Assessment of spatial and seasonal water quality variation of Oum Er Rbia River (Morocco) using multivariate statistical techniques

TLDR

The study aims to evaluate spatial and temporal water quality variations and identify main contamination sources in the Oum Er Rbia River and its tributary, El Abid River. Water quality data from 14 stations (2000–2012) were analyzed using Pearson correlation, PCA, and CA on indicators such as temperature, pH, EC, turbidity, TSS, DO, ammonium, ammonia, total phosphorus, BOD5, COD, and fecal coliform. Results show that several stations exceed Moroccan standards, with PCA revealing four factors (~63 % of variation) linked to point‑source, non‑point‑source, and natural contamination, while CA indicates spatial and seasonal changes; overall the water poses health risks, underscoring the need for wastewater treatment, sustainable agriculture, and prudent catchment management.

Abstract

The aim of this study is to assess the spatial and temporal water quality variation and to determine the main contamination sources in the Oum Er Rbia River and its main tributary, El Abid River. The water quality data were collected during 2000–2012 from fourteen sampling stations distributed along the river. The water quality indicators used were TEMP, pH, EC, turbidity, TSS, DO, NH4+, NH3–, TP, BOD5, COD and F. coli. The water quality data was analyzed using multivariate statistical methods including Pearson's correlation, PCA, and CA. The results showed that in some stations the water quality parameters were over Moroccan water standards. PCA applied to compare the compositional patterns among the analyzed water samples, identified and four factors accounting for almost 63% of the total variation in the data. This suggests that the variations in water compounds’ concentration are mainly related to point source contamination (domestic and industrial wastewater), non-point source contamination (agriculture activities), as well as natural processes (weathering of soil and rock). CA showed relatively spatial and seasonal changes in surface water quality, which are usually indicators of contamination with rainfalls or other sources. Overall, this study showed that the water was potentially hazardous to health of the consumers and highlighted the need to treat industrial and municipal wastewater and to encourage sustainable agricultural practices to prevent adverse health effects. We therefore suggest wise management of anthropogenic activities in the catchment of Oum Er Bia River and their tributaries.