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Ain Sefra is one of the Algerian cities that had been experienced several devastating floods during the past 100 years. The purpose of this study is to simulate runoff in the semi-arid region of Ain Sefra watershed through the employing of the Hydrologic Engineering Center – Hydrologic Modelling System (HEC-HMS). In this paper, the frequency storm is used for the meteorological model, the Soil Conservation Service – curve number (SCS-CN) is selected to calculate the loss rate and Soil Conservation Service unit hydrograph method have been applied to simulate the runoff rate. After calibration and validation, the simulated peak discharges were very close with observed values. The Nash–Sutcliffe efficiency coefficient was 0.95, indicates that the hydrological modeling results are satisfactory and accepted for simulation of rainfall-runoff. The peak discharges obtained for the 10, 50, 100 and 1000 year storms are respectively 425.8, 750.5, 904.3 and 1328.3 m3∙s−1.

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Naâma watershed is situated in the southwest of Algeria, where the climate is arid. It is highly dependent on groundwater resources, which are the only available resources for irrigation and domestic purposes. The study was carried out to assess groundwater appropriateness in the study area for drinking uses through a water quality index (WQI) and geographic information system (GIS). Fourteen (14) groundwater samples were collected, and several physicochemical parameters such as electrical conductivity (EC), potential for hydrogen (pH), total dissolved solids (TDS), cations (Ca, Mg, Na, K), and anions (SO4, NO2, HCO3, Cl) were analyzed. The results report that the different water quality parameters were within the permissible limit given by the World Health Organization and Algerian Standards guidelines, except for some boreholes near the Sabkha of Naâma. Eleven (11) parameters were chosen to compile the water quality index. The results showed that 50% of groundwater sites sampled in the study area had excellent water quality, while 50% were suitable. By carefully examining the data, it was revealed that boreholes distant from Sabkha present an excellent groundwater quality, where the WQI ranges between 37 and 41.6 mg/L. On the other hand, the boreholes close to Sabkha are characterized by a high concentration of electrical conductivity, TDS, sodium, and sulfates, explained by the contamination of the surrounding area through the infiltration of salt elements from the Sabkha. This salt contamination of groundwater would be accentuated by the discharge of wastewater from Naâma town into the Sabkha, the irrational use of chemical fertilizers, pesticides, and intensive pumping. The spatial distribution of the physicochemical parameters and water quality index was generated using the inverse distance weighted interpolation method (IDW). This study demonstrates that the combination of WQI and GIS methods could be a helpful tool for water resources management and decision making.

Remote sensing (RS) and Geographic Information Systems (GIS) have become widely used in various fields around the world in recent years. In this paper; we attempt to delineate the groundwater potential zone in the transboundary watershed of Chott-El-Gharbi using the integration of RS, GIS methods. Eight influencing thematic layers viz. geology, rainfall, water table level, lineaments density, slope, drainage density, elevation, and land use/land cover were used. Afterward, Analytical Hierarchy Process technique, which offers good functionality for mapping the groundwater potentiality was used, where ranks and weights, assigned to each factor are computed statistically, based on their relative importance in terms of groundwater potential. Then, groundwater potential zones are classified into five categories namely excellent, high, medium, low, and very low zone, which represent 964.48 km2 (7.33%), 1467.30 km2 (11.15%), 7969.51 km2 (60.57%), 2639.52 km2 (20.06%), and 116.19 km2 (0.88%) of the study area, respectively. The very low potential region is found in the southern region of the study area, which is covered by mountains. Moreover, excellent groundwater potential zones are located at the central part of the region of Chott, which has quaternary formations where the infiltration is high. On the other hand, moderate and poor groundwater potential zones cover by the bare lands in the study area. Finally, the results were carefully validated with the yields data of various boreholes in the study area, which reveals an accuracy achievement of 72.41%. The finding of this research constitutes a valuable contribution towards the water resources management, and it forms a significant decision support tool for equitable and sustainable utilization of groundwater resources in the transboundary watershed of Chott-El-Gharbi. The study's findings will also serve as a benchmark for future research and studies, such as hydrogeological modeling.