## 4 Conclusions  
Today, in many regions worldwide, groundwater is the main source for domestic, agricultural and industrial water supply. However, the risk of pollution phenomena has become a serious problem for the quality of groundwater reserves. This problem is widely known in countries with semi-arid and arid climates due to low rainfall and high over-exploitation of aquifers following the increase in demand for drinking-water supply and water for the agricultural and industrial sectors. This high demand for water causes a rapid drawdown in aquifers. In this work, the concept of groundwater vulnerability was used in the Tebessa-Morsott alluvial aquifer (northeastern Algeria). A new proposed approach for assessing groundwater vulnerability was considered that integrates a numerical model (MODFLOW model) and an index-overlay method (DRASTIC method) to predict actual and future groundwater vulnerability and the groundwater resource sustainability of the Tebessa-Morsott alluvial aquifer. The model was calibrated and used to predict the piezometric level fluctuations for the period from 2010 to 2030 under two scenarios of water demand, where the exploitation rate was the important parameter in the simulation. The results of this calibration show that the simulated piezometric level fluctuations continue to decline over a period of 20 years, with the drawdown varying between 12 and 40 meters. The obtained results of the DRASTIC method application based on the data for the reference year (2010) indicates that the risk of pollution is significant since the aquifer is characterized mainly by average and high vulnerability (about 97%). Furthermore, nitrate concentration data confirmed this critical situation. The results of the new proposed approach, which considers the integration of the MODFLOW model and the DRASTIC method to predict actual and future groundwater vulnerability for the year 2030 in the Tebessa-Morsott alluvial aquifer, indicate:  
1. The study area is classified at a average-high pollution risk of groundwater and environmental deterioration. 2. The increase or decrease in the pollution risk for groundwater (high or low vulnerability) is closely related to the piezometric level variation (groundwater depth) caused by the pumping rate (overexploitation or pumping reduction). 3. Overexpression ensures the protection of the water table (deep piezometric level) from all pollution types observed on the ground surface. 4. Conversely, overexploitation has a negative effect on the hydrodynamic state of the aquifer: significant drawdown, depletion of the water table, etc. 5. Some measurements should be proposed to protect this groundwater system. For better groundwater management of the experimental site, artificial recharge by treated wastewater from the study area supplemented by a hydrochemical control is recommended. This technique has been successfully tested in arid and semi-arid regions by several authors [55; 56; 57; 58]. Finally, the results of this new proposed approach are satisfactory and can be applied to predict actual and future groundwater vulnerability in many regions with semi-arid and arid climates. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app12189205/s1](https://www.mdpi.com/article/10.3390/app12189205/s1)]([https://www.mdpi.com/article/10.3390/app12189205/s1](https://www.mdpi.com/article/10.3390/app12189205/s1)). Figure S1: Geological map of the study area; Figure S2: piezometric map in the Tebessa-Morsott plain (May 2010); Figure S3: Hydrogeologicalcross-section in the Tebessa-Morsott plain; Figure S4: Comparison of the DRASTIC model with the nitrate values; Table S1: Original DRASTIC weights and rating systems. Conceptualization, A.B. and M.B. ; methodology, M.B., T.D. and A.R. ; investigation, A.B., T.D. and M.B. ; writing--original draft preparation, A.B., D.M. and M.B. ; writing--review and editing, G.B. and D.M. ; supervision, A.B. and D.M. All authors have read and agreed to the published version of the manuscript.