Moroccan water resources under pressure: Challenges of groundwater quality and nitrate contamination

Country of Morocco, north-western part of Africa. In numerous regions worldwide, groundwater serves as the primary source of drinking water supply. However, the increase of industrial and agricultural activities, as well as the succession of drought periods in regions such as Morocco have led to water scarcity and the introduction of pollutants into ground and surface water. Nitrate (NO₃⁻), due to its high solubility, has become a pervasive contaminant, presenting an increasingly detrimental issue over time, particularly in arid environments such as Morocco. Hence, the goal of this work is to give an overview of groundwater and surface water quality across Morocco. Specifically, the research aims to identify aquifers suffering from nitrate contamination, determine the origin of this contamination, and assess the suitability of this groundwater for both drinking and irrigation purposes. In general, Moroccan rivers exhibit good to moderate water quality, except for localized areas downstream of domestic and industrial discharge points. Dams generally maintain excellent to moderate water quality, with only 5 % showing bad quality attributed to wastewater discharge. On the other hand, groundwater witnesses a deterioration in their quality, primarily due to elevated nitrate levels and high salinity. Nitrate contamination is prevalent in many aquifers in Morocco with the highest concentrations exceeding 100 mg/l, indicating very bad quality. This degradation stems from domestic and industrial wastewater discharge and excessive fertilizer use in irrigated areas. Additionally, nitrate contamination worsened by seawater intrusion, observed in Atlantic aquifers like Chaouia, Doukkala and Akermoud, especially within 2000 m of the sea. Furthermore, isotopic analyses of δ¹ ⁵N–NO₃ and δ¹ ⁸O–NO₃ in both the Mediterranean aquifers “BouAreg” and Atlantic aquifers “Massa” indicate that the main sources of nitrate are likely manure, sewage, and agricultural fertilizers used in irrigated areas. The denitrification phenomenon was detected in some wells of the Massa aquifer characterized by an enrichment of ¹ ⁵N and low NO₃⁻ content, however this process only affects one well in the BouAreg aquifer. This comprehensive overview might serve as a reference for decision-makers to build efficient water management strategies. • More than ten Moroccan aquifers are affected by nitrate contamination. • Agricultural practices and wastewater are the main sources of this contamination. • Among 28 Moroccan aquifers, 16 are deemed unsuitable for drinking water. • Most Moroccan groundwater can be used for irrigation under specific conditions.