Water Quality Assessment Using a New Proposed Water Quality Index: A Case Study from Morocco

Abstract

Excellent or very poor water quality depends of its physicochemical and biological parameters. However, the assessment of water quality relies on the water quality index (WQI) used, because some indices in their form of application may underestimate or overestimate the overall water quality. For instance, to avoid the problem of underestimation of water quality index, a new WQI is proposed in this study. In order to develop this new WQI, data from 29 water quality monitoring stations, including 3 surface water stations and 26 groundwater stations, spanning over1988 -2017 , were collected from the Sebou Hydraulic Basin Agency (ABHS).The water quality parameters were standardized and then aggregated into a composite water quality index, using Moroccan water quality standards. The application of this new WQI showed that 37.9% of the stations have bad or very bad water quality, 13.8% have medium quality, 41.4% have good quality and that only 6.9% have excellent quality. The poor surface water quality, characterized by high levels of BOD5 and COD, low dissolved oxygen and high levels of fecal coliforms is mainly due to industrial and domestic activities. The poor groundwater quality marked by nitrate leaching from agricultural lands is chiefly due to industrial and domestic activities. The comparison between this new WQI and the method used by ABHS showed a satisfactory agreement of the results (R2 =0.70, at the 95% confidence level) for the 26 groundwater stations.