As rescue workers provide aid to Thailand, inundated with the worst floods in half a century, high waters have arrived within Bangkok, threatening evacuation centers and forcing the government to announce it is now in "crisis mode."

Prime Minister Yingluck Shinawatra announced inner Bangkok, especially areas near the Chao Phraya river, were at risk for flooding in a television broadcast on Tuesday evening. “If some of Bangkok’s protective flood walls are breached, Inner Bangkok could see anywhere from 10 to 150 cm [up to almost 5 feet] of water,” she said, asking residents to prepare to evacuate in the next couple of days.

The potential factors combining this week for Thailand’s already drenched capital have put the government on high alert. An estimated 4 billion cubic meters of water from draining from farm lands and higher elevated parts of Thailand are slated to reach the capital on Oct. 26, coinciding with a high tide on Oct. 28. On top of that, rain storms are expected to continue to drench Bangkok for the next three days.

Flood victims from all of the 33 severely affected provinces arrived by the truckload with their belongings and pets at the Don Muang airport in Bangkok Tuesday to seek refuge at an evacuation center there, but were met by muddy, rising water right at the airport’s doorstep.

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Amid flash flood warnings and floodwaters already more than a foot deep on the outskirts of the city, Prime Minister Yingluck declared a five-day holiday in Bangkok and 20 other provinces in a cabinet meeting that took place at a VIP terminal of the airport Tuesday morning. Don Muang airport also houses the Flood Relief Operations Center (FROC), the government’s flood relief and planning “war room,” an evacuee center, and a volunteer center.

The airport, which runs only domestic flights, has suspended all air traffic until Nov. 1 because of water on the runway.

Though no official statement has been issued for the airport, some 1,000 evacuees were urged to evacuate from to another center in Chonburi. A FROC spokesperson said they would be provided with transportation. “It is a wise decision to leave,” he said.

Outside Bangkok's city center, more than 100,000 people are living in about 1,700 government evacuation centers, which can handle as many as 800,000 people, reports Bloomberg.

Another evacuation center, Thammasat University in nearby Rangsit, received evacuees, but was later itself flooded. When center staff issued with an evacuation warning, some residents refused to leave.

Meanwhile, though the responsible ministries have promised there will be no problems with power and water supply, Bangkok store shelves are almost empty of bottled water and candles.

Royol Chitradon of the Hydro and Agro Informatics Institute says he believes the water management infrastructure has been neglected, and natural waterways have been blocked by the growth and placement of roads and cities. “Ultimately, the infrastructure has been poorly managed,” he told the Monitor.

The AFP reported that the US withdrew an aircraft carrier sent to help with relief efforts after receiving “mixed” messages from the government. A defense official in Washington told AFP, “There were two channels [in the Thai government]. One was saying ‘yes,’ and one was saying, ‘no.’”

Thai foreign ministry spokesperson Thani Thongpakdi issued a statement saying that the US had not been refused, but rather that the floods were not life-threatening and therefore there was no need for the US helicopters.

Specialists say it could take anywhere from four to six weeks for floodwaters to recede.