2.2. Sample collection and analysisFor the purpose of this study, 20 sampling sites (Table 1) monitored monthly from 2002 to 2013 were selected. Aftercollection; salinity, temperature, dissolved oxygen and turbidity were measured promptly with portable sensors (WTWMulti 350i multimeter). The remaining variables were analyzed later at the Central Laboratory for EnvironmentalQuality Monitoring (CLEQM) of the National Water Research Center.2.3. Water quality index (WQI)According to the Canadian Council of Ministers of the Environment (CCME, 2001), Water Quality Index (CCMEWQI) provides a measure of the deviation of water quality from water quality guidelines. The CCME WQI modelconsists of three measures of variance from selected water quality objectives (scope; frequency; and amplitude). Thesethree measures of variance are combined to produce a value between 0 and 100 that represents the overall water quality(CCME, 2001).The detailed formulation of the WQI Canadian Water Quality Index consists of three measures which are describedas follows:Scope, F1: it represents the extent of water quality guideline non-compliance over the time period of interest whichwas calculated as Eq.