Durban, South Africa’s third-biggest city, started rationing water supplies to stave off a shortage.

Supplies to northern areas of the coastal city will be restricted for six hours a day with immediate effect, the eThekwini Municipality said in an e-mailed statement Friday.

The restriction is expected to intensify to in coming weeks to extend supply by the Hazelmere Dam for as long as possible until the start of the summer rains. Bulk supplier Umgeni Water said the dam level of 28% includes a 15% silt content.

“This means available water capacity is less than half the measured capacity,” Shami Harichunder, a spokesman for the utility, said by phone. “We’re in a desperate situation.”

Drought in eastern and central South Africa around the turn of the year, the worst since 1992, has slashed corn and sugar output and may trigger water shortages for homes and businesses. Weaker river flow also threatens water quality. South Africa is the 30th-driest nation on Earth, according to the government, which expects water demand to outstrip supply as early as 2025.

Water levels are decreasing at a rate of 1% every five days and Umgeni Water is implementing emergency-supply measures, Harichunder said.

About 25% of the Durban Chamber of Commerce and Industry’s members are affected by the water rationing, Justice Matarutse, the chamber’s policy and advocacy manager, said by phone.

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