The Metropolitan Waterworks Authority has urged Bangkokians to start stockpiling tap water now as higher levels of sea water are likely to affect production in the city's east this week.
HIGH AND DRY: A boy walks down the parched bank of Ban Chung canal in Ayutthaya’s Nakhon Luang district. The canal is drying up rapidly.
The salt water, which usually taints the Chao Phraya river in the dry season, is expected to reach the MWA's Sam Lae pumping station in Pathum Thani's Muang district by tomorrow, said MWA governor Thanasak Watanathana, referring to the forecast given by the Royal Navy's Hydrographic Department.
The pumping station feeds fresh water to the agency's tap water production facility for the eastern part of the capital.
With the exception of residents living in the Thon Buri area in western Bangkok, others need to store tap water while the quality still meets acceptable standards in order to have "normal tap water for consumption" until the problem passes, Mr Thanasak said.
The MWA has already encountered an intrusion earlier this month, causing officials to divert water from the Mae Klong river to the Chao Phraya basin.
The diversion was needed to maintain the quality of tap water.
Mr Thanasak earlier played down worry over the impact of the diversion. He said there was enough water in the Mae Klong river. Significant amounts of water have also been pushed into the Mae Klong River to feed the Chao Phraya River Basin through the Phraya Banlue, Thasarn Wangpla and Jorakhay Samphan canals.
The early intrusion this year resulted from drought that has decreased the amount of water in many parts of the Chao Phraya River.
According to deputy MWA governor Wisut Oppakhunthong, the agency currently has two main sources of raw water _ Mae Klong Dam in Kanchanaburi and the Chao Phraya River in Pathum Thani.
Raw water from Kanchanaburi goes to tap water production in Mahasawat canal. It serves people in Thon Buri and parts of Nonthaburi province.
Water quality in this area will not be affected by the salt water intrusion.
But the water quality in the Chao Phraya river must be closely monitored.
Recently officials have detected salt water in Ayutthaya's Bang Sai district, located to the north of Sam Lae pumping station in Pathum Thani, despite efforts by the Department of Royal Irrigation to prevent it.
Officials said they would need to stop pumping water from the Chao Phraya River if the level of salt water was high.
The MWA is trying its best to bring tap water quality into line with World Health Organisation standards.
Tests of water quality are conducted regularly to ensure people have clean water.
The result may sometimes show higher levels of salt in the tap water, however.
But Mr Wisut said in the MWA's latest statement that there was no serious danger to people's health.
They may only feel thirsty or have dry lips and mouths.
Last week, officials found high levels of chloride at Sam Lae of more than 0.25 grammes per litre.
It contacted the Department of Royal Irrigation to release fresh water at a higher rate until June.
The salt water intrusion will happen about twice a month, in line with the lunar gravitational pull.
According to the WHO, drinking water should not have chloride levels above 0.25 grammes per litre.