Miftah et al. (2025) Moroccan water resources under pressure: Challenges of groundwater quality and nitrate contamination

Identification

Journal: Journal of Hydrology Regional Studies
Year: 2025
Date: 2025-09-04
Authors: Meryem Miftah, Yassine Ait Brahim, Mohammed Hssaisoune, Ayoub Ayaou, Hamza Berrouch, Lhoussaine Bouchaou
DOI: 10.1016/j.ejrh.2025.102724

Research Groups

International Water Research Institute, University Mohammed VI Polytechnic, Benguerir, Morocco
Department of Earth and Environmental Sciences, University of Pavia, Pavia, Italy
Laboratory of Applied Geology and Geo-Environment, University Ibn Zohr, Agadir, Morocco
Faculty of Applied Science, University Ibn Zohr, Ait Melloul, Morocco
Geotop-UQAM, Hydro Sciences, Department of Earth and Atmospheric Sciences, University of Quebec at Montreal (UQAM), Montreal, Quebec, Canada
Département de Géomatique, Université de Sherbrooke, Sherbrooke, QC, Canada

Short Summary

This study provides a comprehensive overview of surface and groundwater quality across Morocco, identifying widespread nitrate contamination in numerous aquifers, primarily from agricultural fertilizers, domestic/industrial wastewater, and manure, often exacerbated by seawater intrusion, rendering much of the groundwater unsuitable for drinking and irrigation.

Objective

To give an overview of groundwater and surface water quality across Morocco.
To identify aquifers suffering from nitrate contamination.
To determine the origin of this contamination.
To assess the suitability of this groundwater for both drinking and irrigation purposes.

Study Configuration

Spatial Scale: Country of Morocco, focusing on 29 aquifers divided into four groups (Atlantic, Mediterranean, Atlas, North-eastern), and major rivers and dams.
Temporal Scale: Surface water data from 2018–2020. Groundwater nitrate concentration data (1099 data points) compiled from various campaigns spanning from 1994 to 2023.

Methodology and Data

Models used: Nitrate Pollution Index (NPI), statistical parameters (boxplot, correlation matrix with p-value < 0.01), Kendall diagram, World Health Organization (WHO) guidelines, United States Salinity Laboratory (USSL) charts, Wilcox charts, Sodium Adsorption Ratio (SAR), and Sodium percentage (%Na) calculations.
Data sources: Data from the General Directorate of Waters and the Hydraulic Basin Agencies of Morocco (25 dam data points, 172 river data points, 1099 groundwater nitrate data points), hydrochemical parameters (e.g., electrical conductivity, chloride, calcium, magnesium, potassium, sulfate), and stable isotopes of nitrates (δ¹⁵N–NO₃ and δ¹⁸O–NO₃) collected from literature for BouAreg and Massa aquifers.

Main Results

Moroccan rivers generally exhibit good to moderate water quality, except for 37 % of stations downstream of domestic and industrial discharge points. Dams maintain excellent to moderate quality, with only 5 % showing poor quality due to wastewater discharge.
Groundwater quality is deteriorating across Morocco, primarily due to elevated nitrate levels and high salinity. Nitrate contamination is widespread, with highest concentrations exceeding 100 mg/l in many aquifers, indicating very poor quality.
Aquifers such as Chaouia, R’mel, Mnasra, Gharb, and Triffa are among the most heavily contaminated, with over 70 % of samples showing bad to very bad nitrate quality.
The main sources of nitrate contamination are excessive use of agricultural fertilizers, domestic and industrial wastewater discharge, manure, septic tanks, and animal waste.
Significant positive correlations between nitrate and chloride, calcium, and magnesium in several Atlantic aquifers (e.g., Berrechid, Chaouia, Mnasra) suggest common origins from animal waste, septic tank leakage, and wastewater.
Seawater intrusion exacerbates nitrate contamination in Atlantic aquifers (e.g., Chaouia, Doukkala, Akermoud), with extreme nitrate levels observed within 2000 meters of the coast, potentially by limiting denitrification.
Isotopic analyses (δ¹⁵N–NO₃ and δ¹⁸O–NO₃) in BouAreg and Massa aquifers confirm manure, sewage, and agricultural fertilizers as predominant nitrate sources. Denitrification was observed in some wells of the Massa aquifer and one well in the BouAreg aquifer.
Most groundwater in Morocco is unsuitable for drinking due to high nitrate concentrations (exceeding 50 mg/l) and/or elevated salinity (electrical conductivity > 2700 µS/cm, chloride > 750 mg/l).
For irrigation, groundwater from Moulouya, Beni-Znassen, and Mnasra is suitable (moderate salinity, low sodium). However, many aquifers (e.g., Berrechid, Chaouia, Coastal-Souss, Foum El Oued, BouAreg, Triffa, Zagora) contain groundwater unsuitable for irrigation due to extreme sodicity and high salinity.

Contributions

Provides a comprehensive, country-wide synthesis of surface and groundwater quality in Morocco, identifying and quantifying nitrate contamination across numerous aquifers.
Systematically determines the diverse origins of nitrate pollution using multiple hydrochemical and isotopic approaches, including the role of seawater intrusion in exacerbating contamination.
Assesses the suitability of groundwater for both drinking and irrigation purposes across a wide range of Moroccan aquifers, offering practical implications for water resource management.
Serves as a crucial reference for decision-makers to develop efficient and targeted water management strategies to safeguard groundwater resources.

Funding

IsoTrace project (funded by OCP Foundation)
AgreeMed project (funded by MESRSI within the framework of PRIMA program (EU))
GEANTech (funded by MESRSI and the OCP Foundation within the framework of APRD research program)

Citation

@article{Miftah2025Moroccan,
  author = {Miftah, Meryem and Brahim, Yassine Ait and Hssaisoune, Mohammed and Ayaou, Ayoub and Berrouch, Hamza and Bouchaou, Lhoussaine},
  title = {Moroccan water resources under pressure: Challenges of groundwater quality and nitrate contamination},
  journal = {Journal of Hydrology Regional Studies},
  year = {2025},
  doi = {10.1016/j.ejrh.2025.102724},
  url = {https://doi.org/10.1016/j.ejrh.2025.102724}
}

Original Source: https://doi.org/10.1016/j.ejrh.2025.102724