WHILE Lake Kariba – the world’s largest man-made dam by water storage capacity – remains Zimbabwe’s hydroelectricity generation locomotive powering households and the economy, it has a precarious vulnerability: Water levels.
BERNARD MPOFU
This raises fresh urgency for new power projects, especially in renewable energy sector.
Lake Kariba is designed to operate between levels 475.50 metres and 488.50 metres (with 0.70m freeboard) for hydropower generation. It is currently generating between 413MW and 750MW on six units.
However, the lake level has been decreasing steadily due to low inflows from the mainstream Zambezi River, closing the period under review at 478.59 metres (21.58% usable storage) on 12 September, compared to 481.29m (41.49% usable storage) recorded on the same date last year.
As the historical hydrological trend shows, yet compounded by the delayed onset of the 2021/2022 rainfall season, the lake levels receded significantly during the last quarter of 2021 into the first week of January 2022.
However, owing to subsequent steady increase in rainfall activity and associated increase in Zambezi River flows as well as the resultant Lake Kariba inflow, the water rose from 478.23m recorded on 7 January to 478.47m recorded on 17 January, positioning it 2.97 metres above the Minimum Operating Level (MOL) of 475.50m.
This translates into 13.43 Billion Cubic Metres (BCM) or 21% of stored usable water or live storage.
On the same date last year, the lake level was slightly higher at 478.63m with 14.17 BCM or 21.87% of usable storage, with the lake level being three metres above the MOL.
Now the water has drastically gone around 20%.
Zambezi River flows at Chavuma are in recession and closed the period under review at 105m3/s on 12t September. The flow recorded last year on the same date was 132m3/s.
Kariba South has a 1 050MW capacity. The hydroelectric power plant is located on the Zambezi River at the Kariba Gorge. It is currently the biggest power plant by installed capacity in Zimbabwe.
It was originally developed with six generating units commissioned between 1959 and 1962. The facility was expanded by two additional units of 150MW capacity each in March 2018.
Zimbabwe is rich in large deposits of coal resources which are largely underdeveloped or yet to be utilized. The country’s economic potential is underpinned by the best solar radiation, vast biofuels, significant wind potential, perennial rivers for small hydro projects and coal bed methane deposits.
Despite its potential, Zimbabwe is still reeling from power shortages. According to power utility Zimbabwe Electricity Supply Authority general supply updates summary for 16 September, for instance, supply at peak hour was 1 500MW against demand for 1 790MW, yielding a shortfall of 290MW. That meant load-shedding.
On 14 September, total peak supply was 1 262MW versus a demand of 1 770MW, leaving a deficit of 508MW.
Although Hwange has an installed capacity of 920MW, it is currently supply about at least 389MW from its working five units, G2, G3, G4, G5 and G6. G5 manually tripped yesterday, while G1 is on a two months outage for installation of a new burner firing system.
Hwange power station has been operational since 1983.
Scheduled for completion in 2022, the on-going expansion project will further increase the plant’s capacity to 1 520MW.
The power station, which already has six coal-fired generating units, is being expanded with two additional coal-fired units of 300MW capacity each.
The main equipment for the seventh and eighth units of the plant are being provided by China’s state-owned electricity equipment manufacturer Dongfang Electric Corporation.
The power station is expected to generate more than 60% of Zimbabwe’s electricity needs following the expansion.
Despite having an abundance of coal deposits, government and Zesa officials are are deeply worried about the future of coal-fired electricity projects in the country following China’s recent move to stop funding coal energy schemes that are outside its borders to flatten its carbon emissions curve to limit global warming and climate change.
Economies of countries such as Botswana, South Africa and Zimbabwe were constructed on fossil fuel as the primary energy source.
So without coal-powered stations, they would face serious electricity shortages.
For Zimbabwe, the solution on the 10 Gorges Project.
The Central African Renewable Energy Project, the Zambezi and Kafue hydro-electric power imitative, also known as the 10 Gorges Project, is a major investment which needs to be developed to increase capacity and spread risk.
The 10 gorges includes the Batoka Gorge which will cost up to US$5 billion, generating 2 400 megawatts.
The 10 gorges project include Devil’s Gorge (1 240MW), Kariba N-S (2 100MW), Mupata (1 200), Boroma (450), Lupata (850MW), Mpanda Kuwa (1 600MW), Cahora North (1 200MW), Cahora South (2 075), Lower Kafue (750MW), Kafue Gorge (990MW), and the Batoka Gorge.
Those operating are producing 5 915MW, new developing projects (4000MW), Future Gorges (4 940MW) and total installed capacity (14 855).
