Groundwater Quality Assessment Using Indexing Approaches (WQI, MQI, and NPI) in the Meknes Region (Morocco)

In the Meknes region, groundwater is essential for drinking and irrigation. Facing growing agricultural and urban pressures, this study applies three complementary indices (Water Quality Index [WQI], Microbiological Quality Index [MQI], and Nitrate Pollution Index [NPI]) to provide an evidence-based environmental diagnosis. From December 2016 to November 2017, 14 wells were sampled. Physicochemical and bacteriological analyses followed standardized protocols. The assessment combined the WQI, MQI, and NPI with multivariate statistical analyses. Physicochemical quality complies with Moroccan standards, except at well W13. The NPI shows nitrate levels below 20 mg/L in most wells, except at W7 and W13 (moderate pollution). Systematic microbiological contamination (fecal coliforms, streptococci) was detected at all sites. The WQI ranged from 26.57 to 191.26 (high spatial variability), while the MQI (3.33–4.0) confirmed widespread fecal pollution. The contrast between good chemical quality and extensive bacterial contamination demonstrates that compliance with physicochemical standards does not guarantee water safety. Well W13, located near a landfill, illustrates the impact of point pollution sources. This study identifies priority sites (W7, W13), establishes a multi-index baseline, and proposes transferable tools for other semi-arid regions. It recommends preventive measures: well protection, improved waste management, and regular bacteriological monitoring.