| Water quality parameters | Range applicable | Equation |
| DO (Percent saturation) | 0% - 40% saturation | IDO = 0.18 + 0.66 × (% saturation DO) |
| 40% - 100% saturation | IDO = −13.55 + 1.17 × (% saturation DO) | |
| 100% - 140% saturation | IDO = 163.34 − 0.62 × (% saturation DO) | |
| BOD (mg/l) | 0 - 10 | IBOD = 96.67 − 7 (BOD) |
| 10 - 30 | IBOD = 38.9 − 1.23 (BOD) | |
| >30 | IBOD = 2 | |
| pH | 2 - 5 | IpH = 16.1 + 7.35 × (pH) |
| 5 - 7.3 | IpH = −142.67 + 33.5 × (pH) | |
| 7.3 - 10 | IpH = 316.96 − 29.85 × (pH) | |
| 10 - 12 | IpH = 96.17 − 8.0 × (pH) | |
| <2, >12 | IpH = 0 | |
| FC (counts/100ml) | 1 - 103 | IFC = 97.2 − 26.6 × log(FC) |
| 103 - 105 | IFC = 42.33 − 7.75 × log(FC) | |
| >105 | IFC = 2 |