A comparison study of DRASTIC methods with various objective methods for groundwater vulnerability assessment.

Area of Science:

• Environmental Science
• Hydrogeology
• Geospatial Analysis

Background:

• Groundwater contamination risk assessment is crucial for water resource management.
• The DRASTIC model is a widely used framework for evaluating groundwater vulnerability.
• Objective methods can improve the accuracy of vulnerability assessments compared to subjective weighting.

Purpose of the Study:

• To enhance the original DRASTIC model for groundwater vulnerability assessment in the Sari-Behshahr plain, Iran.
• To compare the performance of four objective methods: Weights-of-Evidence (WOE), Shannon Entropy (SE), Logistic Model Tree (LMT), and Bootstrap Aggregating (BA).
• To evaluate the impact of incorporating eight additional factors on vulnerability mapping accuracy.

Main Methods:

• Modified the DRASTIC model using WOE, SE, LMT, and BA techniques.
• Integrated eight additional factors: distance to fault, fault density, distance to river, river density, land-use, soil order, geological time scale, and altitude.
• Validated model performance using 109 nitrate concentration data points and Area Under the Receiver Operating Characteristic (ROC) Curve (AUC).

Main Results:

• The original DRASTIC model achieved an AUC of 0.50.
• Modified DRASTIC models showed improved performance: BA (0.64), SE (0.65), LMT (0.75), and WOE (0.81).
• The WOE method with all 15 factors (7 original + 8 additional) achieved the highest AUC of 0.91, indicating superior predictive capability.

Conclusions:

• Objective methods, particularly Weights-of-Evidence, significantly improve groundwater vulnerability assessment accuracy.
• Incorporating additional relevant factors further enhances the predictive power of the DRASTIC model.
• Net recharge was identified as the most influential factor, while vadose zone impact and hydraulic conductivity were least effective.