ORIGINAL PAPER Groundwater chemical and fecal contamination assessment of the Jerba unconfined aquifer, southeast of Tunisia Faiza Souid 1 & Belgacem Agoubi 1 & Mohamed Hamdi 1 & Faten Telahigue 1 & Adel Kharroubi 1 Received: 1 October 2015 /Accepted: 3 April 2017 # Saudi Society for Geosciences 2017 Abstract Located in the southeast of Tunisia, on the Mediterranean Sea, Jerba Island has a semiarid climate condi- tion. The surface water scarcity has made groundwater the main source to supply the domestic, touristic, and agricultural water demand. Unconfined aquifer is a vulnerable costal aquifer sys- tem that undergoes several phenomena. This work aims at assessing the geochemical and bacteriological groundwater quality, defining groundwater pollution sources and promoting sustainable development and effective management of ground- water resources in Jerba Island. Data were collected after the wet season in 2014 from 79 wells. Electric conductivity, pH, TDS, and major and fecal tracers (total coliforms, thermotolerant coliforms, Escherichia coli, and Salmonella) were analyzed. Geochemical modeling including the relation- ships between geochemical tracers Na + vs. Cl - , Ca 2+ vs. Cl - , K + vs. Cl - , representative ionic ratios (Br - /Cl - , Na + /Cl - , Mg 2+ / Ca 2+ ), and statistical analysis were used to specify major pro- cess contributing to groundwater pollution and main factors controlling groundwater mineralization in the island. Groundwater varieties were hydrochemically classified into three types in terms of salinity values: group 1 (8.86%) to fresh water, group 2 (27.84%) to brackish water, and group 3 (63.29%) belongs to saline water. In addition, groundwater quality revealed high concentrations in chemical pollution tracers (Na + , Cl - , SO 4 2- , and NO 3 - ) and fecal tracers. Besides, most of the sampled wells were contaminated with nitrate (50.63%). Also, thermotolerant coliforms and E. coli were detected in all groundwater samples (96.2% of wells). Results indicated that the Jerba shallow aquifer was under seri- ous threat from both natural and anthropogenic contamination. However, the wild discharge of domestic effluents, septic tanks, and sewage were the main origins of underground water con- tamination in Jerba Island. The reduction of fecal sources, through constructing normalized latrines is thus recommended. Keywords Unconfined aquifer . Chemical pollution . Bacteriological contamination . Seawater intrusion . Jerba Island . Tunisia Introduction Groundwater can be polluted with viruses, bacteria, and other pollutants coming from several origins (Coleman et al. 2013). Identifying contamination refers to a combination of several approaches like geochemical, isotopic, bacteriological, and statistical methods (Marjoua et al. 1997; Fakir et al. 2001; El Moujabber et al. 2006; Ben Hamouda et al. 2009; Kouzana et al. 2009; Mondal et al. 2010; Malana and Khosa 2011; Belghiti et al. 2013; Yu et al. 2013; Kim et al. 2014; Kumar 2014). Groundwater quality deterioration and aquifer vulner- ability due to anthropogenic activities can be studied using the DRASTIC model coupled to Geophysical Information System (Smida et al. 2010; Ben Brahim et al. 2012). * Faiza Souid faizasouid@yahoo.fr Belgacem Agoubi belgacem.agoubi@isstegb.rnu.tn Mohamed Hamdi hamdi.inat@gmail.com Faten Telahigue faten_telahigue@yahoo.fr Adel Kharroubi adel.kharroubi@voila.fr 1 RU: Applied Hydrosciences Research Unit, Higher Institute of Water Sciences and Techniques, University of Gabès, Campus Universitaire, 6072 Gabès, Tunisia Arab J Geosci (2017) 10:231 DOI 10.1007/s12517-017-2981-5