Guideline for Groundwater Resource Management Using the GIS Tools in Arid to Semi Arid Climate Regions

International audienceFood security emerged as an issue in the first decade of the 21st Century, questioning the sustainability of thehuman race, which is inevitably related directly to the agricultural water management that has multifaceteddimensions and requires interdisciplinary expertise in order to be dealt with

Hydrogeochemical and stable isotope data of Groundwater of a multi-aquifer system: Northern Gafsa basin - Central Tunisia

The hydrodynamic of the multi-aquifer system (the Continental Intercalaire “ C.I ” and the Complex Terminal “ C.T ”) of the North Gafsa basin is largely determined by tectonics (Tebessa - Gafsa fault). The composition of groundwater is controlled by complex reactions at gas-liquid-solid “mineralogical composition of associated rocks” interfaces, which depend on the natural surrounding and potential anthropogenic impact. The hydrochemical data (major ion geochemistry) indicate that these groundwaters are characterized by the dominance a Ca-Mg-HCO3/SO4 and Na-Cl-NO3 water types. Geochemical pattern is mainly controlled by the dissolution of halite, gypsum and/or anhydrite as well as by the incongruent dissolution of carbonate minerals. The pH of these samples range from 6.54 to 8.89, supporting the conclusion that the H2CO3/HCO3 couple control pH buffering. Oxygen-18 (δ18O‰SMOW) and deuterium (dD‰SMOW) isotopic data show the exchange between the groundwater and the rock (water-rock interaction) and the evaporation effect. The isotopic content of the boreholes waters is of mixed Mediterranean - Atlantic origin and is opposite to the quantity of rainwater distribution, both in space and time in the study area. This is due to its geographical situation in the southern and south-western of the Mediterranean Sea and between the Atlas area and the Sahara Platform. The concentrations of the isotopic composition of the groundwater are significantly higher than the rainwater. This is indicative of the dissolution of salts and other processes modifying the rainwater geochemical composition during infiltration into the vadose zone. The hydraulic interconnection of these components of the system has led to the evolution of these interesting groundwater types

Application of Analytical Hierarchy Process and Frequency Ratio Model for Predictive Flood Susceptibility Mapping Using GIS for the Khazir River Basin, Northern Iraq

Flood damage assessment is considered the essential tool for evaluating risk to civil and agricultural systems in land use planning. The validity of the studies’ outcome depends on the availability of data and their spatial distribution. The present study came to compute flood susceptibility maps utilizing two application models: (i) the frequency ratio, and (ii) the analytical hierarchy process. These models were then tested in the Khazir River basin using GIS with a selection of twelve flood conditioning factors. The flood inventory variables layer and flood-causing factors were created using remote sensing data, a digital elevation model, and secondary data from various sources. Then, the flood inventory map was highlight divided into training and test data, with 105 flood sites (70%) used for training and 45 sites (30%) used for testing. After applying the areas under the curve for the frequency ratio and analytical hierarchy process models, which were 90.6% and 88.9%, respectively, the final flood sensitivity maps showed similar results for the two models, which confirm the effectiveness of the adopted methodology. The study found a considerable spatial variance in flood sensitivity maps, as (21.06%) of the flooded areas are classified as having very low sensitivity to flooding, (24.09%) are classified as having low vulnerability to floods, and (23.79%) are classified as having moderate vulnerability, (24.10%) classified as highly vulnerable to flooding, and (6.96%) classified as highly vulnerable to flooding. Flood danger ranged from very low in mountain locations to very high in plain areas close to the riverbanks. Obtained results could be improved if a land-use planning policy will be applied, in order to establish a master plan for water resources development to avoid flood damage

Transfert hydraulique entre les aquifères profonds du sillon des Chotts, sud-ouest tunisien

L'étude du transfert hydraulique entre les aquifères profonds du Complexe Terminal (CT) et le Continental Intercalaire (CI) dans les régions situées au sillon des Chotts (Kébilli et Tozeur) a été menée dans ce présent travail par l'application de plusieurs approches axées sur l'hydrogéologie, l'hydrochimie et l'isotopie. L'examen des profils piézométriques effectués récemment prouvent l'existence d'un échange inter-aquifère ascendant du CI vers le CT probablement due à un réseau de failles très développé dans le secteur étudié. Le taux de mélange est estimé entre 57 % et 73 % par la méthode du Chlore et entre 57 % et 65 % par la méthode enthalpique, respectivement dans les régions de Tozeur et Kébilli. En outre, l'étude de la relation entre les teneurs en oxygène-18 et/ou en deutérium en fonction des concentrations en chlorure a permis de confirmer le déroulement du processus de mélange qui est plus prononcé dans la région de Tozeur que dans la région de Kébilli

The consequences of saline irrigation treatments on soil physicochemical characteristics

When saline water is used to irrigate crops in arid environments, appropriate irrigation management should be applied to avoid negatively impacting soil characteristics. In this study, the effects of irrigating date palms with saline water (2.24 g l−1) on soil physicochemical characteristics such as the electrical conductivity (ECe), the pH of the saturated soil paste (pHe), the concentrations of soluble cations (Ca2+, Mg2+, Na+), the sodium adsorption ratio (SAR), the saturated soil hydraulic conductivity (Ks), and the volumetric water content of the soil (θv) were evaluated in a Tunisian Saharan cropland, the Dergine Oasis, during a 4-year period (2012–2015). The effects of three different irrigation treatments of date palms on soil properties were investigated: low treatment (90% of the net irrigation requirement (NIR) of date palms was applied); medium treatment (100% of NIR was applied), and high treatment (110% of NIR was applied). The results showed that the application of saline water for irrigation inevitably has a negative impact on the physicochemical properties of the soil. Irrigation with saline water was observed to have severe negative impacts on the soil characteristics, especially ECe, Na+, Ks, and θv. However, among the three irrigation treatments applied, statistical analysis (Duncan’s multiple range test) indicated that the high treatment significantly (p < 0.05) minimized the degradation of soil characteristics by the saline water; this treatment decreased ECe, Na+, and SAR and increased the water content, θv, of the studied soil

Mise en évidence de l'origine de la thermalité et de la minéralisation des eaux géothermales de Gabes sud, Sud-est tunisien

L'évaluation des ressources hydrothermales de la région de Gabès Sud nécessite principalement la bonne connaissance des données géologiques et géophysiques, ainsi que la répartition des caractéristiques des eaux, de la température de l'hydrodynamisme des réservoirs et de leurs caractéristiques pétrophysiques. Les études géologiques, hydrogéologiques, géochimiques et géothermométriques constituent un outil adéquat pour la délimitation des bassins hydrogéothermiques. Le traitement intégré de toutes les données existantes ou nouvellement acquises, est en faveur de l'origine profonde des eaux thermales de la région de Gabès Sud et de leur résurgence au niveau de la source de Zarat par un drainage ascensionnel à travers les dysharmonies tectoniques, affectant les niveaux gréso-carbonatés du Crétacé inférieur, reconnus comme réservoir hydrothermal potentiel. La région d'étude est caractérisée par une émergence thermale remarquable avec une température de 37°C et une salinité de 2.5 g/l. Elle est marquée par une structure faillée en horsts et grabens pouvant encaisser des réserves importantes en eau thermale. Vu la parfaite similitude des caractéristiques hydrogéologiques et hydrochimiques des eaux de la source thermale et celles des forages captant le Sénonien inférieur (T° entre 24 et 31.8 °C), on a toujours rattaché cette source au Sénonien inférieur. Cependant, et suite aux premiers résultats de l'approche hydrogéothermique, il a été possible de rattacher la source aux grès et sables du Continental Intercalaire, situés à 1950 m de profondeur, et d'esquisser le modèle de fonctionnement hydrodynamique du système aquifère de Gabès sud. En effet, les eaux thermales de la source de Zarat représentent un mélange d'eau chaude profonde et d'eau froide superficielle