Levels at the dam, which produces a combined 1 625MW of power on both the south and north banks, serving Zimbabwe and neighbours Zambia respectively, were earlier projected to be less, but gained significantly after unexpected floods upstream of the Zambezi River catchment.
At this stage last year, levels were around 28,32 percent, having started the decline at the beginning of June. In terms of power generation, Kariba was designed to operate at between 475,50m and 488,50m (with 0,70m freeboard).
In its latest update, Zambezi River Authority (ZRA) noted the four-day stagnation before the current decline.
“The Lake level has continued rising steadily, stagnating, and recording a first drop at the close of the period under review at 481,23m (41,04 percent usable storage) on 25th June 2020. Last year on the same date, the Lake level was at 479,52m (28,32 percent usable storage),” said ZRA in an update.
Usable storage is the water in the top 13m of a full lake that is the water above the inlets to the two power stations. There is a lot more water below the minimum usable level suitable for recreational activities and contains fish, but it cannot be used to generate electricity.
Most of the water in the lake comes from run-off in south-east Angola and rainfall in north-east Zambia. ZRA has marginally increased water allocation for power generation after initially putting a cap at 22 billion cubic metres for the year which will see the two stations producing a total of 500MW.