The DUPIT index is one of the weighting/rating driven indicators that are related to the index and overlay approach (Simsek et al. 2005). It is determined to infer the protectability of the groundwater against diffuse pollution through the unsaturated zone and to delineate the zones of high or low vulnerability to this hazard. The hydrogeochemical, hydrogeological and physical factors inherent in the system (Depth to groundwater table, Upper layer lithology, Permeability of the unsaturated zone, Impermeable layer thickness and Topographic slope) are explored and assigned weighting and rating scores, Table 13 (Simsek et al. 2005), based on their values in the different water points. An overall DUPIT index is calculated from these scores as follows:
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Table 13
DUPIT index parameters and their classification (Simsek et al. 2005)
| Factor | Weight | Range | Rating | Suitability |
|---|---|---|---|---|
| Depth to groundwater table | 5 | <5 | 1 | Very Low |
| 5–15 | 2 | Low | ||
| 15–30 | 3 | Medium | ||
| 30–50 | 4 | High | ||
| >50 | 5 | Very High | ||
| Upper layer lithology | 4 | Fractured rocks | 1 | Very Low |
| Sand and gravel | 2 | Low | ||
| Silty sand, clayey and silty gravel | 3 | Medium | ||
| Silty and clayey sand | 4 | High | ||
| Clay, schists and flysch, massive rocks | 5 | Very High | ||
| Permeability of unsaturated zone (m/s) | 3 | >1.0 × 10−2 | 1 | Very Low |
| 1.0 × 10−2– 1.0 × 10−3 | 2 | Low | ||
| 1.0 × 10−3– 1.0 × 10−5 | 3 | Medium | ||
| 1.0 × 10−5– 1.0 × 10−7 | 4 | High | ||
| <1.0 × 10−7 | 5 | Very High | ||
| Impermeable thickness (m) | 2 | <3 | 1 | Very Low |
| 3–6 | 2 | Low | ||
| 6–12 | 3 | Medium | ||
| 12–24 | 4 | High | ||
| >24 | 5 | Very High | ||
| Topographic slope (o) | 1 | >60 | 1 | Very Low |
| 40–60 | 2 | Low | ||
| 20–40 | 3 | Medium | ||
| 10–20 | 4 | High | ||
| <10 | 5 | Very High |
| Factor | Weight | Range | Rating | Suitability |
|---|---|---|---|---|
| Depth to groundwater table | 5 | <5 | 1 | Very Low |
| 5–15 | 2 | Low | ||
| 15–30 | 3 | Medium | ||
| 30–50 | 4 | High | ||
| >50 | 5 | Very High | ||
| Upper layer lithology | 4 | Fractured rocks | 1 | Very Low |
| Sand and gravel | 2 | Low | ||
| Silty sand, clayey and silty gravel | 3 | Medium | ||
| Silty and clayey sand | 4 | High | ||
| Clay, schists and flysch, massive rocks | 5 | Very High | ||
| Permeability of unsaturated zone (m/s) | 3 | >1.0 × 10−2 | 1 | Very Low |
| 1.0 × 10−2– 1.0 × 10−3 | 2 | Low | ||
| 1.0 × 10−3– 1.0 × 10−5 | 3 | Medium | ||
| 1.0 × 10−5– 1.0 × 10−7 | 4 | High | ||
| <1.0 × 10−7 | 5 | Very High | ||
| Impermeable thickness (m) | 2 | <3 | 1 | Very Low |
| 3–6 | 2 | Low | ||
| 6–12 | 3 | Medium | ||
| 12–24 | 4 | High | ||
| >24 | 5 | Very High | ||
| Topographic slope (o) | 1 | >60 | 1 | Very Low |
| 40–60 | 2 | Low | ||
| 20–40 | 3 | Medium | ||
| 10–20 | 4 | High | ||
| <10 | 5 | Very High |