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Depleted Kariba water level cripples power generation

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THE water level at Kariba Dam continues dropping, affecting electricity generation, with inflows expected to make a difference in the first quarter of the 2023 rainy season, the Zambezi River Authority (ZRA) has said.

NATHAN GUMA

The ZRA is a bi-national organisation mandated by the governments of Zambia and Zimbabwe to sustainably harness the hydropower potential offered by the trans-boundary waters of the Zambezi River.

On 1 November this year, the ZRA recorded lake levels of 476.85 metres with 6.05 billion cubic metres (BCM) stored usable water or 9.32% of live storage, placing it 1.32 metres above the minimum operating level of 475.5 metres, said Munyaradzi Munodawafa, the ZRA chief executive officer, in a statement.

The level fell from 479.97 metres with a 20.47 BCM and water being at 4.47 metres above the minimum operating level recorded in the same period last year. The ZRA has 14 gauging stations located within the Kariba catchment area, among them the Chavuma and Victoria Falls gauging stations which are key in the monitoring of inflows into Lake Kariba. Chavuma recorded a drop in water flows during the last quarter of the 2021/2022 season.

 Despite the decrease, the ZRA says lake levels are likely to rise should flows recorded at the station be sustained.

“The Zambezi River flows recorded at Chavuma receded between June 2022 and end of October 2022. At the end of October 2022, the flows receded to 60 cubic metres per second. However, the catchment around Chavuma has recorded some rainfall activity leading to a slight increase in the recorded flow,” said the ZRA.

While rainfall increased the water flow to 63 m³/s, the total is still falling short of 95m³/s recorded in the corresponding period last year.

The ZRA has embarked on the water allocation process to cater for electricity generation at the Zimbabwean and Zambian hydroelectric power stations.

 The Southern Africa Regional Climate Outlook Forum downscaled the 2022-23 rainfall season prediction by Zimbabwe and Zambia at its 26th meeting of regional weather experts that took place at the end of August 2022.

 The two countries had predicted a normal to above normal rainfall season for the Sadc region, including the Kariba catchment zone.

“The Authority (ZRA) accordingly undertook hydrological simulation using the normal to above normal rainfall projections for the upcoming 2022/23 season and allocated 40 BCM of water to cater for the power generation operations at Kariba for 2023.

 “The BCM water allocation will be shared equally between Zambia Electricity Supply Corporation Limited (Zesco) and Zimbabwe Power Company (ZPC) for their power generation operations at Kariba North Bank Power Station and South Bank Power Station respectively,” reads the statement.

Zimbabwe has been reeling under power outages, even as the Zimbabwe Electricity Supply Authority Holdings continually hikes tariffs. Zambia’s end, called the Kariba North Bank Power Station, has an installed capacity to generate 1 080 megawatts (MW) while Zimbabwe’s end, the Kariba South Bank Power Station, has 1050MW installed capacity.

To ramp up power production, the ZRA has been implementing the Kariba Dam Rehabilitation Project (KDRP) which involves reshaping the plunge pool and refurbishing the six spillway gates to ensure long-term reliability of Kariba Dam.

 “It is worth noting that the water levels currently obtaining at Kariba Dam are favourable to the smooth implementation of the rehabilitation works.

 “In this regard, ZRA will continue to closely monitor and optimise the water allocation for power generation to ensure uninterrupted implementation of the KDRP works together with power generation operations, while avoiding the need for spilling which has potential to halt the works. “The ZRA 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,” read the statement.

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