Water levels drop at Kariba dam

The Zambezi River Authority says reduced water levels in Lake Kariba were under control as it seeks to optimise power generation and progress at the Kariba Dam rehabilitation project.

While levels have dropped by more than 70 percent over the 2021 levels and are trending towards record lows, ZRA said it was monitoring the situation.

ZRA has assured Zimbabwe and Zambia power users that the allocated water for power generation to Zesa and Zesco would be maintained and only reviewed when hydrological conditions deteriorate to unsustainable levels.

While the decline is consistent with trends during this time of the year, levels have dropped rapidly and rains in the lake catchment area could reverse the trend.

A glimmer of hope is also emerging from the upper Zambezi River where flows are beginning to increase at Chavuma and Victoria Falls gauging stations.

However, the impact of the flows on water levels in the Lake will only begin to be felt in the first quarter of 2023 owing to the two-month time lag it takes for the flows to reach the lake.

Levels have receded to 6,04 billion cubic metres (BCM), dropping to within one and half metres of usable water as of November 1.

On the same day in 2021, the reservoir had 20,47BCM which was 4,47 metres above the minimum operating level and 8 metres below the maximum level.

ZRA chief executive Engineer Munyaradzi Munodawafa said adjustments to the 40BCM of water allocated to Zimbabwean and Zambian power utilities were subject to late onset of the rains.

The Southern African Regional Climate Outlook Forum (SARCOF-26), Zimbabwean and Zambian meteorological departments have forecast normal to above normal rains for the region.

"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," said Eng Munodawafa.

While power users may be edgy on the likely impact of falling water levels, the Kariba Dam Rehabilitation Project is progressing well as reshaping of the plunge pool and refurbishment of the flood gates is best done when levels are low.

Eng Munodawafa said low water levels ensured that there would not be any need to open the spillway gates which would jeopardise the ongoing works.

"It is worth noting that the water levels currently obtaining at Kariba are favourable to the smooth implementation of the rehabilitation works," he said.

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

According to hydrological simulations lake levels would start rising in the first quarter of 2023.

"However, the catchment around Chavuma has now recorded some rainfall activity leading to a slight increase in the recorded flow," said Eng Munodawafa.

"The recorded flow on 1st November 2022 increased to 63m3/s. On 1st November 2021, the flows were slightly higher at 95 m3/s."

All indicators at Chavuma and Victoria Falls gauging stations show that flows upstream of the Zambezi River were significantly lower compared to the 2021 season.

Flows at Victoria falls have slowed to 238 cubic metres (m3/s) on November 1, 2022 compared to 294 m3/s on the same day the previous season.

"However, with the 2022/2023 rainfall season activity now recorded at Chavuma which is located upstream of Victoria Falls, the flows at Victoria falls are also expected to start increasing by the beginning of the first quarter of 2023," said Eng Munodawafa.