| Water quality classifications: WQI, Hardness, SAR, USSL, PI, MAR, RSC and KR indices, Douala | ||||||
| Class | Values | Quality | Wet | Dry | ||
| No | % | No | % | |||
| WQI Classification | ||||||
| 1 | 0 - 25 | Excellent | 20 | 100 | 12 | 60 |
| 2 | 26 - 50 | Good | 0 | 0 | 4 | 20 |
| 3 | 51 - 75 | Poor | 0 | 0 | 3 | 15 |
| 4 | 76 - 100 | Very poor | 0 | 0 | 1 | 5 |
| Hardness Classification | ||||||
| 1 | 0 - 75 | Soft | 12 | 60 | 3 | 15 |
| 2 | 76 - 150 | Moderately Hard | 4 | 20 | 11 | 55 |
| 3 | 151 - 300 | Hard | 4 | 20 | 3 | 15 |
| 4 | >300 | Very Hard | 0 | 0 | 3 | 15 |
| SAR Classification | ||||||
| S1 | <10 | Excellent | 20 | 100 | 20 | 100 |
| USSL Classification | ||||||
| C1 | 101 - 250 | Very Good | 3 | 15 | 9 | 45 |
| C2 | 251 - 750 | Good | 16 | 80 | 10 | 50 |
| C3 | 751 - 2250 | Doubtful | 1 | 5 | 1 | 5 |
| PI Classification | ||||||
| Class I | >75 | Excellent | 2 | 10 | 4 | 20 |
| Class II | 50 - 75 | Good | 13 | 65 | 16 | 80 |
| Class III | 25 | Unsuitable | 5 | 25 | - | - |
| MAR Classification | ||||||
| 1 | <50 | Suitable | 9 | 45 | 8 | 40 |
| 2 | >50 | Unsuitable | 11 | 55 | 12 | 60 |
|
|
|
|
|
|
|
|
| RSC Classification | ||||||
| 1 | <1.25 | Good | 20 | 100 | 20 | 100 |
| KR Classification | ||||||
| 1 | <1 | Suitable | 20 | 100 | 20 | 100 |