From Index to Decision: A Critical Review of Water Quality Indices Applied to Moroccan Waters (2018–2025)

Abstract

Water Quality Indices (WQIs) are widely used to synthesize information on water quality and support decision-making. In Morocco, their application has grown significantly in recent years for the assessment of surface and groundwater. However, the diversity of indices, parameters used, weighting schemes, and reporting practices limits the comparability and robustness of results. This study offers a critical analysis of the applications of WQIs to Moroccan waters over the period 2018–2025, based on a systematic review of 244 articles indexed in Scopus. The results highlight significant methodological heterogeneity, notable classification differences for comparable contexts, and a lack of transparency regarding the management of missing data and uncertainties. In order to strengthen the scientific and decision-making value of WQIs, a minimal harmonization framework adapted to the semi-arid Moroccan context is proposed, based on a common set of parameters, explicit data processing rules, double reading by reference indices, and standardized reporting.