The Metropolitan Waterworks Authority (MWA) (Thai: การประปานครหลวง) is a Thai state enterprise under the Ministry of Interior.
The MWA began operations on 16 August 1967 under the Metropolitan Waterworks Authority Act B.E. 2510 (1967) to serve potable water to Bangkok, Nonthaburi Province, and Samut Prakan Province. MWA's governor is Mr Thanasak Watanathana. The chairman of the MWA Board is Mr Chareon Passara.
In the reign of King Rama V, when Bangkok had a population of around 333,000, following the king's first visit to Europe in 1897, the king ordered the establishment of a Sanitary Department to provide water to the Bangkok populace. Many still used water from rivers or canals, frequently the source of epidemics. The new department made a survey and dug up a distributary canal of the Chao Phraya River at Sam Lae Sub-district in Pathum Thani Province to the north of Bangkok. Water was drawn though this canal into Bangkok to supply cleaner water.
In 1907, the king made a second visit to Europe. He found that most European countries produced clean, adequate water for their people. Returning to Thailand, he ordered the hiring of French experts to conduct a survey and make suggestions on water procurement for Bangkok. In 1909, the king ordered the Sanitary Department to dig and construct canals and install water pumps in order to deliver water to water treatment plants in the Sam Sen Sub-district. Pipes were installed underground to distribute water throughout the Bangkok area, at a cost of over four million baht and five years of construction. The king called the result "Bangkok Waterworks".
On 13 July 1909, the king ordered the Sanitary Department to treat water for use in Bangkok. The first water treatment plant was set up in 1914.
Demand for water in Bangkok increased rapidly, from 10,000 to 13,000 metres3 per day, most of which was consumed at numerous public water spigots. People in the suburbs of Bangkok, with no water supply, carried pots to take water from them, especially in the summer, when the waterworks increased production to full capacity of 28,800 m3 per day, sufficient for the population at the time. The government's emphasis on improving water supplies in Bangkok led to the merging of the Nonthaburi municipality water supply, Samut Prakan's water supply, and Thonburi's water supply with those of Bangkok Waterworks. A new organization called the "Metropolitan Waterworks Authority", a public enterprise under the Interior Ministry, began operations on 16 August 1967.
The MWA draws raw water from two sources: the Chao Phraya River at Ban Krachaeng Sub-district, Mueang Pathum Thani District, Pathum Thani Province and from the Mae Klong Dam in Tha Muang District, Kanchanaburi Province. The water is treated with lime, chlorine, alum, and polyelectrolyte at four water treatment plants—Bang Khen, Sam Sen, Thonburi, and Maha Sawat. MWA's treated water is distributed to its 2,226,707 customers in five regional service areas via 33,187 km of water pipes. The 2015 average tariff for residential customers was 10.5 baht per cubic metre. Total consumption in FY2015 was 1,406 million m3. At end-September 2015, the MWA employed 5,339 persons.
Charges for MWA water for residential users range from 8.50-14.45 baht per m3 depending on usage. These rates have evidently been unchanged since December 1999. MWA does not add waste water charges to water supply bills, despite clear evidence from international experience that this is best practice. Critics claim this exacerbates Thailand's water pollution problems for want of adequate funding.
MWA's fiscal year (FY) runs from 1 October to 30 September. In FY2015 (1 October 2014 – 30 September 2015) MWA reported total assets of 66,751 million baht, revenues of 19,917 million baht, and a net profit of 7,150 million baht.