Zimbabweans are being subjected to 19 hours of power cuts a day, because there is insufficient water in the Kariba dam to drive the nation’s main hydropower plant.

The worst outages since 2019 are wreaking havoc, causing snarl-ups in Harare, the capital, where most traffic lights are no longer working, and interrupting mobile phone services because batteries used to run base stations don’t have time to recharge. Supermarkets, restaurants and some other businesses rely on generators to keep operating, but they are unable to run them perpetually for an extended period.

“Kariba generates almost half of our power needs, which is why a reduction in its generation capacity immediately registers throughout our economy and in our lives,” Zimbabwean President Emmerson Mnangagwa wrote in his weekly column in state media on Sunday.

The level of usable water in Kariba, which is the world’s largest man-made reservoir and is tapped by both Zambia and Zimbabwe, stood at 4.1% as of Nov. 28, a record low, according to the Zambezi River Authority, which manages water supply for the two southern African nations.

Zimbabwe has used up its water allocation from Kariba this year and was drawing 200 MW of power from the dam’s hydropower plant on Monday, less than a fifth of the installed capacity it should be able to access, according to data on the Zimbabwe Power Company website.

“Kariba will not shut down completely,” Soda Zhemu, the energy minister, said in an emailed statement. The authorities plan to increase power imports from South Africa and Mozambique, and ramp up production from its antiquated coal-fired power stations in Hwange to at least 400 megawatts to help add capacity to the grid, he said.

Zambia will start rolling blackouts from Dec. 15 that will last for six hours at a stretch and only affect residential areas, Energy Minister Peter Kapala, told lawmakers on December 2.