News / National
ZRA reduces water allocation at Kariba
20 Jul 2023 at 01:49hrs | Views
The Zambezi River Authority has reduced by a quarter the water allocation for power generation in the second half of the year owing to less than expected inflows from the upper Zambezi River catchment.
However, Zimbabwe should be able to cope since there is a huge increase in the generation at Hwange Power Station with the coming on stream of Units 7 and 8.
The new thermal capacity should make it possible for Hwange to handle the base load, with Kariba Power Station just coming in during peak periods and instantly increase ramp up production as the situation demands while staying within the allocated water ration. Both Kariba South and Kariba North were upgraded a few years ago to over 1 000MW, even though this could never be generated 24/7 since there was never the required inflows.
But both utilities, with a huge storage dam and the fact that a hydro unit can go from rest to flat out on the grid within a very few minutes, wanted to be able to handle the huge peaks with their stations going near flat out, and then cut back severely during the off-peak periods to keep the average within the ration.
As more solar comes onto the grid, the Kariba stations can be kept at very low output during the day with solar handling the non-coal load, and the daily water ration accumulating in the lake, and then as the sun sets the hydro stations can use that extra stored water.
ZRA had allocated 40 billion cubic metres as a standard in September 2022 on the strength of climate projections for the 2022/23 season of normal to above normal rainfall, which however, turned out to be normal to below normal in the upper catchment centred on eastern Angola.
To that end, ZRA has reduced water allocation for power generation to 30 billion cubic metres to shared equally between Zimbabwe Power Company on the South Bank and ZESCO of Zambia on the North Bank.
Flows upstream of the Zambezi River have started receding, consequently affecting inflows into Lake Kariba where levels peaked at slightly more than 20 billion cubic metres in storage of power generation.
ZRA chief executive Engineer Munyaradzi Munodawafa said the outcomes of the first quarter hydrological analysis influenced the decision to reduce the water allocation to the power utilities. Flows at Chavuma and Victoria Falls gauging stations are receding after peak flows in June.
"With the 2022/23 rainfall season having effectively ended in April 2023, the Kariba Catchment is no longer experiencing any rainfall activities.
"As per normal trend following the end of a rainfall season, flows of the Zambezi River and its tributaries are now receding and this downward trend is expected to continue until the commencement of the next rainfall season (2023/2024 rainfall season)," he said.
Lake levels rose from slightly above the minimum operating level of 475m in January 2023 to over 479 m recorded as the month of June ended giving storage of just 20,33 billion cubic metres, or 31,37 percent of what was there on the same date in 2022.
However, Zimbabwe should be able to cope since there is a huge increase in the generation at Hwange Power Station with the coming on stream of Units 7 and 8.
The new thermal capacity should make it possible for Hwange to handle the base load, with Kariba Power Station just coming in during peak periods and instantly increase ramp up production as the situation demands while staying within the allocated water ration. Both Kariba South and Kariba North were upgraded a few years ago to over 1 000MW, even though this could never be generated 24/7 since there was never the required inflows.
But both utilities, with a huge storage dam and the fact that a hydro unit can go from rest to flat out on the grid within a very few minutes, wanted to be able to handle the huge peaks with their stations going near flat out, and then cut back severely during the off-peak periods to keep the average within the ration.
As more solar comes onto the grid, the Kariba stations can be kept at very low output during the day with solar handling the non-coal load, and the daily water ration accumulating in the lake, and then as the sun sets the hydro stations can use that extra stored water.
ZRA had allocated 40 billion cubic metres as a standard in September 2022 on the strength of climate projections for the 2022/23 season of normal to above normal rainfall, which however, turned out to be normal to below normal in the upper catchment centred on eastern Angola.
To that end, ZRA has reduced water allocation for power generation to 30 billion cubic metres to shared equally between Zimbabwe Power Company on the South Bank and ZESCO of Zambia on the North Bank.
Flows upstream of the Zambezi River have started receding, consequently affecting inflows into Lake Kariba where levels peaked at slightly more than 20 billion cubic metres in storage of power generation.
ZRA chief executive Engineer Munyaradzi Munodawafa said the outcomes of the first quarter hydrological analysis influenced the decision to reduce the water allocation to the power utilities. Flows at Chavuma and Victoria Falls gauging stations are receding after peak flows in June.
"With the 2022/23 rainfall season having effectively ended in April 2023, the Kariba Catchment is no longer experiencing any rainfall activities.
"As per normal trend following the end of a rainfall season, flows of the Zambezi River and its tributaries are now receding and this downward trend is expected to continue until the commencement of the next rainfall season (2023/2024 rainfall season)," he said.
Lake levels rose from slightly above the minimum operating level of 475m in January 2023 to over 479 m recorded as the month of June ended giving storage of just 20,33 billion cubic metres, or 31,37 percent of what was there on the same date in 2022.
Source - The Herald
