We would like to thank Vandana Marino for expressing her concern about the quality of Dongjiang water and Hong Kong's water supply in her letter ("We must know more about pollution levels", August 30).
The Water Supplies Department monitors the quality of Dongjiang water and has put in place measures to safeguard the quality of Hong Kong's drinking water.
The department routinely monitors the Dongjiang supply received at Muk Wu pumping station around the clock through its real-time online water quality monitoring systems. Regular samples are also taken for laboratory testing at Muk Wu and at Hong Kong's water treatment works.
According to our quality monitoring results, the quality of Dongjiang water supplied to Hong Kong remains stable and good.
During the period from April 1 last year to March 31 this year, the results show that the quality of this water complied fully with the Type II standard under the national "Environmental Standards for Surface Water", which is suitable for use in the municipal water supply.
Furthermore, a notification system has been established between the department and the Guangdong authorities. In the event of any incident that affects the quality of the water, the Guangdong authorities will inform the department immediately.
In response, we will liaise closely with Guangdong and take any action necessary to safeguard the quality of the water supply.
In addition, all raw water including Dongjiang water and rainwater collected from local catchments undergoes rigorous treatment and disinfection processes at Hong Kong's treatment works.
These treatment processes remove impurities present in the raw water and ensure that our treated supply is clean, wholesome and free from pathogenic bacteria.
The quality of treated water in Hong Kong complies fully with the World Health Organisation's "Guidelines for drinking-water quality".
For the information of interested readers, the department publishes its monitoring data on Dongjiang water and drinking water in Hong Kong on its website (http://www.wsd.gov.hk/en/water_resources/water_quality/water_quality_monitoring_data/index.html).
Gabriel Pang, senior engineer/public relations, Water Supplies Department