Zambia will start rationing electricity supply to domestic consumers from December 15 after a big drop in water levels in Lake Kariba threatening hydropower generation, energy minister Peter Kapala said on Friday.

Water levels in the lake have dropped to 4.1% of usable storage for the Kariba North Bank power station in Zambia and Kariba South Bank on the Zimbabwean side of the lake, Kapala told parliament.

“The low water level situation in Lake Kariba threatens power generation from both hydropower stations,” Kapala said.

Water levels in the lake have fallen due to reduced inflows from the Zambezi River and its tributaries and heavy use by power generation companies in Zambia and Zimbabwe.

Hydropower contributes more than 75% of Zambia's power generation.

Kapala said it was projected that if the current water utilisation continued, the remaining water for power generation would not be enough for power generation from mid-December.

To avoid a complete shutdown of the two power stations, the Zambezi River Authority told Zimbabwe to cut generation to a maximum 300MW and Zambia to a maximum 800MW, Kapala said.

“We anticipate this will translate into a load-management regime starting on December 15 of up to six hours daily,” Kapala said.

The Kariba North Bank station has an installed capacity of 1,080MW, while the South Bank station in Zimbabwe has a capacity of 1,050MW.

The two countries jointly manage the water in the lake through the Zambezi River Authority.