Publications (6)10.48 Total impact
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Article: Groundwater modeling in integrated water resources management--visions for 2020.
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ABSTRACT: Groundwater modeling is undergoing a change from traditional stand-alone studies toward being an integrated part of holistic water resources management procedures. This is illustrated by the development in Denmark, where comprehensive national databases for geologic borehole data, groundwater-related geophysical data, geologic models, as well as a national groundwater-surface water model have been established and integrated to support water management. This has enhanced the benefits of using groundwater models. Based on insight gained from this Danish experience, a scientifically realistic scenario for the use of groundwater modeling in 2020 has been developed, in which groundwater models will be a part of sophisticated databases and modeling systems. The databases and numerical models will be seamlessly integrated, and the tasks of monitoring and modeling will be merged. Numerical models for atmospheric, surface water, and groundwater processes will be coupled in one integrated modeling system that can operate at a wide range of spatial scales. Furthermore, the management systems will be constructed with a focus on building credibility of model and data use among all stakeholders and on facilitating a learning process whereby data and models, as well as stakeholders' understanding of the system, are updated to currently available information. The key scientific challenges for achieving this are (1) developing new methodologies for integration of statistical and qualitative uncertainty; (2) mapping geological heterogeneity and developing scaling methodologies; (3) developing coupled model codes; and (4) developing integrated information systems, including quality assurance and uncertainty information that facilitate active stakeholder involvement and learning.Ground Water 09/2009; 48(5):633-48. · 1.78 Impact Factor -
Article: Numerical analysis of water and solute transport in variably-saturated fractured clayey till.
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ABSTRACT: This study numerically investigates the influence of initial water content and rain intensities on the preferential migration of two fluorescent tracers, Acid Yellow 7 (AY7) and Sulforhodamine B (SB), through variably-saturated fractured clayey till. The simulations are based on the numerical model HydroGeoSphere, which solves 3D variably-saturated flow and solute transport in discretely-fractured porous media. Using detailed knowledge of the matrix, fracture, and biopore properties, the numerical model is calibrated and validated against experimental high-resolution tracer images/data collected under dry and wet soil conditions and for three different rain events. The model could reproduce reasonably well the observed preferential migration of AY7 and SB through the fractured till, although it did not capture the exact depth of migration and the negligible impact of the dead-end biopores in a near-saturated matrix. A sensitivity analysis suggests fast flow mechanisms and dynamic surface coating in the biopores, and the presence of a plough pan in the till.Journal of Contaminant Hydrology 10/2008; 104(1-4):137-52. · 2.32 Impact Factor -
Article: The inadequacy of monitoring without modelling support.
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ABSTRACT: There is much to gain in joining monitoring and modelling efforts, especially in the present process of implementing the European Water Framework Directive and in the coming implementation of the Groundwater Directive. Nevertheless, present practises in the water management world suggest that most often models are not considered an option when monitoring obligations in the WFD are solved. The present paper analyses the constraints, such as perceived insufficiency of data for modelling, lack of explicit requirement for modelling in the WFD and its associated technical guidance documents, lack of awareness about what models can do and lack of confidence in models by water managers and policy makers. The findings have mainly emerged from a series of Harmoni-CA workshops aiming at bringing the monitoring and modelling communities together for a discussion of benefits and constraints in the joint use of monitoring and modelling. The workshops were attended by scientists, water managers, policy makers, stakeholders and consultants. The overall conclusion is that modelling can significantly improve the benefits of monitoring data; by quality assurance of data, interpolation and extrapolation in space and time, development of process understanding (conceptual models), and the assessment of impacts of pressures and effects of programmes of measures.Journal of Environmental Monitoring 10/2007; 9(9):931-42. · 1.99 Impact Factor -
Article: Use of Models to Support the Monitoring Requirements in the Water Framework Directive
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ABSTRACT: Implementation of the EU Water Framework Directive (WFD) poses many new challenges to European water managers. Monitoring programmes play a key role to assess the status and identify possible trends in the environmental conditions of river basins; to gain new knowledge on water processes and to assess to which extent implemented measures actually have the expected effects in terms of improving the environmental status. Despite a general acknowledgement in the scientific community on the benefits of using monitoring and modelling jointly, it has not been the common practise in the European monitoring programmes so far. Several obstacles may be identified which limits the joint use of monitoring and modelling, such as lack of the required skill, lack of time, lack of confidence in models but also a lack of awareness on how models can be used in practise. In this paper we provide examples on how modelling can support the monitoring programmes to meet the objectives of the monitoring programmes in the WFD more efficiently. The extent to which the monitoring requirements in the WFD can be expected to supply sufficient data for modelling purposes is further addressed. This question is, however, not well posed, as the data requirement for modelling is highly dependent on the required accuracy of the model results.Water Resources Management 09/2007; 21(10):1649-1672. · 2.05 Impact Factor -
Article: Fluorescence imaging applied to tracer distributions in variably saturated fractured clayey till.
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ABSTRACT: The study of mechanisms controlling preferential flow and transport in variably saturated fractured clayey till is often hindered by insufficient spatial resolution or unknown measuring volume. With the objective to study these mechanisms while circumventing the obstacles, tracer experiments with two fluorescent tracers Acid Yellow 7 (AY7) and Sulforhodamine B (SB) were performed at three different rain events for a fall and a summer season. Irrigated areas were excavated down to depths of 2.8 m and the movement of both tracers in the exposed profiles was delineated simultaneously by high spatial resolution apparent concentration maps (pixel approximately 1 mm(2)) obtained with an imaging device. The device consists of a light source and a CCD camera, both equipped with tracer-specific-filters for fluorescent light. The fluorescence images were corrected for nonuniform lighting, changing surface roughness, and varying optical properties of the soil profile. The resulting two-dimensional apparent concentration distribution profiles of the tracers showed that: (i) relative low water content in the upper 10 cm of the irrigated till in summer had a pronounced retardation effect on the AY7-migration and no effect on the SB-migration; (ii) the dead-end biopores were not activated in the fall season; (iii) only 3D fracture-plans connected to hydraulically active 1D-biopores contributed to the leaching; (iv) the tracer migration primary followed macropores during both seasons, though AY7 also followed a topsoil piston transport in summer; (v) the highest tracer pixel apparent concentrations were often found in macropores and most pronounced in the summer season; and (vi) 3D-dilution in fractures seems to play a dominating role in AY7-migration in the fall season.Journal of Environmental Quality 37(2):448-58. · 2.32 Impact Factor -
Article: Uncertainty in the environmental modelling process – A framework and guidance
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ABSTRACT: A terminology and typology of uncertainty is presented together with a framework for the modelling process, its interaction with the broader water management process and the role of uncertainty at different stages in the modelling processes. Brief reviews have been made of 14 different (partly complementary) methods commonly used in uncertainty assessment and characterisation: data uncertainty engine (DUE), error propagation equations, expert elicitation, extended peer review, inverse modelling (parameter estimation), inverse modelling (predictive uncertainty), Monte Carlo analysis, multiple model simulation, NUSAP, quality assurance, scenario analysis, sensitivity analysis, stakeholder involvement and uncertainty matrix. The applicability of these methods has been mapped according to purpose of application, stage of the modelling process and source and type of uncertainty addressed. It is concluded that uncertainty assessment is not just something to be added after the completion of the modelling work. Instead uncertainty should be seen as a red thread throughout the modelling study starting from the very beginning, where the identification and characterisation of all uncertainty sources should be performed jointly by the modeller, the water manager and the stakeholders.Environmental Modelling & Software.
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2009
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Geological Survey of Denmark and Greenland
Copenhagen, Capital Region, Denmark
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