More than 30 percent of the city’s treated water is estimated to be lost to leaks and pilfering. In a statement, the water utility said it was seeking to reduce leaks. It has been offering discounts to reduce consumption, while starting to impose steep fines this month on high water use.

Outright rationing — in which service would be cut entirely for certain periods, not just reduced — is “still under discussion and study,” said Sabesp, the water utility, after rains in recent weeks slightly raised reservoir levels. But for people already experiencing what they describe as de facto rationing, the position of the authorities has been perplexing, at best.

“I feel hatred, hatred of the governor and of Sabesp,” said Márcia Oliani, 54, the finance manager of an art gallery who endured six days without water in her apartment. “I’d like to take them out and set fire to them. They completely failed to warn us, and have just continued to lie about this throughout.”

Water specialists warn that the crisis could still be in its early stages, meaning that the shortages in São Paulo, Brazil’s economic capital, could hamper efforts to strengthen a sluggish national economy grappling with low prices for the commodities Brazil exports.

“They haven’t hit the worst of it yet if they’re not trucking in water in large amounts,” said Steven Solomon, the author of “Water: The Epic Struggle for Wealth, Power and Civilization,” comparing the crisis with the situation in cities in India and Pakistan where residents go foraging for water or buy it on the black market from truck-size tankers.

In a country where abundant water is a source of national pride, where crystal orbs containing the water from more than 15 Brazilian rivers have been displayed in the grand Ipiranga museum here, the crisis has some questioning how Brazil’s mighty global city arrived at this point.

Ignácio de Loyola Brandão, a writer whose 1981 novel, “And Still the Earth,” imagined a São Paulo grappling with ecological degradation and chronic water shortages, told reporters that he was not surprised at its water problems, citing the reluctance of many households to curb their own water consumption and what he called the nonchalance with which many people in Brazil treat scandals or natural disasters.

“The majority doesn’t get indignant with anything,” he said, “as if we’re comfortably strolling toward our own demise.”