Water Quality Index
In response to Member Countries’ concerns over potential water pollution and its trans-boundary implication, in 1985 MRC began a water quality monitoring programme in Lao PDR, Thailand and Viet Nam. Cambodia joined the programme in 1993. The current Water Quality Monitoring Network includes water quality monitoring at 48 permanent monitoring stations; of which 11 are in Lao PDR, 8 in Thailand, 19 in Cambodia and 10 in Viet Nam. Samples of surface water are taken from the river mid-stream every two months, i.e. six times a year starting from February. Member Countries may increase the sampling frequency, but this is not more 12 times a year. Water quality analysis is conducted in designated laboratories.
Based on a review of the scientific literature and a statistical analysis of the MRC data, a Water Quality Index has been designed based on a set of key water quality parameters. The Water Quality Index shows the pressure exerted by human activities on the water quality of the Mekong River. The Water Quality Index is calculated each year for 17 stations in the mainstream of the Mekong River from the Northern Lao PDR to the Mekong Delta.
Legend
- Class A - No Impact
- Class B - Slight Impact
- Class C - Impact
- Class D - Severe Impact
The map contains a marker at the location of the Water Quality Index monitoring stations, and the colour of the marker is based on the Water Quality Index class for 2008,
Click on a marker for more information on the station and to review the Water Quality Index class from 2000 to 2008.
Calculation of the Water Quality Index
Four parameters and their guideline values were selected to assess the “Human Impact” on water quality in the Mekong River: Dissolved Oxygen (DO), Ammonium (NH4), Chemical Oxygen Demand (COD) and Total Phosphorus (TP).
| Parameter | Value (mg/l) |
|---|---|
| Dissolved Oxygen | ≥ 6 |
| Ammonium | < 0.05 |
| Chemical Oxygen Demand | < 4 |
| Total Phosphorus | < 4 |
A simple scoring system was developed to calculate the Water Quality Index. On any given day of sampling, if DO, NH4, Chemical Oxygen Demand, and Total Phosphorus meet the guideline value, a score of 2 points is awarded per parameter. Otherwise the score is 0. The Water Quality Index value is calculated by dividing the total score by the maximum score possible, multiplied by 10. The Water Quality Index has four categories.
| Class | Score | |
|---|---|---|
| A | No Impact | 10 to 9.5 |
| B | Slight Impact | 9.5 to 8.5 |
| C | Impact | 8.5 to 7 |
| D | Severe Impact | < 7 |
For More Information
The MRC has published The Mekong River Report Card on Water Quality in 2010 and 2008 which are downloadable from the MRC Main Website Publications pages and also two Technical Paper Series publications.
- An Assessment of Water Quality in the Lower Mekong Basin (Technical Paper No. 19, 2008)
- Diagnostic study of water quality in the Lower Mekong Basin (Technical Paper No. 15, 2007)