Kariba Dam water levels continue to decline
IF I had not been there to witness it with my own eyes, I would not have believed that Kariba South Hydroelectric Power Station, which for more than 60 years has been producing dependable and cheap electricity for the country is no longer yielding a positive return.
Now, after my visit to the resort town of Kariba last week, 390 kilometres northwest of the Harare, my fear that the plant could face a possible shutdown, has been confirmed.
And it seems hard to imagine the State-run power utility is moving towards investing in more expensive imports to maintain its electricity supply.
Kariba South Hydroelectric Power Station’s general manager, Kenneth Maswera, heightened my fears when he disclosed last Friday that the dam would only generate power for the next five months and, if water levels kept falling, it would completely stop producing electricity.
What quickly came to my mind was the case of Tanzania, which last year in October was forced to shut down all its hydropower facilities across the country for nearly a month because water levels in its dams had fallen too low to run turbines.
Kariba Dam, a source of water for power generation for ZESA Holdings and Zambia Electricity Supply Corporation (ZESCO), which share the water resource, was designed to operate between levels 475,50 metres and 488,50 metres above sea level.
At the end of the year, Kariba Dam water levels were 478 metres, but the levels were 477,15 metres above sea level on Friday last week, just 1,65 metres above the minimum water generation threshold.
At this level, Kariba South Power Station can only generate on average 285 megawatts (MW) a day.
This raises the threat of painful power cuts in the two countries, which are already faced with frequent power shortages.
“We are hoping that we will be getting a bit of water since the rainy season has started in our catchment, but that water will take about three months to reach us,” said Maswera.
“If water goes below 475,50 metres, we can no longer get water to turn the turbines to generate electricity.
“So, as I speak today (Friday), our level is 477,15 metres. This means the amount of water which is available for electricity generation is 1,65 metres above the minimum level (475,5 metres). This situation last happened in 1992.
“If you have been to Victoria Falls, I am sure you have seen that there is a bit of some flow. This year, we have tried to show the lake level week by week.
“Ordinarily, we should have started the year at 484 metres going up — that’s the normal — but look where we are at 477,15 metres and the level has been almost constant but going down. That’s a fact. There have been some inflows, but we are drawing for generation. But basically this is an indication that it’s most likely that the level will continue to go down.”
The plummeting water levels in the iconic Kariba Dam, one of the world’s biggest man-made wonders, have since exposed the lake’s bed at some places, while never seen before big rocks and anti-vortex beams have been exposed from the depths.
Zimbabwe and Zambia equally share 64,74 billion cubic metres of Kariba’s 180 billion cubic metres for electricity generation.
When the lake is full, Kariba South Hydro Power Plant is able to generate 750MW. But capacity has come down to 285MW due to the low water levels.
This has since forced the Zimbabwe Power Company (ZPC), a power generation unit for ZESA, to revise its generation pattern to ensure it meets demand for power at the appropriate time and also save water.
To save water, ZPC shuts down five units at night and remains with one that produces about 100MW.
It is understood that each machine, when running, requires a massive 150 cubic metres per second of water, which translates to a stunning 900 cubic metres of water per second when all six units are running.
In the morning, at around 04:30 hours, production starts to go up to about 400MW.
Zambezi River Authority (ZRA) chief executive officer, Munyaradzi Munodawafa, painted a grim picture of the situation.
“The situation we have is very bad. When we look at the trend, it’s slightly above what we experienced in 1995. That year, the lake level was far worse than this. But obviously there wasn’t that much generation like what we are having today. That’s why we were at least not worried.
“In terms of the lake level, it’s not good because it’s going down. The trend is likely to continue until around the beginning of May. That’s when we are likely to experience at least a bit of a change, but it’s not going to be much. So in terms of improvement in terms of lake level or anything else, we are not going to have it this year,” said Munodawafa.
He added: “We have seen graphs going up in terms of the water upstream of the Zambezi. Like in Chavuma, we are having about 2 000 cubic metres per second of water flowing into the Zambezi from the Angolan side.
“But now, that water has to pass through the Barotse plains (wetlands) and these (Barotse) plains are thirsty and all that water is being gabbed in the planes. When the plain are satisfied they will then release the remainder of the water. So if you go to Victoria Falls, the same flows after the Barotse plains as we speak, per second, we have got about 500 cubic metres of water flowing. That’s the amount of water which is more or less to get into the Lake.
“But, at the lake, we have two stations (Kariba South and North) consuming between 900 and 1 000 cubic metres of water per second. So in terms of the lake level it’s not good. Actually, it’s going down.”
According to the rule curve, if things are normal, Kariba Dam’s water level starts to go up in January, a situation attributed to local inflows.
Zimbabwe contributes about 20 percent of the inflows into the lake.
Munyati feeds Sanyati River, which then supplies water into the lake, but those rivers are hardly flowing due to poor rainfall across the country.
The other source is Gwaai River. Again it is not flowing. This means there have not been significant inflows into the lake.
From the other sources in Zambia, Angola and the Democratic Republic of Congo, the inflow into the lake normally comes in March or May.
The development comes at a time when ZESA is battling machine breakdown at its four thermal power stations in Hwange, Harare, Munyati and Bulawayo.
The small thermals were commissioned between 1946 and 1958 and have since passed their design life, which is 25 years.
They are now in a deteriorating state with most of the plants requiring either life extension measures or complete replacement.
Consequently, their generation capacity has seriously declined.
The last unit of Hwange Power Station was commissioned in 1987, which is more than 25 years ago.
Electricity shortages have forced local industries to use costly diesel generators to keep operations running and have been blamed for keeping away potential investors, analysts say.
Experts said the hydropower shortfalls could result in ZESA suffering losses of about US$500 million.
Asked if the power utility was not concerned with the Kariba situation, ZESA spokesperson, Fullard Gwasira, said despite dwindling water levels at Kariba Dam, the power utility has prepared for the possibility of halting generation at Kariba.
In terms of its fallback position, ZESA is considering the importation of electricity from South Africa, Mozambique and Zambia.
The power utility has plans to establish an emergency diesel power plant at Dema in Seke District and will also soon implement the solar water heating programme among many other mitigatory measures.
“It’s a fact that the amount of water for generation we have (at Kariba) has come down. In terms of losing value, there is no dispute about that, but this situation is being managed well,” said Gwasira.
“As management, we are not sitting on our laurels. Yes, there is nothing we can do about water. But remember that Kariba is important because it dilutes the tariff. If we remove Kariba, we go back to about US$0,14 per kilowatt hour.
“At the same time, we can’t talk of waiting for rain to fill up Kariba, that’s not management. So we are saying if we have to shut down Kariba, how do we run ZESA to serve the nation? So as management, we are not just relying on water. We have several measures we have put in place in order to mitigate the severity of not having enough water to generate electricity at Kariba.
“These measures include power imports from Eskom (300MW), from Mozambique, we get 50MW and from August 1 (this year) we will be importing about 56MW from Lusenfwa of Zambia and then at the end of the year, we will import 100MW.
“These are all initiatives we are putting in place to augment the power shortages. From Eskom, they can give us gas but what makes this deal (with Eskom) lucrative is that the rand is going south against the US dollar. As we prepay in US dollars, we (ZESA) become a premium customer because they are getting foreign currency,” Gwasira explained.
Apart from the supply side, Gwasira said ZESA was also looking at the demand side to manage the electricity supply deficit.
“I am sure you are aware that we have installed more than 500 prepaid meters. Plans are also at an advanced stage to introduce solar geysers which will take a lot of stress from the national grid.
“It’s also important to say we expect all our customers to prepay for power because we are also prepaying for imports which should also assist us to sustain this improved reliability of supply system which we are witnessing at the moment. So these cocktail of initiatives should be able to address power shortages, but notwithstanding that during the winter peak period, we do get challenges in terms of power supply.
“We talk about the expansion of Kariba South Power Station, but that’s not the only initiative that is happening. We are also considering diesel plant in Dema that will give us about 200MW. People might say this power from diesel is expensive, but we will blend it with thermals and Kariba, whatever the amount (from Kariba).
“There is Hwange Power Station project and a lot is happening in small thermals. But the beauty of all this is that government has allowed other players (independent power producers) to come in.
“So all these cocktail of measures should be able to see us through. In fact, we should be in an excess position before 2020,” said Gwasira.
Meanwhile, the US$533 million Kariba South Power Station expansion, was now 40 percent complete.
The project, which includes development costs to be met by ZPC, is being undertaken by a Chinese firm, Sino Hydro and is targeted for completion by 2018.
The project is going to bring two machines each 150MW to the existing 750MW. When completed, the plant will be able to generate about 1050MW.
ZPC is expected to commission unit seven on December 24, 2017 while unit eight should be commissioned on March 10, 2017.
ZPC has also replaced transformers and switch gears at the existing plant at Kariba to improve on reliability at a cost of US$25 million.
Other projects are Gairezi Hydro Power Project to produce 30MW, solar projects to produce 300MW, Mutare peaking power plant to produce 120MW, coal-bed methane gas to produce 300MW, Hwange 7 and 8 Expansion to produce 600MW and together with other works on existing plants.
ZESA has also requested the Zimbabwe Energy Regulatory Authority (ZERA) to allow it to raise the electricity tariff from US$0,0986 per kilowatt-hour to cover the increased costs of importing additional power and emergency power to sustain the economy.
Government last reviewed electricity tariffs in 2012.
Kariba South Power Station has been supplying electricity at an average cost of US$0,02 per kilowatt hour (kw/h) while the four thermal power stations at Hwange, Harare, Munyati and Bulawayo have been generating power at an average cost of between US$0,08 and US$0,16 per kw/h.
The high costs are due to inefficiencies at these thermal power stations, associated with ageing equipment, a situation which makes the domestic production of electricity relatively expensive compared to regional counterparts.
Zimbabwe is importing 300 megawatts from South Africa’s power utility Eskom at a cost of US$0,13 per kilowatt hour, while Hydro Cahora Bassa of Mozambique is supplying 50MW at US$0,0614.
In the past four years government has suppressed a tariff adjustment at the expense of power utility, ZESA Holdings, which is sinking deeper into insolvency.
It has, therefore, been difficult for the parastatal to service its debts while at the same time investing in new capital projects in the wake of frequent breakdowns of its ageing electricity plants.
Currently, the tariff is pegged on average at US$0,0986 per kilowatt hour, which is insufficient to support power projects currently underway.
In 2013, consultants, Norconsult, came up with a cost of US$0,14 per kilowatt hour, but issues of efficiency at the country’s thermal power stations have affected the actual cost of electricity.
In comparison, South Africa has a five-year rolling tariff whereby the tariff is increased gradually at a certain percentage in order for the country to reach a cost reflective tariff.
In other words, South Africa increases the electricity tariff every year. Last year, South Africa increased its tariff by 25 percent.
ZERA is, however, still consulting electricity consumers before making a decision on ZESA’s tariff request.
“We are expecting to get an increase in power tariff because if it’s not increased Zimbabweans would have chosen the amount of load-shedding they want. Does it make sense to have electricity twice a week?” Gwasira asked.
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