- Kariba Dam’s water level ended last year at its lowest in 23 years, but recent data from three major river flow stations along the Zambezi River, show the encouraging trend that water flow towards the giant lake rose exponentially in December last year.
INFLOWS into Kariba Dam, the largest inland man-made dam in the world, have increased exponentially since December following heavy rains in the catchment area, bringing relief to authorities that hydro power output from the dam will soon also improve.
Kariba Dam is Zimbabwe’s largest power station, with capacity to produce 1 050MW, but is currently generating only 200MW due to critically low water levels following the drought experienced in the catchment area of the dam’s main feeder river.
Kariba Dam’s water level ended last year at its lowest in 23 years, but recent data from three major river flow stations along the Zambezi River, show the encouraging trend that water flow towards the giant lake rose exponentially in December last year.
While Kariba Dam is designed to operate at about 485 metres (water level) when full, its water level had dropped substantially to about 476 metres as at December 27, 2019 compared to 482 metres at the same time in December the previous year.
Live water is water above 475 metres below which the dam cannot be used for power generation, as this poses risk of exposing inlet valves to dangerous weather elements.
It is also critically important to avoid depleting Kariba Dam since the reservoir would require at least three good rainy seasons to fill it up again without using it to generate electricity in the event that it drains out. Even when not used for power generation, the dam must still have water for fishing and recreational activities.
Data gathered by the Zambezi River Authority, which administers the dam and the Zambezi River on behalf of the Zimbabwean and Zambian governments, shows that the amount of water that passed through major water flow stations at Victoria Falls, Chavuma, Nana’s Farm and Ngonye has increased substantially.
“Flows at Ngonye increased due to sporadic rainfall activities being recorded around the catchment, closing the week at 426 cubic metres per second on 27th December 2019, while last year’s flow on the same date was 295 cubic metres per second.
“The Zambezi River flows through Nana’s Farm station have been increasing due to records of rainfall activities on the catchment, closing the week under review at 362 cubic metres per second on 27th December 2019. The flow observed on the same date last year was 293 cubic metres per second,” ZRA said.
At Chavuma water flow steadily increased and closed the week under review at 213 cubic metres per second on the same date in December last year, while the flow observed at the same point last year on the same date was 127 cubic metres per second. The same pattern has been observed at Victoria Falls.
While rainfall activity around the catchment areas around water flow measuring points has increased inflows going into the lake, only 20 percent of water that comes from catchment areas in Zimbabwe makes up the water that flows into the Kariba Dam.
Zimbabwe requires about 1 800MW at peak period of demand for power, but struggles to even provide half of this from its domestic production facilities, with only two of its plants — Kariba and Hwange — still able to generate tangible amounts of power.
Because of the low lake water level Kariba cannot be used to full capacity despite having its capacity upgraded to current rated capacity after installation of two additional generators from the previous 750MW.
ZRA determines the amount of water that can be used for electricity.