Evaluation of water quality of Oum Er Rbia River (Morocco) using water quality index method

The objective of the present study is to investigate the spatiotemporal variation analysis of water quality and identification of water pollution sources in Oum Er Rbia river. To evaluate the water quality of river, physico‐chemical analysis of water samples taken from eight stations in dry and in wet seasons along the Oum Er Rbia river were studied. These stations were monitored for 20 parameters; water temperature, potential Hydrogen, dissolved oxygen, electrical conductivity, total Hardness, turbidity, complete alkalimetric title, organic matter (oxidizability), chlorides, sulphates, nitrates, nitrites, ammonium, iron, copper, lead, cadmium, nickel, chromium and zinc. Results of water samples were compared with Moroccan Standards for drinking water and permitted values recommended by World Health Organization. Results indicated that the water quality parameters are over Moroccan Standards for drinking water in some stations. Seasonal variation was observed in the physicochemical composition of water in the wet compared to the dry period. Water quality index (WQI), which is an important and unique rating to represent the overall water quality in a single term that is useful to determine the suitability of water for human consumption, was also estimated. The water quality index method was used to evaluate water quality classification for drinking purpose; it is calculated for each sampling station studied using 19 parameters. Based on 19 parameters; the range obtained without including the heavy metals for calculation of WQI was from 75.92(S1) to 243.12 (S6) and from 79.05 (S1) to 464.34 (S6) indicating a good to very poor quality and a good to unsuitable for drinking in dry and wet period respectively. When the calculation of the WQI to assess the water quality along the river was included the heavy metals, it observed that all the WQI values exceeded the limit of 300 in all stations indicating the water unsuitable for drinking in the river. This study indicates that the water of Oum Er Rbia River is potentially dangerous to health of the users and signaled the necessity to treat industrial and municipal wastewater and to encourage sustainable agricultural practices to avoid adverse health effects.