The lake levels of the Kariba dam are in recession, recording a water level of 476.85 m – 1.35 m above the minimum operating level of 475.50 m – with 6.04-billion cubic metres of stored usable water, or 9.32% of live storage.
This as the region awaits the onset of the rainfall season, after the 2021/22 rainfall season ended in mid-2022, leading to reduced river flows.
At the same time last year, the level registered at 479.97 m with 20.47-billion cubic metres, or 31.59%, of usable live storage, and 4.47 m above the minimum operating level.
The Kariba Lake is designed to operate between levels 475.50 m and 488.50 m, with 0.70 m freeboard for hydropower generation.
The Lake level has been decreasing steadily on account of low inflows from the mainstream Zambezi river.
In its fourth update for the year on the water situation in the Kariba catchment and the lake levels at Kariba dam, the Zambezi River Authority (ZRA) said that the hydrological pattern during the last quarter of each year traditionally records reduced river flows.
However, lake levels are expected to start rising in the first quarter of 2023, if the flows recorded at Chavuma are sustained.
The Zambezi river flows recorded at Chavuma receded between June and the end of October to 60 m3/s, before rainfall activity increased the recorded flow to 63 m3/s on November 1. In the prior year, on November 1, 2021, the flows were higher at 95 m3/s.
The Zambezi river flows monitored at Victoria Falls were also receding owing to the close of the 2021/22 rainfall season.
The recorded flow was at 238 m3/s on November 1, compared with 294 m3/s reported in the same period the year before.
However, with the 2022/23 rainfall season activity now recorded at Chavuma, which is upstream of Victoria Falls, this is expected to start increasing during the first quarter of 2023.
Meanwhile, with a predicted normal to above normal 2022/23 rainy season outlook for the South African Development Community region, including the Kariba catchment, the ZRA allocated 40-billion cubic metres of water for the power generation operations at Kariba for 2023.
This will be shared equally between Zesco and Zimbabwe Power Company for the power generation operations at Kariba North Bank Power Station and Kariba South Bank Power Station respectively.
The authority will continue to monitor the hydrological outlook in the Kariba catchment and, where necessary, make adjustments to this water allocation to sustain reservoir operations at Kariba.