Land degradation and recurrent drought are the major threats to rain-fed agriculture in the semiarid Ethiopian highlands. To reduce the risk of crop failure induced by moisture stress and to bring food self sufficiency through irrigation, water harvesting has become a priority in theGebeyehu Taye, Poesen, J., Van Wesemael, B., Vanmaercke, M., Daniel Teka, Deckers, J., Goosse, T., Maetens, W., Nyssen, J., Hallet, V., Nigussie Haregeweyn, 2013. Effects of land use, slope gradient, and soil and water conservation structures on runoff and soil loss in semi-arid northern Ethiopia. Physical Geography, 34(3), 236-259.2

Reliability and validity of groundwater analysis strongly depend on the availability of large volumes of high-quality data. Putting all data into a coherent and logical structure supported by a computing environment helps ensure validity and availability and provides a powerful tool for hydrogeological studies. A hydrogeological geographic information system (GIS) database that offers facilities for groundwater-vulnerability analysis and hydrogeological modelling has been designed in Belgium for the Walloon region. Data from five river basins, chosen for their contrasting hydrogeological characteristics, have been included in the database, and a set of applications that have been developed now allow further advances. Interest is growing in the potential for integrating GIS technology and groundwater simulation models. A "loose-coupling" tool was created between the spatial-database scheme and the groundwater numerical model interface GMS (Groundwater Modelling System). Following time and spatial queries, the hydrogeological data stored in the database can be easily used within different groundwater numerical models.Résumé La validité et la reproductibilité de l'analyse d'un aquifère dépend étroitement de la disponibilité de grandes quantités de données de très bonne qualité. Le fait de mettre toutes les données dans une structure cohérente et logique soutenue par les logiciels nécessaires aide à assurer la validité et la disponibilité et fournit un outil puissant pour les études hydrogéologiques. Une base de données pour un système d'information géographi-que (SIG) hydrogéologique qui offre toutes les facilités pour l'analyse de la vulnérabilité des eaux souterraines et la modélisation hydrogéologique a été établi en Belgique pour la région Wallonne. Les données de cinq bassins de rivières, choisis pour leurs caractéristiques hydrogéolo-giques différentes, ont été introduites dans la base de données, et un ensemble d'applications qui ont été déve-loppées permet dès maintenant de prochaines avancées. L'intérêt grandit pour le potentiel d'intégration de la technologie des SIG et les modèles de simulation des nappes. Un outil de couplage a été créé entre le schéma de base de données spatiales et l'interface GMS (GroundWater Modelling System, système de modélisation de nappe) du modèle numérique de nappe. Suivant les requêtes en fonction du temps et de l'espace, les données hydrogéologiques stockées dans la base de données peuvent être aisément utilisées dans différents modèles numériques de nappes.Resumen La fiabilidad y validez de los análisis de aguas subterráneas dependen enormemente de la disponibilidad de muchos datos de alta calidad. Integrarlos en una estructura consistente y lógica mediante un entorno informático sirve para asegurar su validez y disponibilidad, y rrepresenta una herramienta muy potente para ulteriores estudios hidrogeológicos. Se ha diseñado en la región de Valonia (Bélgica) una base de datos hidrogeológica basada en un sistema de información geográfica (GIS), con el que se dispone...

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Belonging to the family of alternative cementitious materials, inorganic polymers are rising in importance because of the drive to decrease CO 2 emissions of concrete production. A synthetic Fe-rich slag resembling industrial copper or lead slags, was mixed with a sodium silicate activating solution. 57 Fe Mössbauer spectra analyses indicate that the oxidation reactions are taking place simultaneously with the polymerization reactions. The slag contains Fe 2+ states and a small amount of Fe 3+. During polymerization a new octahedral Fe 2+ state is formed, while oxidation is manifested through the appearance of an additional Fe 3+ state. The reactions continue after setting, lowering the relative contributions of the slag in the Mössbauer and FTIR spectra of the samples. The Na + /Fe 3+ molar ratio in the mixture that makes up the binder after 28 days is ∼1, suggesting the participation of tetrahedral Fe 3+ in the silicate framework, charge balanced by Na + .

This paper presents the results of a detailed field investigation that was performed for studying groundwater recharge processes and solute downward migration mechanisms prevailing in the unsaturated zone overlying a chalk aquifer in Belgium. Various laboratory measurements were performed on core samples collected during the drilling of boreholes in the experimental site. In the field, experiments consisted of well logging, infiltration tests in the unsaturated zone, pumping tests in the saturated zone and tracer tests in both the saturated and unsaturated zones. Results show that gravitational flows govern groundwater recharge and solute migration mechanisms in the unsaturated zone. In the variably saturated chalk, the migration and retardation of solutes is strongly influenced by recharge conditions. Under intense injection conditions, solutes migrate at high speed along the partially saturated fissures, downward to the saturated zone. At the same time, they are temporarily retarded in the almost immobile water located in the chalk matrix. Under normal recharge conditions, fissures are inactive and solutes migrate slowly through the chalk matrix. Results also show that concentration dynamics in the saturated zone are related to fluctuations of groundwater levels in the aquifer. A conceptual model is proposed to explain the hydrodispersive behaviour of the variably saturated chalk. Finally, the vulnerability of the chalk to contamination issues occurring at the land surface is discussed. D