No abstract

The drinking and irrigation water scarcity is a major global issue, particularly in arid and semi-arid zones. In rural areas, groundwater could be used as an alternative and additional water supply source in order to reduce human suffering in terms of water scarcity. In this context, the purpose of the present study is to facilitate groundwater potentiality mapping via spatial-modelling techniques, individual and ensemble machine-learning models. Random forest (RF), logistic regression (LR), decision tree (DT) and artificial neural networks (ANNs) are the main algorithms used in this study. The preparation of groundwater potentiality maps was assembled into 11 ensembles of models. Overall, about 374 groundwater springs was identified and inventoried in the mountain area. The spring inventory data was randomly divided into training (75%) and testing (25%) datasets. Twenty-four groundwater influencing factors (GIFs) were selected based on a multicollinearity test and the information gain calculation. The results of the groundwater potentiality mapping were validated using statistical measures and the receiver operating characteristic curve (ROC) method. Finally, a ranking of the 15 models was achieved with the prioritization rank method using the compound factor (CF) method. The ensembles of models are the most stable and suitable for groundwater potentiality mapping in mountainous aquifers compared to individual models based on success and prediction rate. The most efficient model using the area under the curve validation method is the RF-LR-DT-ANN ensemble of models. Moreover, the results of the prioritization rank indicate that the best models are the RF-DT and RF-LR-DT ensembles of models.

Présenté par Ghislain de Marsily RésuméDes analyses chimiques et isotopiques des eaux ont été utilisées, conjointement à des analyses pétrographiques et chimiques des roches, pour déterminer l'origine des ions chlorure dans les eaux souterraines de la nappe de Chtouka-Massa (Maroc). Il apparaît que la formation schisteuse qui constitue le substratum de la nappe étudiée est à l'origine des fortes teneurs en Cl − mesurées dans certaines eaux souterraines. Dans ces schistes, une partie du chlorure est probablement contenue dans les biotites, et passe en solution lors de l'altération de ces minéraux. Toutefois, l'exceptionnelle richesse en chlorure de ces schistes est difficile à expliquer sans admettre qu'ils contiennent aussi des minéraux chlorurés de type évaporitique.