| Water class | % Na | % during dry season | % during wet season |
| Excellent | <20 | - | - |
| Good | 20 - 40 | 10% | 60% |
| Permissible | 40 - 60 | 60% | 30% |
| Doubtful | 60 - 80 | 20% | 10% |
| Unsuitable | >80 | 10% | - |