Salinization origin of Souf Terminal Complex: Application of statistical modelling and WQI for groundwater management

Abstract. The natural salinization of Souf sandy Terminal Complex groundwater notably Pontian and Mio-Pliocene has increased four times for the last 30 years, because of over pumping for drinking and irrigation. Application of the multivariate statistical modelling and the Water Quality Index (WOI) to evaluate the groundwater variables have been done, by the investigation of water samples collected from 25 boreholes, in May 2018. Cluster analysis identified three main water types based on the major ionic contents. Factor Analysis and Principal Component Analysis methods confirmed the cluster analysis results. The water groups have sodi-potassic facies which dominate in the western part of Souf, compared to the eastern part and they have generally poor quality. An osmosis phenomenon allowed the homogenization of Pontian and Mio-Pliocene groundwater. The contact of Terminal Complex with the Eocene dolomite and Senonian evaporitic allows introducing a new preferential dissolution corridors concept in which an underground leaching front occurs with the increased pumping. Overlying sandy rocks subsidence can be produced gradually with a rise in the static groundwater level because of the leached underground Senonian evaporitic rocks. Closure of wells intersecting the evaporitic layers and minimizing of pumping from Terminal Complex groundwater in the Southwest part of Souf is strongly recommended, and the groundwater is requiring treatment before supply.