TITLE:
Groundwater Vulnerability Assessment to Nitrogen Pollution Using a GIS-Based DRASTIC Model in the Area of the 9th District of N’Djamena, CHAD
AUTHORS:
Tidjani Bahar, Ousmane Mahamat, Djimadjimbaye Eraste
KEYWORDS:
DRASTIC, GIS, Groundwater Vulnerability, Nitrate Concentration, 9th District of N’Djamena
JOURNAL NAME:
Journal of Environmental Protection,
Vol.17 No.6,
June
12,
2026
ABSTRACT: Groundwater resources are the primary source of water for human activities. Therefore, controlling groundwater contamination through the assessment of its vulnerability is crucial for effective water management and protection. In this work, the GIS-based DRASTIC model has been used to assess the groundwater vulnerability of the area of the 9th district of N’Djamena, CHAD. A total of 7 hydrogeological factors, such as depth to water level, net recharge, aquifer media, soil media, topography, impact of the vadose zone, and hydraulic conductivity, have been used for this study. The final groundwater vulnerability map was obtained by overlaying a weighted method with the help of the DRASTIC index. The results of the study showed that the DRASTIC vulnerability index (DI) value varies from 115 to 165, and the catchment area studied can be classified into three vulnerability classes (low, average, and high). The high vulnerability class covers 15% of the study area. The average and low vulnerability classes cover approximately 34% and 51% of the study site, respectively. In the northeastern portion of the 9th district of N’Djamena, namely Toukra, Walia, and Kabe, high vulnerability to contamination has been observed. To validate the groundwater vulnerability map, the water quality parameter—nitrate—has been used. The Pearson correlation coefficient between groundwater vulnerability (DRASTIC index) and nitrate concentrations showed a strong positive correlation (r = 0.76) when validating the groundwater vulnerability map. The groundwater vulnerability map obtained in this study can be widely used for better management of groundwater and land use planning.