ZAMBEZI River Authority says it does not expect water levels in Lake Kariba to recover to maximum power generation capacity until 2020.
And ZRA says delayed rehabilitation of the plunge pool poses a real risk of the Kariba dam wall collapsing.
ZRA says it was going to restrict water for power generation at Lake Kariba this year to only 30 billion cubic metres from the installed capacity of 65 billion cubic metres, a move expected to see a continued reduction in power generation by both Zesco and Zimbabwe Electricity Supply Authority, (ZESA), resulting in continued load shedding in the two countries.
ZRA hydrology technician Bob Mwangala said it would take at least three years of normal-to-above rainfall patterns for the lake to harvest the 65 billion cubic metres of water required for maximum hydropower generation by the two countries.
He explained that water inflows into Lake Kariba had in the last three years drastically fallen owing to reduced rainfall activities in its catchment area in North Western and Western provinces.
“From the hydrological simulations that we have done for Lake Kariba to reach its normal levels, we will take at least three consecutive good hydrological years given our hydrological situation and assuming the status quo where we anticipate above average inflows remain the same up to March,” Mwangala said.
He said power generation at Kariba would remain suppressed both on the Zambian and Zimbabwean side.
“In 2016, we allocated 20 billion cubic metres of water available to each utility [Zesco and ZESA],” Mwangala said. “In 2017, looking at the current rainfall forecast that we have received, we ended up allocating about 30 billion cubic metres of water available to the two utilities.”
He explained that although the whole of the Southern Africa region had received normal-to-above normal rainfall, the Lake Kariba catchment area remained low in water contribution to the lake.
On Tuesday, the river authority announced that it had picked French engineering firm Razel-Bec to rehabilitate and reshape the plunge pool of the crucial Kariba Dam to prevent the dam wall from cracking.
According to an official at Zambezi River Authority, a bi-national company to manage the iconic dam on behalf of the two countries, the reshaping of the plunge pool and rehabilitation of the spillway should take up to five years at the cost of US $294 million.
Kariba Dam safety manager Kozanai Gurukumba said expanding of the plunge pool should be completed by end of the 2020 while rehabilitation of the spillway to contain swelling in the dam wall was expected to be done by 2022.
“It has taken a while in terms of procurement process but the contract is now official and tomorrow [Tuesday] the [Zambian] Minister of Finance [Felix Mutati] and the European Union will officially sign the contract and we expect the contractor Razel Bec of France to take possession of the site by mid next month,” Gurukumba told journalists in Siavonga.
He said the rehabilitation works would be funded through a cocktail of grants and loans from funders who included the European Union, the World Bank, African Development Bank and the Embassy of Sweden.
Gurukumba said over the years, the plunge pool had been eroded by over 80 metres, causing cracks to start going the direction of the dam’s foundation.
“The idea of reshaping and increasing the plunge pool is to make it bigger to absorb more energy from the falling water so that we don’t threaten the dam wall,” Gurukumba said.
He said 300, 000 cubic metres of rock material would be excavated to create for more space for falling water.
“More or less, you are replacing it by water body of that volume and by so doing, you are reducing the threat of the undercutting of the foundation,” said Gurukumba.
ZRA said the process to pick a contractor to rehabilitate the spill-way should be completed by the end of this year for works to start in the first quarter of next year.