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Kariba Dam rehab underway

NANCY SIAME, Lusaka
THE Zambezi River Authority (ZRA) has finally submitted an environmental impact assessment report to the Zambia Environmental Management Agency (ZEMA) for the repair of the plunge pool and the spillway at Kariba Dam at a cost of over US$2.2 million.
The aim of the Kariba Dam rehabilitation works is to improve the stability of the plunge pool through reshaping its profile.
According to the report, the rehabilitation of the plunge pool will limit the preferential erosion towards the foundations of the dam along zones of weak rock.
Under the project, ZRA also aims to rehabilitate the six sluice gates of the spillway, enabling the ongoing use of the spillway function to manage the reservoir levels.
“The schedule will depend on the spillage duration governed by the specific hydrological conditions during the works,” the report read in part.
The preferred option is to allow a three-phase works schedule estimated to take about three and a half years to be completed which will involve on-site works to reshape the plunge pool, refurbish the spillway and the concrete surface of all sluices.
“The on-site works to refurbish the spillway will be performed after the plunge pool reshaping…The work needed within the sluices is associated with the refurbishment of the concrete surface of all sluices which have been distorted over the years due to an advanced alkali-silica reaction,” the report notes.
It notes that without functional sluices, the reservoir level cannot effectively be maintained to take into account the flood regime of the Zambezi River.
“Without the ability to release water from the reservoir, there is a danger of the reservoir being too full prior to a flood event, and the subsequent flood event causing over-topping of the dam wall which could lead to dam failure,” the report further reads.

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