Kariba Dam rehabilitations to start next year, amid fears of cracking

Rehabilitations to the 59-year-old Kariba Dam, Zambia and Zimbabwe’s  the mainstay for mining and industrial consumption of power will start next year with financing provided by cooperating partners.

According to Zambezi River Authority and the Engineering Institute of Zambia, routine maintenance on the dam will begin next year and will last for eight years.

This was after the two countries secured over US$250 million from the European Union, African Development Bank and other partners to sustain the double curvature concrete arch dam.

In recent months there has been concern that the dam could collapse after it developed structures in the walls, a claim Zambezi River Authorities spokeswoman, Elizabeth Karonga, allayed.

Earlier the European Union and the African Development Bank said they were providing a US$250 million loan facility to the two countries to ensure that the concerns at the dam were redressed to avoid affecting the dam’s operations.

However Karonga during a recent meeting of stakeholders in Siavonga argued that efforts are being made to ensure the dam is sustained and ensure all the areas of concern are redressed within the period of rehabilitation.

Karonga maintains the structures were still intact in the 59 year-old dam, constructed by Impressit of Italy for a total of US$480 000.

Zambia Institute of Engineering supports this stating that there is no reason for concern as the dam will not collapse due to current cracks as reported by various stakeholders, which raised fear that more than 3 million people in Zambia, Zimbabwe and Mozambique could be affected if cracks are not repaired within three years.

Engineering Institute EIZ vice-president for policy, public relations and national development George Sitali is cited by the media as saying during a stakeholders meeting that there was no imminent collapse of the Kariba Dam wall.

“Even if these structures were to fail the cracked walls, the structure will not collapse because it’s structurally sound,” the Post newspaper cites Sitali as saying.

Accordingly; “There is no cause for alarm it will collapse. There is no imminent collapse of the dam.”

However, Sitali added that there was need to modernise the monitoring tools for the structural integrity of the wall that makes the biggest man-made lake in southern Africa.

Israel Phiri, a civil engineer, said even if the Kariba Dam wall was attacked by any type of massive flood that occurs once in 10 000 years, it would not succumb.

“If such a flood occurred and all the gates were closed, you would fill up the lake; the water will spill over on top of the concrete dam without causing much damage to the structure,” said Phiri, an expert at hydropower planning and development.

“For me, it’s not threatened; it will be there for a long time to come.”
EIZ recently constituted a team of experts to undertake investigations on the state of Kariba Dam.

During a recent visit to the dam by various stakeholders it was found that the plunge pool scouring had reached depths of the order of 80 metres and if not addressed could lead to undermining of dam wall foundation.

“The present spillway gates do not allow the emergency operation in cases when the downstream gates fail to close, due to deformities over the years,” Sitali said.

“The effects of alkali aggregate reaction are volumetric expansion of the concrete leading to deformation in the spillway gate built-in parts leading to gate operation problems. The proposed remedial and plunge pool enlargement works and modernisation of the monitoring equipment need to be implemented in the shortest possible time to guarantee continued dam safety.”
Sitali said the EIZ team of experts recommended that the immediate significant effects of Alkali aggregate reaction on the gates and associated hydro-mechanical works should be addressed to guarantee spillway operations, under varying conditions.

The concern comes in the wake of the mining activities taking place in the two countries-Zimbabwe and Zambia with the former relying on copper production as the country’s mainstay-representing 80% of the country’s Gross Domestic Product.

According to analysis, the Kariba Dam supplies 1,319 MW of electricity to parts of both Zambia (the Copperbelt) and Zimbabwe and generates 6,400 GW·h per annum.

Each country has its own power station on the north and south bank of the dam respectively. The south station belonging to Zimbabwe has been in operation since 1960 and has six generators of 125 MW capacities each for a total of 750 MW.

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