Water (flow) and solute transport
Modelling of the hydrological cycle is carried out for estimations on quantity and quality of the freshwater resource, and assessment of uncertainties in these estimates.
The tasks range from detailed small-scale process studies within a single medium, such as the saturated or unsaturated part of the groundwater system, to integrated catchment scale modelling including the entire groundwater and surface water system. The tasks are grouped within the following categories:
- Freshwater resource
- Transport of contaminants
- Quality assurance and uncertainty assessments
- Remote sensing for spatial estimation of hydrological parameters on large scales.
The freshwater resource.
Traditionally, hydrological modelling has been carried out for individual domains of the hydrological system, such as the groundwater or surface water systems. The challenges we face, however, require an integrated approach in which all freshwater system components must be considered concurrently.
Integrated catchment scale modelling, including scaling issues and methods for upscaling from point and small-scale measurements to large-scale modelling, are central research topics for GEUS. The National Water Resources Model (DK-model) is an integrated surface water and groundwater model developed for the entire country for evaluating the freshwater resource at the national level. The model is utilised in Danish groundwater management (implementing the WFD in Denmark) and has served as foundation for a number of investigative studies.
The EU Water Framework Directive instructs individual member states to monitor the entire freshwater resource and to document the reliability of the established monitoring programs. This impose new challenges with a need for closer interaction between monitoring and modelling in order to better utilize monitoring as well as remote sensing data, and understanding of the freshwater resource.
Reactive transport modelling of nutrients and xenobiotic compounds is carried out for the saturated as well as unsaturated groundwater zones. Special emphasis is put on contamination from diffuse sources, such as fertilizers and pesticides, as they present the main threat to the freshwater quality in Denmark.
Vulnerability to pesticide leaching is studied on national as well as EU scales, while other projects focus on climate change effects on future pesticide leaching in Denmark. Modelling of solute transport at catchment scale presents a specific challenge. Based on DK-modelsimulations to describe the general groundwater flow, studies are carried out to estimate nitrate transport and reduction in the groundwater zone at national scale.
Quality assurance and uncertainty assessments.
In recent years, quality assurance and uncertainty assessment related to hydrological modelling have received increasing focus both nationally and internationally. GEUS has developed a national guideline on groundwater modelling, and, at the EU level, GEUS has contributed to the development of a modelling guideline. Additionally, GEUS regularly participates in modelling studies as independent reviewer.
In uncertainty analyses of model results, parameter uncertainty has traditionally been in focus. Via national, international and Ph.D. projects, GEUS has contributed to a strengthened focus on uncertainty as related to the conceptual model, including the geological conceptualisation.
Remote sensing for spatial estimation of hydrological parameters on large scales.
Satellite images are used to estimate the spatial distribution of different hydrological variables primarily for the integration of distributed hydrological models. Time series of remote sensing estimates of e.g. vegetation and albedo for parameterisation of the models while hydrological state variables and fluxes as surface temperature and evaporation is used for spatial validation and calibration of the hydrological model simulations. Especially last component is central in the part of GEUS' research which addressesa fundamentally new approach to the evaluation of spatial models.
Current projects (in alphabetic order):
- DK-model. The Danish National Water Resources Model for assessment of the overall flow conditions and water balance as wells as groundwater exploitation on regional and national scale. Contact: Anker Lajer Højberg.
- HOBE. Multidisciplinary hydrological observatorium. Contact: Torben O. Sonnenborg or Simon Stisen.
- NiCA. Nitrate reduction in a geological heterogeneous catchment. Contact: Jens Christian Refsgaard.
- Soils2Sea. Reducing nutrient loadings from agricultural soils to the Baltic Sea via groundwater and streams. Contact: Jens Christian Refsgaard.
- SPACE. Use of Remote sensing data for spatial calibration of hydrological models. Contact: Simon Stisen.
- TReNDS: Transport and Redution of Nitratet in Danish landscapes at various Scales. Contakt: Anker Lajer Højberg.
- River Basin Management Plans. Further development and use of the DK-model for the next generation of Danish RBMP. Contact: Anker Lajer Højberg).
- Water4Coast. Assessment of hydrological barriers for controlling saline water intrusion in coastal areas under a changed climate. Contact: Klaus Hinsby.