(CNN) -- Thailand's devastating floodwaters are draining southward towards Bangkok Friday, and residents have been told to prepare for the worst when the spring high tide and a huge volume of water flowing down the Chao Phraya River merge over the next couple of days.
Workers in the city are rushing to shore up barriers and warnings have been posted for the northern suburbs.
"Between seven and eight billion cubic meters of water a day is being released from the Bhumibol Dam in the north of the country, which is heavily affecting provinces like Nahkon Sawan and Ayutthaya," government official Wim Rungwattanajinda told CNN.
"From that, about one to 1.2 billion cubic meters of water is reaching Bangkok every day."
So far, 283 people have been killed and two people are missing in Thailand, according to the government website Thaiflood.com. Some 61 of the country's 76 provinces have so far been affected, impacting more than eight million people.
More than 500,000 square kilometers -- an area the size of Spain -- are affected by the floods in Thailand, Cambodia, Vietnam and Laos, according to CNN meteorologist Jenny Harrison.
About 100 kilometers north of Bangkok, the UNESCO-listed historical city of Ayutthaya has now been submerged for 10 days, CNN's Paula Hancocks reports.
Shops in Ayutthaya are mostly flooded and closed, and people unable to leave their homes are waiting for help to arrive. Roads have become rivers, with people having to swim or use boats to get food and water.
"Doctors are patrolling the flooded areas in small boats and are making house-calls to residents to those incapable of moving," Hancocks says. "It's one of the worst hit areas in the country. Even if there are no more storms, one government estimate says it'll still take a month for the floodwaters to recede."
Temples and monuments are unable to keep the rising waters at bay, and there are fears that the longer the city's treasures are covered by water, the more likely it will be that the damage could be permanent.
"This is the worst flood in our historical site in 16 years," said Somsuda Leeyawanich, from the Thai Fine Arts Department. She said the water level in the park is almost three meters, compared to levels of around 80-90 centimeters during the floods of 1995.
"We are very concerned that if the site is under water for more than 30 days it may cause serious damage," she added. "The temples are over 400 years old."
Along with people and historical sites, animals are also are being severely affected by the floodwaters. Fifteen elephants, including seven mothers with babies and a nine-year-old known for its painting skills, are stranded on top of Ayutthaya's Royal Elephant Kraal.
The elephants climbed on top of the building last week and are going hungry now that food can only be brought in small quantities via rowing boats. Elephants can swim but it's feared the babies would drown in the floodwaters if they attempt to escape.
Meanwhile, the country's economy may be badly affected from the floods. Manufacturing areas just north of Bangkok have been particularly hard hit hard, including a Honda factory that has been submerged, ruining hundreds of cars.
The giant Rojana Industrial Park has also halted operations for the time being, director Amara Charoengitwattanagun told state-run news agency MCOT, and the facility may be further damaged if the flooding worsens. One plant in the park, Single Point Parts, evacuated all workers from the premises and built flood prevention embankments around its building.
"The Thai finance ministry says overall damage from the floods could be more than $2 billion, with the worst yet still possibly to come," Hancocks says.
CNN's Paula Hancocks and Kocha Olarn contributed to this report