Binational catchment authority, the Zambezi River Authority (ZRA) in a June 1 update on the state of the Kariba dam at the end of the rainy season said it has predominantly maintained the allocation of 23-billion cubic metres of water to power uitilities Zesco, in Zambia, and the Zimbabwe Power Company.
The authority plans to ensure the continued availability of water for power generation at the dam for the remaining months of this year and beyond.
"The lake level receded for the most part of the first quarter of 2020 with the obtaining lake levels being the lowest on record (with the only exception to this low lake level being the lake levels recorded during the 1995/6 drought period). The receding lake levels were mainly caused by the delayed onset of the 2019/20 rainfall season, which only commenced in January instead of October 2019 as projected by both local and regional weather experts and meteorological authorities, coupled by poor rainfall run-off which saw a delayed increase in the Zambezi River flows in the Kariba catchment," ZRA CE and engineer Munyaradzi Munodawafa said.
However, the lake level later rose by 3.13 m between March 27 and May 27 following increased rainfall activity and associated run-off, especially in the upper Kariba catchment. The lake level should have been, by then, no less than 8 m above the minimum operating level (MOL), but was only just over 5 m above the MOL by May 27, he pointed out.
As of May 27, the recorded lake level was 480.77 m, signifying 37.6% live storage or 24.40-billion cubic metres of stored usable water, with the lake being 5.27 m above the MOL of 475.50 m.
The ZRA also provided insight into readings from two of its gauging stations – Chavuma and Victoria Falls.
In March, the Zambezi river flows as measured at Chavuma had risen from 236 m3/s recorded at the start of January to a peak of 5 006 m3/s recorded in February. This recession in river flows continued up to mid-March, when the levels started rising again.
This second increase in flows, which is characteristic of Chavuma gauging station, continued up to April 6 when the river flows reached a second peak of 5 825 m3/s before gradually receding to the 776 m3/s flow recorded on May 27. The flow recorded on May 27, 2019, was 239 m3/s.
"The recorded flow at Chavuma on May 27 was therefore 225% higher when compared with the flow recorded on the same date last year. Further, the river flow at Chavuma continued to trend above the long-term average flow for the Chavuma gauging station of 482 m3/s," said Munodawafa.
Similarly, the Zambezi river flows recorded at Victoria Falls rose from 349 m3/s at the start of January to a peak of 4 289 m3/s on May 3.
The last time such high flows were attained at Victoria Falls was a decade ago, during the 2009/10 rainfall season, said Munodawafa.
The second upswing in flows at Victoria Falls started mid-April, mimicking the double peak at Chavuma four weeks later, this being the normal travel time of flood waters between Chavuma and Victoria Falls.
Following the peak in flows at Victoria Falls of just over 4 300 m3/s, the flows at Victoria Falls are now equally in recession with recorded flow of 3 355 m3/s on May 27.
"Last year on the same date, the recorded flow at Victoria Falls was 1 117 m3/s. Therefore, this year’s flow recorded on May 27 at Victoria Falls represents an increase of 200% when compared to last year's flow on the same date. Further, the recorded flow on May 27 is 57% higher than the long-term average river flow for Victoria Falls."
The ZRA continues to monitor the hydrological situation in the Kariba Catchment and water levels at the Kariba dam.