An integrated hydrological model (MOHISE) was developed in order to study the impact of climate change on the hydrological cycle in representative water basins in Belgium. This model considers most hydrological processes in a physically consistent way, more particularly groundwater flows which are modelled using a spatially distributed, finite-element approach. Thanks to this accurate numerical tool, after detailed calibration and validation, quantitative interpretations can be drawn from the groundwater model results. Considering IPCC climate change scenarios, the integrated approach was applied to evaluate the impact of climate change on the water cycle in the Geer basin in Belgium. The groundwater model is described in detail, and results are discussed in terms of climate change impact on the evolution of groundwater levels and groundwater reserves. From the modelling application on the Geer basin, it appears that, on a pluriannual basis, most tested scenarios predict a decrease in groundwater levels and reserves in relation to variations in climatic conditions. However, for this aquifer, the tested scenarios show no enhancement of the seasonal changes in groundwater levels.RØsumØ Un modle hydrologique intØgrØ (MOHISE) a ØtØ dØveloppØ afin d'Øtudier l'impact du changement climatique sur le cycle hydrologique de bassins versants reprØsentatifs de Belgique. Ce modle prend en compte tous les processus hydrologiques d'une manire physiquement consistante, plus particulirement les Øcoule-ments souterrains qui sont modØlisØs par une approche spatialement distribuØe aux ØlØments finis. Grâce à cet outil numØrique prØcis, aprs une calibration et une validation dØtaillØes, des interprØtations quantitatives peuvent Þtre rØalisØes à partir des rØsultats du modle de nappe. ConsidØrant des scØnarios de changements climatiques de l'IPCC, l'approche intØgrØe a ØtØ appliquØe pour Øvaluer l'impact du changement climatique sur le cycle de l'eau du bassin du Geer en Belgique. Le modle de nappe est dØcrit en dØtail et les rØsultats sont discutØs en terme d'impact du changement climatique sur l'Øvolution des rØserves souterraines. Les premiers rØsul-tats indiquent que des dØficits d'eau souterraine peuvent apparaître dans le futur en Belgique.Resumen Se ha desarrollado un modelo hidrológico integrado (MOHISE) para estudiar el impacto del cambio climµtico en el ciclo hidrológico de cuencas representativas en BØlgica. Este modelo considera todos los procesos hidrológicos de forma coherente, especialmente en relación con los flujos de aguas subterrµneas, que son modelados por medio de un enfoque de elementos finitos espacialmente distribuidos. Gracias a esta herramienta numØrica precisa, y tras una calibración y validación detalladas, se puede obtener interpretaciones cuantitativas de los resultados del modelo del acuífero. Considerando escenarios de cambio climµtico IPCC, se ha aplicado el enfoque integrado a la evaluación del impacto de dicho cambio climµtico en el ciclo hidrológico de la cuenca del Geer. Se describe los d...

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...

Abstract. We develop and implement the groundwater model, Saturated/Unsaturated Flow and Transport in 3D (SUFT3D), to integrate water quantity/quality data and simulations with models of other hydrologic cycle components, namely, rivers and the ocean. This work was done as part of the Sea Air Land Modeling Operational Network (SALMON) project supported by the IBM International Foundation through its Environmental Research Program. The first research steps, presented here, address the simulation of typical hydrologic conditions to demonstrate SUFT3D's effectiveness and accuracy. The theory behind the modeling of seawater intrusion and groundwater-river interaction is summarized along with the numerical methods and characteristics of SUFT3D. The code was applied to different, increasingly complex scenarios: confined to unconfined conditions, local to regional scale, homogeneous to increasing heterogeneity, two-to three-dimensional. Of particular interest were the impacts of different boundary conditions and influence of river interactions on seawater intrusion. Results are illustrated, discussed, and compared, when possible, to those in the literature. Simulating groundwater exchange between both the river and the ocean has provided interesting results that better depict the dynamics of flow and transport in coastal zone groundwater systems. IntroductionDifferent models can be developed to simulate water flow and quality at large scales in both time and space. Each part of the hydrological cycle, i.e., ocean, surface water, groundwater, and atmosphere, is simulated using models adapted to each particular component. Usually, each model is designed for only one part of the water cycle, and interactions with other parts are taken into account by using prescribed input/output flux at the boundaries. This is commonly considered as satisfactory so that groundwater, river, and ocean models are usually connected only by these prescribed boundary conditions. How- The averaged momentum balance equation can be reduced to the linear Darcy's law for an aquifer. This is appropriate

Calibration of ground water transport models is often performed using results of field tracer experiments. However, little attention is usually paid to the influence, on resulting breakthrough curves, of injection conditions and well-aquifer interactions, more particularly of the influence of the possible trapping of the tracer in the injection wellbore. Recently, a new mathematical and numerical approach has been developed to model injection conditions and well-aquifer interactions in a very accurate way. Using an analytical solution derived from this model, a detailed analysis is made of the evolution of the tracer input function in the aquifer. By varying injection conditions from one simulation to another, synthetic breakthrough curves are generated with the SUFT3D ground water flow and transport finite-element simulator. These tests show clearly that the shape of the breakthrough curves can be dramatically affected by injection conditions. Using generated breakthrough curves as ''actual'' field results, a calibration of hydrodispersive parameters is performed, neglecting the influence of injection conditions. This shows that neglecting the influence of actual injection conditions can lead to (1) errors on fitted parameters and (2) misleading identification of the active transport processes. Conclusions and guidelines are drawn in terms of proposed methodologies for better controlling the tracer injection in the field, in order to minimize risk of misinterpretation of results.