Skip to Main Content
Each of the indicated factors has been assigned a weighting and rating scores as indicated in Table 5. Based on the values of these scores an overall GALDIT index is calculated as follows:
formula
1
where W1–W6, and GR, AR, LR, DR, IR and TR are the weighting and rating values of the six parameters, respectively. The classification of groundwater vulnerability according to the ranges of GALDIT index is indicated in Table 5.
Table 5

Rating and weighting values of different hydrogeological parameters according to their relative importance (Chachadi & Lobo-Ferreira 2001)

IndicatorWeightIndicator variables
Rating
ClassRange
Groundwater occurrence/aquifer type Confined   10 
Unconfined 7.5 
Leaky confined 
Bounded confined (Recharge and or impervious boundary aligned 2.5 
Aquifer hydraulic conductivity (m/day) High >40 10 
Medium 10–40 7.5 
Low 5–10 
V. low <5 2.5 
Height of groundwater level (amsl)(m) High <1 10 
Medium 1–1.5 7.5 
Low 1.5–5 
V. low >5 2.5 
Distance from shore/high tide (m) V. small <500 10 
Small 500–750 7.5 
Medium 750–1,000 
Fair >1,000 2.5 
Impact status of existing sea water intrusion High >2 10 
Medium 1.5–2 7.5 
Low 1–1.5 
V. low <1 2.5 
Saturated aquifer thickness (m) High >10 10 
Medium 7.5–10 7.5 
Low 5–7.5 
V. low <5 2.5 
IndicatorWeightIndicator variables
Rating
ClassRange
Groundwater occurrence/aquifer type Confined   10 
Unconfined 7.5 
Leaky confined 
Bounded confined (Recharge and or impervious boundary aligned 2.5 
Aquifer hydraulic conductivity (m/day) High >40 10 
Medium 10–40 7.5 
Low 5–10 
V. low <5 2.5 
Height of groundwater level (amsl)(m) High <1 10 
Medium 1–1.5 7.5 
Low 1.5–5 
V. low >5 2.5 
Distance from shore/high tide (m) V. small <500 10 
Small 500–750 7.5 
Medium 750–1,000 
Fair >1,000 2.5 
Impact status of existing sea water intrusion High >2 10 
Medium 1.5–2 7.5 
Low 1–1.5 
V. low <1 2.5 
Saturated aquifer thickness (m) High >10 10 
Medium 7.5–10 7.5 
Low 5–7.5 
V. low <5 2.5 
Close Modal

or Create an Account

Close Modal
Close Modal