the disruption of water supply as a result of vandalism in the Amathole District Municipality has exacerbated the ongoing challenges in the area due to water demand that exceeds water supply, plus the effects of load shedding.
Tunisia and Morocco
Drought has also been taking hold on Tunisia for the past three years. Dams are reported to be at 25% of capacity, with some as low as 10%, and since September 2022 only a fifth of normal rainfall has been recorded. Farmers are worried about food supplies and fear for their crops of olives – the country’s most important export.
While some are saying it is time for the authorities to declare a state of water emergency, Tunisia says it is preparing studies for the development of new dams and seawater desalination plants between 2023-25.
Repeatedly lower winter rainfall is also causing problems in Morocco. After five consecutive years of drought, many of the country’s reservoirs are at lower levels, with the government now instructing that most water will now be diverted from irrigation to supply drinking water. In previous years water supplies were cut to homes at night to help ensure they lasted throughout the summer months.
This article first appeared in International Water Power magazine.