Use of GIS based Inverse Distance Weighted interpolation to assess surface water quality: Case of Wadi El Bey, Tunisia

Abstract

Sustainable management of water resources involves inventory, conservation, efficient utilization, and quality management. Although, activities relating to quantity assessment and management in terms of river discharge and water resources planning are given attention at the pollution level of the watershed, water quality assessment are still being done at specific locations of major concern. The use of Geographical Information System (GIS) based on water quality information system and spatial analysis with Inverse Distance Weighted (IDW) interpolation enabled the mapping of water quality indicators in watershed of Wadi El Bey, Tunisia. Using 13 sampling locations, water quality indicators were monitored from 2012 to 2016; covering full hydrological season. Maps of spatio-temporal variations in some physical parameters (Temperature, pH), chemical (chemical oxygen demand, Biochemical oxygen demand, total suspended solids...) and microbiological ones ( Fecal​ coliform, Escherichia coli, Staphylocoques ...) were used to evaluate the water quality across monitoring stations and analyze the sources of water pollution along the river courses. The production of water quality maps will improve monitoring, enforce the standards and regulations towards better pollution management and control. Patterns were clearly defined; methods were statistically valid and the IDW predictions were made to exhibit high prediction. Thus, the spatial distribution maps show that the agricultural activities, domestic, and industrial discharges are fundamental causes of water pollution in the study area specially the industrial zone of Grombalia. The results of IDW helped us to identify key areas requiring control in the Wadi el Bey River, which pointed the way for further delicacy management of the river. • The present investigation highlights the assessment of Wadi El Bey water quality. • Spatiotemporal variation of pollutants was assessed using GIS and IDW interpolation. • Models were statistically valid and the IDW was observed to exhibit high prediction. • Study area was highly contaminated by the Grombalia industrial discharges. • Water quality maps enforce regulations for better pollution management and control.