According to the agreement signed between the HKSAR Government and Guangdong Authorities, the Dongjiang water supplied to Hong Kong should conform to the national standard set out for Type II waters (applicable for the abstraction for human consumption in first class protection area) in the "Environmental Quality Standards for Surface Water GB3838-2002". The raw water after treatment by Hong Kong's water treatment works is suitable for drinking. The Guangdong Authorities have carried out the following measures in recent years so as to assure the quality of Dongjiang raw water transferred to Hong Kong :
Moved the intake of Dongjiang water upstream in 1998 where the water quality is better.
Commissioned the Bio-nitrification Plant at the Shenzhen Reservoir in early 1999.
Constructed and put into operation a dedicated aqueduct from the Dongjiang intake to Shenzhen Reservoir in late June 2003.
To enable the public in Hong Kong to understand the actual situation, the Department of Environmental Protection of Guangdong Province has regularly provided the water quality data for samples taken from the East Bank Section of Dongjiang's main stream upstream from the intake of Dongjiang water at Taiyuan Pumping Station. The data taken in 2009 is summarised in the following table.
Statistics on Water quality of Dongjiang's Main Stream in 2009 as Monitored at the East Bank Section
| Item | Temperature (oC) |
pH | Dissolved Oxygen |
Permanganate Index |
Chemical Oxygen Demand |
5-Day Biochemical Oxygen Demand (BOD5) |
Ammoniacal Nitrogen |
Total Phosphorus |
| January | 18.7 | 7.33 | 7.73 | 1.67 | 12 | 1.0 | 0.403 | 0.082 |
| March | 20.2 | 6.99 | 7.40 | 1.93 | 9 | 1.0 | 0.383 | 0.055 |
| May | 26.0 | 7.22 | 6.80 | 2.03 | 7 | 2.6 | 0.477 | 0.066 |
| July | 29.0 | 7.03 | 6.23 | 1.67 | 5 | 1.0 | 0.450 | 0.091 |
| September | 32.5 | 6.80 | 5.17 | 2.43 | 5 | 1.0 | 0.390 | 0.092 |
| November | 26.1 | 7.20 | 5.87 | 2.10 | 5 | 3.7 | 0.633 | 0.082 |
| Yearly Mean | 25.4 | 7.06 | 6.53 | 1.97 | 7 | 1.7 | 0.456 | 0.078 |
| GB3838-2002 Type II Standard for Surface Water |
- | 6 - 9 | >=6 | <=4 | <=15 | <=3 | <=0.5 | <=0.1 |
| Item | Copper | Zinc | Fluoride | Selenium | Arsenic | Mercury | Cadmium |
| January | 0.001 | 0.025 | 0.19 | 0.00277 | 0.009 | 0.00002 | 0.0005 |
| March | 0.001 | 0.025 | 0.26 | 0.00187 | 0.008 | 0.00002 | 0.0005 |
| May | 0.001 | 0.025 | 0.35 | 0.00090 | 0.004 | 0.00002 | 0.0005 |
| July | 0.004 | 0.025 | 0.22 | 0.00083 | 0.004 | 0.00002 | 0.0005 |
| September | 0.001 | 0.025 | 0.32 | 0.00030 | 0.004 | 0.00002 | 0.0005 |
| November | 0.014 | 0.025 | 0.26 | 0.00040 | 0.004 | 0.00002 | 0.0005 |
| Yearly Mean | 0.004 | 0.025 | 0.27 | 0.00118 | 0.006 | 0.00002 | 0.0005 |
| GB3838-2002 Type II Standard for Surface Water |
<=1.0 | <=1.0 | <=1.0 | <=0.01 | <=0.05 | <=0.00005 | <=0.005 |
| Item | Chromium (VI) |
Lead | Cyanide | Volatile Phenols |
Petroleum Hydrocarbons |
Anionic Surfactants |
Sulphides | Faecal Coliforms (no./L) |
| January | 0.002 | 0.005 | 0.002 | 0.001 | 0.017 | 0.02 | 0.002 | 759 |
| March | 0.002 | 0.005 | 0.002 | 0.001 | 0.023 | 0.02 | 0.002 | 700 |
| May | 0.002 | 0.005 | 0.003 | 0.001 | 0.017 | 0.02 | 0.002 | 653 |
| July | 0.002 | 0.005 | 0.002 | 0.001 | 0.027 | 0.02 | 0.002 | 790 |
| September | 0.002 | 0.005 | 0.002 | 0.001 | 0.030 | 0.04 | 0.002 | 985 |
| November | 0.002 | 0.005 | 0.002 | 0.001 | 0.013 | 0.02 | 0.002 | 759 |
| Yearly Mean | 0.002 | 0.005 | 0.002 | 0.001 | 0.021 | 0.02 | 0.002 | 768 |
| GB3838-2002 Type II Standard for Surface Water |
<=0.05 | <=0.01 | <=0.05 | <=0.002 | <=0.05 | <=0.2 | <=0.1 | <=2000 |
Note : Except pH and where specified, all units are in mg/L.