Evolution of the Physico-Chemical and Biological Quality of the Waters of Soueir River (Morocco)

Abstract

As part of the monitoring of water quality of Soueir river, two sampling companions were conducted from April to February during the two periods 2016/2017 and 2018/2019. The study consists of measuring 14 physico-chemical parameters and establishing the inventory of benthic macroinvertebrates upstream and downstream of Soueir river. The physico-chemical parameters were used to calculate the water quality index (WQI) and the exploitation of the results of the fauna inventory allowed us to determine the Shannon - Weiner diversity index (H') and the Belgian biological index (BBI). The comparative study of the results of the two periods shows that: - During the two sampling periods, the recorded values of the physico-chemical parameters are lower than the admitted standards, except for nitrates and ammonium which present high levels during certain periods of the year, sometimes exceeding the Moroccan standards. These high concentrations can be explained by the excessive use of chemical fertilizers in the activity and the decrease of the water flow. - The calculation of the water quality index (WQI) reveals that the water quality varies with a tendency towards degradation from upstream to downstream, the water becomes of poor quality or even non-drinkable. - The values of the BBI indicate that the water of Soueir river is not very polluted, and that the quality of the water decreases during the winter period due to the erosion of the substrate and the increase of the matter in suspension. - The diversity of benthic macroinvertebrates is greater downstream, due to the diversity of habitats and substrates. - The second sampling period reveals a slight improvement in the physico-chemical and biological qualities of the waters of Soueir river, which can be attributed to climatic conditions that were more favorable to the development cycles of benthic macro-invertebrates

Keywords

• soueir river
• physico-chemical parameters
• benthic macroinvertebrates
• water quality index
• biotic index