Tap water produced by the Metropolitan Waterworks Authority (MWA) is slowly getting saltier as the Royal Irrigation Department (RID) decreases the discharge of water from its dams into the Chao Phraya River, but it should not be noticeable yet.
Media reports quoted MWA governor Thanasak Watanathana as saying the rate of discharge was being limited because of a water shortage and delayed rains. The situation affects not only water for agriculture, but also the MWA's production of tap water for about 10 million people.
The reduced discharge from the dams allows seawater to advance inland. The salinity level had already risen at the MWA's Sam Lae raw water intake station next to the Chao Phraya River in Muang district of Pathum Thani, north of Bangkok, he said.
The salinity level of the MWA's tap water stood at 0.2-0.3 milligrammes per litre. Consumers would start to sense the saltiness when the level rose to 0.5 mg/l.
Unless the amount of rainwater discharging into the the Chao Phraya River returns to normal in the next month, the tap water would become brackish, Mr Thanasak said. If this becomes likely, the MWA would advise each household to store at least 60 litres of tap water for consumption beforehand.
Since May 12, the MWA has reduced its production by 10% and distributed less tap water at night.
Also due to the water shortage, the Provincial Waterworks Authority has started to ration tap water in Phimai and Pak Thong Chai districts of Nakhon Ratchasima province, on Koh Phangan island of Surat Thani province, in Kaeng Khro and Nong Bua Daeng districts of Chaiyaphum, Kranuan district of Khon Kaen, Wichian Buri district of Phetchabun, Phai Sali and Tha Tako districts of Nakhon Sawan, and Lue Amnat district of Amnat Charoen.