Assessment of the physicochemical water quality of the Moulouya River, Morocco, using the SEQ-Eau index

Surface water is subject to strong anthropogenic pressures caused by the development and extension of agricultural activities and also by industrial and domestic activities. As a result, rational and sustainable management of water resources is necessary in order to protect them. The objective of this work is the use of geographic information system GIS and the application of the weighted index of the water quality evaluation system SEQ-Eau for the overall assessment of the physicochemical quality of surface waters of the Moulouya River. First, a cartographic representation of the study area was produced with the development of quality maps for the various alterations relating to acidification, temperature, mineralization, phosphorus materials, and organic and oxidizable materials. The overall quality map is generated from the lowest index of all the alterations considered. The results generally show surface water of excellent quality in the Upper Moulouya and of average to poor quality in the Middle and Lower Moulouya. The alteration of water, linked mainly to mineralization and phosphorus nutrients, organic and oxidizable matter, reveals a domestic type pollution in relation to urban wastewater and agricultural discharges in addition to the impact of the geological substratum of the watershed. The seasonal impact is influenced by the increase in the degree of deterioration of water quality due to the increase in the concentration of pollutants and the decrease in precipitation during the summer season.