Accessibility of fresh water, the nature's gift wheels the foremost part of the world economy. The sufficient supplies of water are essential for agriculture, human intake, industry as well as regeneration. The Oued Righ region is located in Algeria's South-East, specifically in the NorthEast of the Sahara, on the Northern edge of the Grand Erg Oriental and the Southern border of the Aures massif. This area appears as a lower Sahara synclinal basin and is part of a broad North-South trending ditch. It is famous for its date palms, the development of the date culture in this region is attributed not only to the population’s efforts, but above all to the particular climatic conditions, the favorable soil characteristics and the existence of significant groundwater. The aim of this study is to understand the results obtained from using different approaches of water hydrodynamics in the Complex Terminal aquifer. The aquifer’s hydrodynamic characterization was carried out using hydrodynamic parameters and piezometry. As a result, the transmissivity and permeability obtained data using traditional Cooper-Jacob method showed that the flow capacities of the aquifer environment and the productivities of the structures are important in the studied zone where, the highest value of transmissivity equal 2.36× 102-m 2 /sis found in the central part of the study area in El-Meghair. The establishment of piezometric maps reveals a flow direction oriented toward the chott.

The relative scarcity of water resources in Algeria and their unequal distribution induce a rational use of available resources. The Zana-Gadaïne plain appears as an exemplary case study, where the difficulties posed by the problem of crop water needs versus the availability of water resources appear. This article, based on field surveys and in-situ measurements, aims to identify the pressure of irrigation on water resources and the optimization of their use in an agricultural area, where irrigated agriculture represents 85% of the water consumption of the Zana-Gadaïne plain. The piezometric study in correlation with hydrogeological data reveals that groundwater resources are limited, aggravated by wastage resulting in a consequent drawdown of 24 meters over 11 years. The analysis of interannual climate variability has enabled us to draw rainfall maps characteristic of the evolution of rainfall over the past decades where we observe a net deficit in precipitation. We calculated the evapotranspiration and the requirements in irrigation water for each crop in order to compare them with the available hydric resources and the establishment of irrigation schedules for the principal irrigated crops. The analysis of interannual climate variability has enabled us to draw rainfall maps characteristic of the evolution of rainfall over the past decades where we observe a net deficit in precipitation. We calculated the evapotranspiration and the requirements in irrigation water for each crop in order to compare them with the available hydric resources and the establishment of irrigation schedules for the principal irrigated crops.

Considering three sites under different climate conditions (arid, semi-arid, and subhumid), this study aims to use the vadose-zone water stable isotope profiles to estimate the groundwater recharge rate. High-resolution vertical subsurface soil sampling along the vadose zone of the investigated sites was conducted. The collected samples were analysed to determine their stable isotope ratios (δ²H and δ¹⁸O) that were used along with the piston displacement method to estimate recharge. Annual recharge rates of 0.2% (± 0.1%), 2.5%, and 18% of the total annual precipitation were obtained for the arid, semi-arid, and subhumid sites, respectively. Recharge rates at the semi-arid and subhumid sites are comparable to those previously estimated using water balance-based methods. The recharge rate at the arid site is lower than that previously estimated for that site using the water budget-based method, revealing difficulties in applying the piston displacement method under an arid regime.

Stratigraphic, sedimentological and magnetic study was performed on alluvial terraces, rich in archaeological tools, the region of OUM ALI, in north-eastern Algeria. The sedimentological points of view, the sediments are dominated by the sand fraction followed by the silt fraction; moderate concentrations of CaCO3 are the result of the dissolution of the surrounding limestone reliefs (Maastrichtian limestone). The morphoscopic observation of quartz grains with a dissecting microscope allows us to offer more or less significant changes, since they are often dull or sub-blunted. The results of the magnetic survey are consistent with those of the sedimentological study. The values of magnetic susceptibility are strong in the middle part of the stratigraphic section (just above the archaeological level) and decrease slightly at the top. Lower values are stored in the lower part. The dependence of frequency values of magnetic susceptibility (fd) are strong throughout the stratigraphic section and show the presence of a mixture of single-domain grain size (R), pseudo-single domain (PMD) and superparamagnetic (SP) (with a predominance of SP grains). The high concentration of SP grain size reveals the presence of significant soil formation during the implementation of the sediment

On the southwestern Tethyan Margin of Tunisia, the well-known anoxic black shale facies of the Cenomanian-Turonian transition contrasts with oxic fossiliferous carbonates, first characterized here as lateral equivalents. In terms of sequence stratigraphy, the analysis of four wisely sampled sections in Central and Southern Tunisia led to interpret these deposits as a transgressive interval (TST). This interval spans the Whiteinella archaeocretacea Zone of foraminifera and is capped with a glauconite-rich highly bioturbated maximum flooding surface (MFS). In the reference section of Oued Bahloul and the Kalaat Senan area of North-Central Tunisia, these deposits overlay a Shelf Margin Wedge made of conglomeratic and bioclastic limestones. In South-Central and Southern Tunisia, the TST is characterized by the onset of oxic facies relaying laminated carbonates with local emergence surfaces. The analysis of both oxic and anoxic facies from the Cenomanian-Turonian transition allows identifying five successive bioevent markers, known elsewhere within the Tethyan domain: the extinction of the foraminifera genus Rotalipora (or Thomasinella), the Heterohelix shift, the Whiteinella proliferation, the filament event, and the appearance of Helvetotruncana helvetica. Among these bioevents, the Heterohelix shift coincides with the transgressive surface, while the filament event announces the maximal flooding surface. These Cenomanian-Turonian transition bioevents are of a particular relevance for regional and long-distance high-resolution correlations.

The authorities of Constantine city have been working on the redevelopment and calibration of the Rhumel and Boumerzoug wadis since 2015. The latter calebrage works caused great damage to the banks, thus affecting the Quaternary geological formations in place (alluvial terraces, flood plains). A multidisciplinary research project based on a geomorphological and sedimentological approach was quickly set up to create a scientific data base before their total destruction and loss of physical traces all along the wadis. The present study focuses on the sedimentological and geochemical analysis of the alluvial deposits of Boumerzoug wadi in order to describe the sediments, to reconstitute their nature, and to interpret both the climatic evolution and the paleo-environments of the region. Sedimentological and geochemical results confirm the succession of deposition cycles linked to progressive climate change.

The Bouteldja coastal aquifer is one of the most important groundwater resources in North eastern of Algeria. The region is under a sub-humid climate with an average rainfall of 600-880 mm/y. The unconfined aquifer is constituted of Quaternary sands formations. The hydrogeological characteristics were determined based on previous reports. A very important inflow recharges the sandy aquifer in the Southeastern boundary, in relation to a fault network system linking the aquifer and the Obeira Lake area. Another inflow is observed at the Southern boundary in relation to the exchanges with the alluvial aquifer of Bouteldja. The purpose of the present study is to provide an initial assessment of the groundwater flow and water budget of this aquifer. To achieve this goal, a one-layer groundwater flow numerical model was developed using the MODFLOW-2005 code and the FREEWAT software, using the available data. The model was run in steady state conditions. Calibration was achieved using the piezometric measurements of May 2018 as calibration target. After several trials of manual calibrations, the model successfully simulated the groundwater flows directions and heads. Calibration efforts lead to an acceptable concordance (for the purpose of this study) between the estimated and calculated hydraulic conductivity and piezometric heads, except at the Eastern border. The analyses of the simulated inflow budget shows that aside the rainfall infiltration, exchanges with surface water bodies, the adjoining alluvial aquifer and the fault system provide a relevant amount of water. This significant recharge needs additional investigations. This numerical modeling exercise using MODFLOW, the FREEWAT software and GIS reached the objective of a preliminary description of the groundwater flow and it represents an acceptable starting point for more thorough hydrodynamic characterization of the Bouteldja coastal aquifer.

This paper studies aquifer's hydrodynamic behavior by combining a flow-simulation model with transmissivity optimization (cokriging) in order to provide an optimal management scheme for the groundwater aquifer. The use of a cokriging approach improves the transmissivity data which are insufficient for the database of the groundwater flow simulation model. The obtained results are then used to model the groundwater flow of the Tebessa-Morsott shallow aquifer, located in NE Algeria, under a steady and transient regime. The results of the model calibration for the steady-state (year 2010) show that the recharge by rainfall and leakage rate are similar compared to those calculated by the analytical approach, (84,354 m³/day for the recharge and 36,986 m³/day for pumped water flow rate). The results of the transient regime show the alluvial aquifer affected by large drawdowns reaching 40 m over 20 years (year 2030 scenario) due to increase in water exploitation from pumping wells to answer water needs of the Tebessa region.

This study investigates the multiple contamination sources of a coastal Mediterranean aquifer in northeastern Algeria that is bordered by two rivers and neighboring densely populated areas. Hydrogeochemical and isotopic groundwater characterization is carried out, including the analyses of major elements, water stable isotopes δ²H-H₂O and δ¹⁸O-H₂O, and stable isotopes of nitrate δ¹⁵N-NO₃ and δ₁₈O-NO₃, and then integrated into the history of land use over the study area. Groundwater nitrate concentrations ranging from 1.6 to 235 mg/L with a median value of 69 mg/L are evidence of the degradation of groundwater quality induced by anthropogenic sources. The combined of δ¹⁵N-NO₃ and δ₁₈O-NO₃ ratios showed that nitrate in groundwater is attributable to (i) the uncontrolled development of inadequate private sanitation systems over the study area, and (ii) the unsafe application of animal manure to fertilize crops. Very active saltwater intrusion is confirmed by several hydrogeochemical indicators. Interestingly, the intrusion mechanism appears to be more complex than a direct intrusion from the Mediterranean Sea. During the high-water period, saltwater intrusion may also originate from the two rivers bordering the aquifer, via upstream migration of seawater through the river mouths. The heavier ratios in δ²H-H₂O and δ¹⁸O-H₂O of surface water collected from the rivers suggest that water from the Mediterranean Sea is mixing with water in the rivers. Multi-source contamination not only contributes to complex chemical reactions within the aquifer, but also contributes, via the cumulative effect of the various sources, to affecting large parts of the study area. The present study may serve as a warning to the effect that historical land-use practices may exert seriously deleterious impacts on groundwater quality and greatly limit conditions for the sustainable management of Mediterranean coastal areas.

The studied area, so called Chott El Gharbi shelters a multilayer aquifer system. The hydro-chemical tool shows that the results of the groundwater analyzes of the aquifer system of the Chott El Gharbi region revealed that they are sulphated-calcium and magnesian. Water infiltrated at the Bajo-Bathonian and Mio-Plio-Quaternary carbonate formations is enriched with HCO3- and SiO2 along its underground route. Also, the presence of a Triassic evaporitic formation or the Cenomano- Turonian argilo-gypsum formation enriches these waters with SO4 2- , Cl- , K+ , Mg2+, Na+ and Ca2+ . Thermodynamics has shown that these waters are under saturated evaporitic elements, which gives them a greater power of dissolution than that of carbonates which are in equilibrium or sometimes even supersaturated and tend to precipitate.