geosciences Article Assessment of Groundwater Vulnerability to Nitrate Based on the Optimised DRASTIC Models in the GIS Environment (Case of Sidi Rached Basin, Algeria) Sbargoud Saida 1,*, Hartani Tarik 2, Aidaoui Abdellah 2, Herda Farid 1 and Bachir Hakim 1 1 Division of Hydraulic and Bioclimatology, National Institute of Agronomic Research (INRA), 2 Rue des Frères Ouaddek, BP.200 Hacen Badi El Harrach, Algeria;
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[email protected]; Tel.: +213-771-955-572 Academic Editors: Peiyue Li, John A. Luczaj, Michael Schneider and Jesus Martinez-Frias Received: 2 November 2016; Accepted: 21 March 2017; Published: 31 March 2017 Abstract: The DRASTIC model was tested on the Mitidja aquifer to assess vulnerability to nitrate pollution. Vulnerability indexes were obtained from classic DRASTIC (MDC) and pesticide DRASTIC (MDP) coupled with a geographic information system in which the weights of the model’s parameters were calculated using two weighting techniques: analytic hierarchy process (AHP) and single parameter sensitivity analysis (SPSA). The correlations between vulnerability indexes produced by both models and actual nitrate concentration values—measured from 34 system aquifers—show that the best combination is obtained from MDP–AHP (R = 0.72) followed by MDP–SPSA (R = 0.68), MDC–AHP (R = 0.67), MDC–SPSA (R =0.65), MDP (R = 0.64) and lastly MDC (R = 0.60).