The saline groundwater irrigation is an important problem in the arid and semiarid region because it can cause soil salinization and reduce crop productivity. The accurate spatial distribution of groundwater salinity can be helpful to managers and decision makers. In this study, the mapping of salinity risk through groundwater electrical conductivity (EC) irrigation was performed based on data collected from 88 wells in the Lower-Cheliff plain (Algeria). The EC data showed a normal distribution based on elementary statistics. The EC classified using Riverside method point out a high risk of groundwater salinity (Class C3) or very high risk (Class C4) for soil salinization. The EC estimated by ordinary kriging method (OK) revealed on one hand, an underprediction of a high value, on the other hand, an overprediction of low value. The methodology of nonparametric and nonlinear of indicator kriging (IK) was performed by three thresholds: EC>2.25, EC>3, and EC>5 dS/m. The map has been obtained from th...

Modelling approaches are becoming an efficient tool in the forecasting of the salinization spread impact on the local and global scales. In the Lower-Cheliff plain, updating the information on soil salinity expansion is more than required as it continues to damage the agricultural environment in there. Through this study, we adopted an artificial methodology that consists of a combination of buffer analysis using Sentinel-2 data and machine learning modelling to assess their aptitude in the prediction and mapping of soil salinity. The adopted random forest (RF) algorithm included the reflectance information from of the bands from Blue ( ${\rho }_{\mathrm{B}\mathrm{l}\mathrm{u}\mathrm{e}}$), Green ( ${\rho }_{\mathrm{G}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{n}}$), Red ( ${\rho }_{\mathrm{R}\mathrm{e}\mathrm{d}}$), Near infrared (NIR), Vegetation red-edge (VRE) and Shortwave Infrared (SWIR), optimized with the geospatial buffering based on the 91 soil random samples collected during the summer of 2019 and measured for the Electrical Conductivity (EC) in the laboratory. The outputs from the geospatial buffering refined the goodness of the correlation between field data and the variables set from bands reflectance and selected salinity indices. The obtained coefficient of determination (R ²) with Multiple Linear Regression (MLR) and Partial Least Square regression (PLS) models proved an improvement in the multivariable prediction of soil salinity with the optimized Sentinel-2 data (R ² = 0.61 and 0.68 + RMSE of 3.36 and 2.87 dS m⁻¹ respectively), compared to the results from the 2015 multiple regression model, Given the high values of R ² = 0.77 and 0.95 and the low values of RMSE = 2.29 and 1.18 dS m⁻¹ respectively; the RF regressor was very efficient in predicting EC either with all variables or with selected variables from the variable importance measure based on the mean decrease accuracy (MDA). The random forest classifier performed top of the range classification with an overall Accuracy (OA) about 99%, estimating that over 75% of the study area surface is suffering from the salinization extent.

The assessment of groundwater irrigation using robust tools is essential for the sustenance of the agro-environment in arid and semi-arid regions. This study presents a reliable method consisting of a combination of multivariate analysis and geostatistical modeling to assess groundwater irrigation resources in the Western Middle Cheliff (Algeria). For this goal, mean data from 87 wells collected during April to July 2017 were used. The hierarchical cluster analysis (HCA) using the Q-mode approach revealed three distinct water types, with mineralization increasing from cluster 1 to cluster 3. The Principal Component Analysis (PCA) utilizing the Varimax method approach allowed the extraction of three main components: the first and second (PC1, PC2), revealing that the geogenic process, have influenced the hydrogeochemical composition of groundwater. The pollution induced by agriculture activities has been related to PC3. Based on the combination of multivariate analysis and geostatistical modeling, the distribution maps were created by interpolating the factor distribution values acquired in the study region using the ordinary kriging (OK) interpolation method. The findings revealed that both natural processes and man-made activities have a substantial impact on the quality of groundwater irrigation. Cluster mapping, another often used combining approach, has shown its effectiveness in assisting groundwater resource management.

Combination of remote sensing and kriging to improve soil salinity mapping in the Hmadna plain (Algeria)