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.

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 addresses the characterization of the Continental Intercalaire aquifer (CI) in the Tinrhert-East area of Illizi Basin on the Algerian-Libyan border, which belongs to the SASS1 system, one of the biggest transboundary aquifers in the world. This study concerns a superficies of 4 300 km2. On the basis of Mud Logging borehole data conducted in this part of the aquifer, a realistic characterization of the aquifer was done. The thickness of the CI aquifer varies from 300 m in the south to 700 m in the north, and the depth ranges from 180 m to 320 m. The interpretation of the logs showed that the aquifer is characterized by a maximum net thickness in its southwestern part (more than 600 m), the porosity is very high, ranging from 30% in the west to 24% at the Libyan borders, the permeability is low to medium around 10-5 m/s, and the maximum transmissivity values of about 8×10-3 m2/s were recorded at the center of the study area. The depth of water varies from 235 m to 312 m, and the water flows from south to north, in accordance with the general direction observed in the CI aquifer in the Northern Sahara Aquifer System (SASS). The porosity values obtained from the interpretation of the sonic and density logs permit to estimate the water reserves of this aquifer considered fossil, at thresholds much higher than what was considered until now.

Timgad Basin is a part of the North-East Algerian Saharan Atlas. It is located at the northern of the Aurès Mountain. It is bordered in the North by Bou Arif, Amrane and Tagratine mountains, while in the South it is limited by Chelia, Rdam and Nerdi Bouhmar mountains. It is shaped as a synclinal gutter oriented East-West and covers an area of about 1000 Km2 . The climate is semi-arid (cold winter and hot summer) with average annual rainfall not exceeding 350 mm. The basin is composed by varied lithology, showing large folded structures down sloping towards the center, which favor groundwater storage. The Miocene sandstone aquifer is the most important. It is characterized by a wavy shape, which form series of shale-marl filling depressions. Recent wells drilled in the basin edges and center, put in evidence its artesian character. The piezometric survey shows a groundwater convergent flow oriented towards the basin east (Bou el Freis), likewise the sandstone aquifer is marked by the presence of a West-East drainage axis which separates the basin northern part characterized by a low reservoirs hydraulic capacity from the southern part distinguished by the groundwater relative abundance.

The basin of Timgad belongs to the North-Eastern Algerian Saharan Atlas; it is located at the northern extension of the Aures Mountains. The basin is an asymmetrical syncline oriented East-West covering an area of 1000 Km2. The climate is semi-arid (cold winter and hot summer) with average annual rainfall not exceeding 400 mm. Recently, the increasing agricultural activities led to an excessive exploitation of groundwater resources. In order to meet this rising water supply demands, implementing a water resources management policy is a priority which should be based on a basin hydrogeological study. Effectively, the geological and geophysical studies have confirmed the presence of permeable Miocene and Cretaceous formations (sandstone and carbonate); relatively resistant affected by fractures network, which are probably forming a confined aquifers. Indeed, recent wells drilled in the basin center and their boundaries; show that the aquifers are artesian. The sandstone aquifer of the Miocene is the most important, it is characterized by significant thickness which can exceed 200m, its extension as well as its particular corrugated geometry, characterized by a wavy shape, which forming a series of shale-marl filling depressions, influences the groundwater flow, actually, the piezometric surface illustrates groundwater convergent flow oriented to the east, towards Bou el freis, likewise the sandstone aquifer is marked by the presence of a West-East drainage axis which separates the basin northern part characterized by a low reservoirs hydraulic capacity from the southern part distinguished by the groundwater relative abundance. Groundwater is generally easily extracted, except the northern part of the basin where the top shale-marl layer is thickens to over 1000m.