By Nyasha Mutena
Lake Kariba’s water level continues to recede steadily and is at 481.55m as of September 1 2021, Zambezi River Authority has announced.
The world’s largest man-made lake and reservoir by volume, has receded by 0.61m, since the last update made on August 4 2021 when the recorded lake level was 482.16m.
Currently, the lake level is 6.05 meters above the Minimum Operating Level (MOL) of 475.50m.
In a statement, the Authority said the current level translates to 28.16 Billion Cubic Meters (BCM) or 43.45% of usable or live water.
Last year on the same date, the Lake level was lower at 480.48m with 22.94BCM or 35.40% of usable storage, with the water being only 4.98m above the Minimum Operating Level.
In account of that, the Authority highlighted that it maintained the 42 Billion Cubic Meters (BCM) combined water allocation for power generation operations at Kariba for 2021 after it was revised upwards from 30 BCM on 25th June 2021.
Another catchment, Chavuma is also receding, with a record of 154 cubic meters per second (m3/s) as of the 31st August 2021. On the same date last year, the flow was slightly higher at 161 m3/s.
In addition, the Zambezi River flows at the world tourist destination, the Victoria Falls, are also receding with a record of 482 m3/s as of the 31st August 2021. This is less than the 31st of August 2020 reading of 512m3/s. The recorded river flows are projected to also continue receding until the start of the 2021/2022 rainfall season.
The Authority is scheduled to undertake the next quarterly hydrological review at the end of September 2021, and this may result in either maintaining, increasing, or reducing the volume of water allocated for power generation operations at Kariba for the year 2021.
Weather experts and Meteorological Departments of Zambia and Zimbabwe, during the annual Southern Africa Climate Outlook Forum (SARCOF) which took place from 30 to 31 August 2021 predicted a normal to above normal rainfall outlook for the SADC region.
The Authority accordingly scheduled hydrological simulations that will inform decisions on the water to be allocated for power generation operations at Kariba for the year 2022. Meanwhile, the Authority stated that it continues to undertake the usual hydrological reviews for sustaining the reservoir operations at Kariba.
The bi-national organization is mandated to contribute to the economic, industrial, and social development of the Republics of Zambia and Zimbabwe by obtaining the greatest possible benefits from the natural advantages offered by the Zambezi River through the most economical and effective means of providing water for electricity generation plus other purposes which the contracting States may decide upon.
One of the ZRA’s utilities, Zimbabwe Power Company (ZPC) says water power generation utilities directly intake water from the lake into the station for power generation.
“These intakes were designed at a certain depth, about 13 metres below the maximum water level. They were not located at the bottom in order to avoid ingress of mud which would clogg the generation facilities. This means that only a certain amount of Lake Kariba water is accessible for power generation, and this is known as live water. If the water levels go below the water intake pipes there is no way to access water for power generation, thus, water below the intakes is referred to as dead water because it is unusable for power generation,” said ZPC.
The drop in water levels at Lake Kariba necessitated a reduction of water allocation to its utilities, ZPC and ZESCO, hence, reducing their generation capacities as a means to ensure electricity generation till the next rainy season.
Zimbabwe’s largest hydroelectric plant, Kariba Dam, will suspend output if water levels continue to recede.