South America's biggest and wealthiest city may run out of water in two weeks if it doesn't rain soon. São Paulo, a Brazilian megacity of 20 million people, is suffering its worst drought in at least 80 years, with key reservoirs that supply the city dried up after an unusually dry year.

sao paulo drought
A vehicle drives along state highway SP-065 over the dry bed of the Atibainha dam, part of the system that provides most of the potable water to Greater Sao PauloReuters
sao paulo drought
A man stands in a crack on the dried-up bed of the Atibainha dam in Nazare PaulistaReuters

The severity of the situation in recent weeks has led government leaders to finally admit Brazil's financial powerhouse is on the brink of a catastrophe.

São Paulo residents should brace for a "collapse like we've never seen before" if the drought continues, warned Vicente Andreu, president of Brazil's Water Regulatory Agency.

Dilma Pena, chief executive officer of Sabesp, the state-owned water utility that serves the city, warned that São Paulo only has about two weeks of drinking water supplies left.

The Cantareira system, the main water reservoir feeding the region, dropped to just 3.4% of its capacity on 21 October, according to Sabesp.

The fall in the water level has exposed dozens of old cars dumped into the reservoir over the years, probably after being stolen.

sao paulo drought
Cars that the police suspect were stolen and dumped in the lake behind the Jaguari dam appear as the lake dries up due to a prolonged drought in Braganca Paulista, Sao Paulo stateReuters
sao paulo drought
A boat sits on the nearly dry lake bed behind the Nazare Paulista dam, part of the Cantareira water systemReuters
sao paulo drought
Footprints of a capybara are seen on the cracked bed of the Jaguari dam, part of the Cantareira water supply system, in Joanopollis, 136km (77 miles) from Sao PauloReuters
sao paulo drought
A Sao Paulo state worker stands next to water markers at Jaguari dam, 100km from Sao PauloReuters
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A view of the Jaguari dam station, part of the Cantareira reservoir, in Braganca Paulista, Sao Paulo stateReuters

Water pressure is reduced at night and people who cut back on use by 20% receive deductions in their monthly water bill. In some neighbourhoods, residents say water is cut for a few hours or days at a time.

The Estado de S.Paulo newspaper reported that the drought has affected close to 14 million people in 68 cities in the state. Almost 40 of these cities have started rationing water. Some of them receive water once every three days.

sao paulo drought
A resident fills water bottles from a pipe as the eight-month rationing of water continues as a result of a record drought, in ItuReuters
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Residents of Itu in Sao Paulo state receive water from public taps due to rationing in their homes as a result of a record droughtReuters
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A homeless man bathes in a sewage pipe that flows into the Tiete River in Sao PauloGetty
sao paulo drought
Maria das Gracas, 40, washes her plates from a improvised tap as water rationing continues in ItuReuters
sao paulo drought
The owner of a theatre in Sao Paulo stores water in a bucket, as the supply is switched off at nightGetty
sao paulo drought
Residents of Itu, in the region of Sao Paulo state that depends on the Cantareira water system, block a road during a protest against water rationingReuters
sao paulo drought
Monica Domingues stands with her children dressed in bathrobes and shower caps during a protest over the rationing of water, outside City Hall in ItuReuters

Sabesp, however, has assured customers that São Paulo won't run out of water, even though the main reservoir is nearly dry. A spokesman said Cantareira still has 40 billion litres of water thanks to emergency pumping below its flood gates. A second emergency pumping system will soon be ready and will provide an additional 106 billion litres of water to the Cantareira reservoir.

São Paulo State Governor Geraldo Alckmin said water from five other reservoirs in the city's metropolitan area is also being pumped into Cantareira.

One of the causes of the crisis may be more than 2,000km away, in the growing deforested areas in the Amazon region.

Antonio Nobre, a leading climate scientist at INPE, Brazil's National Space Research Institute, said: "Humidity that comes from the Amazon in the form of vapour clouds - what we call 'flying rivers' - has dropped dramatically, contributing to this devastating situation we are living today."

The changes, he said, are "all because of deforestation".