Evaluation of Groundwater Quality and Contamination Using the Groundwater Pollution Index (GPI), Nitrate Pollution Index (NPI), and GIS

Groundwater is an essential and indispensable resource, meeting dire needs for drinking and irrigation purposes. The aim of this study is to assess the suitability of groundwater quality for drinking purposes. This evaluation will be conducted using the Groundwater Pollution Index (GPI), the nitrate pollution index (NPI), and the geographic information system (GIS) in Sidi Slimane, Morocco. In this study, a comprehensive collection of 20 samples was obtained from various locations for analysis and evaluation. Hadrochemical facies of this study area showed that out of 20 samples, 90% belonged to a type (Na⁺-K⁺-Cl⁻-SO₄²⁻), while only 10% fell into a category (Ca²⁺-Mg²⁺-Cl⁻-SO₄²⁻). The Groundwater Pollution Index values ranged from 0.7 to 10.8, with an average of 7.03; about 60% of the groundwater samples analyzed in this study area were classified as highly polluted and unsuitable for drinking purposes. Nitrate index values ranged from −0.9 to 10.5. Approximately 80% of the sampled sites require treatment before consumption. According to the Nitrate Pollution Index (NPI), it is essential to regularly monitor 16 well sites to prevent nitrate contamination resulting from human activities, including waste disposal in open areas and sewage infiltration. This study recommends raising farmers’ awareness of the use of slow-release natural fertilizers made from nitrogen rather than nitrogen-based fertilizers, reducing waste disposal by residents, and maintaining an appropriate sewage network to minimize sewage flow leakage. This study plays a vital role in identifying the polluted areas and highlighting the need to take appropriate measures to control the sources of pollution in this study area in order to protect water resources and ensure the provision of safe water to the local population.