During Rio de Janeiro's long summers of sticky subtropical heat, Viviane Vargas says she needs not one, not two, but three showers a day to feel clean.

The saleswoman is not alone: Surveys say Brazilians are the world's most frequent bathers, taking on average 12 showers a week, putting rub-a-dub-dub up there with soccer and Carnival as essentials of the culture.

But a historic drought that is making taps run dry across southeastern Brazil, particularly in South America's largest city of Sao Paulo, has people worried they might be asked to cut down on their beloved showers. While it may not be the most serious problem created by the drought, observers warn that restricting showers could spell trouble for political leaders.

"Showers are part of our roots as Brazilians. Not being able to shower in a country as hot as this, where hygiene is as culturally important as is it, well, it's enough to cause a revolt," said Renata Ashcar, co-author of the book "The Bath: Histories and Rituals," published in Brazil in 2006.

Brazil's populous southeastern region is in the throes of the worst drought in eight decades and reservoirs are at critical lows. Residents of Sao Paulo have faced water cuts for months, and that scenario is now looming for Rio de Janeiro.

Heavy rains in February and early March have helped reservoirs in the region recover somewhat — but they still are dangerously below normal levels. The Cantareira reservoir system that provides water for some 9 million people in metropolitan Sao Paulo, for instance, is at less than 13 percent capacity this week.

Under normal conditions, Brazilians are used to enjoying the world's largest freshwater supply. Residents in the southeast commonly hose down their sidewalks rather than sweep them and leave the water gushing from the tap as they brush their teeth.

The drought has sparked public information campaigns to discourage such habits, as well as car washing, and to urge people to adopt conservation steps such as collecting their shower water and re-using it to clean toilets and floors.

Vargas said she has begun to use water from the washing machine to water plants. But she's not giving up her routine of three showers a day — at least not yet.

"I can't live without them in this heat," she said.

The average high temperature in Rio during this Southern Hemisphere summer was 37 C (99 F) — making it the hottest big city in Brazil this year, according to the Climatempo meteorological institute. Throw in humidity routinely edging toward 80 percent, and it makes for a sticky mess that prompts people to shower in the morning and before going to bed at night.

Brazilians' showering frequency outpaces residents of nearly every other country, according to a survey published last year by Euromonitor, a London-based market researcher. The U.S., Spain, France and India all were around the world average, with just under seven showers a week.

"It isn't viewed well if you don't take a shower in Brazil, if you don't smell good," said Sissi Freeman, marketing director at the Brazilian soap and cosmetics company Granado.

Founded in Rio in 1870, the brand has grown into a nationwide chain that produces 9 million bars of soap a month. While Freeman said they haven't yet seen a dip in soap sales as a result of the drought, the company is "very concerned" and is developing products like wet wipes that might come to substitute showers in case rationing is imposed.

There have been frequent though small protests over the water issue, and historian Flavio Edler said it could get worse.

"If we were to have a severe restriction of water, there's no doubt we'd obviously see a social impact. ... It would be social chaos," said Edler, a researcher in the history of medicine and hygiene at the Casa de Oswaldo Cruz, an arm of one of Brazil's most respected health research facilities.

"I, myself, if one day I'm not able to shower, I feel profoundly bad all day long," he said.

___

Jenny Barchfield on Twitter: www.twitter.com/jennybarchfield