Pandemic impacts on the water quality: statistical analysis and spatiotemporal monitoring via GIS maps

On March 11, 2020, the World Health Organization (WHO) declared the coronavirus disease 2019 infection as a global pandemic, leading hence to a series of measures to restrict human mobility, including the industries lockdown, which significantly influenced the quality of Wadi Fez water resources. This study presents the COVID-19 lockdown impact on the spatio-temporal evolution of surface water quality according to 5-year monitoring (2015–2021) using the global quality assessment system SEQ-Eau including the collection of water samples, some lab analysis, and the visualization of results through GIS tools. The same results were compiled statistically using the ANOVA approach in order to compare the spatio-temporal alterations. The evaluation of the quality of surface waters of four sites selected on the course of the Wadi Fez, and crossing mainly the district of Dokkarat, revealed that the organic and bacteriological pollution, before containment, exceeds the quality standards of surface waters and classifies these waters as being of poor quality. In addition, the concentration of fecal coliforms is very high, with a maximum value exceeding 100,000 CFU 100 mL⁻¹, especially downstream from Wadi Fez. Moreover, the sites close to the Dokkarat district are characterized by very high pollution. The results obtained by the bivariate ANOVA test and their statistical validation show that the time factor influences most of the studied alterations. However, after 2020, the quality of the physicochemistry and bacteriology watercourse has considerably improved. Over 5 years (2015–2020), the data comparison shows an average increase in physicochemical quality of 31% and increasing bacteriological quality of 16%. This period is before and after the COVID-19 confinement. The reopening of industrial units as well as the acceleration of anthropic activities can explain the substantial impact they generate. Indeed, this study highlights the impact of the human activity on the quality of superficial water flowing along Oued Fez. It suggests a direct link between periods of industrial sustainability with high rates of pollution and in contrast, and it relates the improvement of water quality to the deceleration of those activities. Otherwise, decision-makers can rely on its results to locate the sources and the nature of pollution and anticipate these environmental patterns in the case of a future similar pandemic.