Quantifying and predicting river-aquifer exchange in lowland floodplains (Nete, Demer and Dijle)

Lu Min

Promoter

Huysmans Marijke, (KULeuven), Marijke.Huysmans@ees.kuleuven.be

SCK•CEN Mentor

Gedeon Matej
matej.gedeon@sckcen.be
+32 14 33 31 22

Expert group

Engineered and Geosystems Analysis

PhD started

2017-11-01

Short project description

Many of the eco-hydrological functions of floodplains are strongly related to the interactions between the floodplain's shallow groundwater (GW) and the surface water (SW) of the usually well-connected lowland rivers. The interactions between groundwater and surface water and the resulting exchange fluxes are often characterized by a high temporal and spatial variability. Combining spatially and temporally resolved field or laboratory data with physically based numerical models to identify key dynamics and to improve process understanding is an area of active research. Over the past 15 years, progress has been made in measuring groundwater/surface fluxes while recent studies point out the need for combining multiple measurement methods in order to quantify GW-SW interaction fluxes. Models that can accurately represent floodplain hydrological processes have large potential in the assessment and management of these areas in light of e.g. climate change, land use and land cover change, etc.… Coupling several components of the water cycle in order to introduce more realism in the simulation of water exchange terms between all subdomains and hence reduce model uncertainty is the gold standard in catchment-scale hydrological modelling studies. The current generation of numerical surface water and groundwater models typically uses streamflow and groundwater heads as quantitative state variable observations of the hydro(geo)logical system. This limited amount of quantitative inverse conditioning data makes the models poorly constrained and large prediction uncertainties are prevalent. This necessitates the use of alternative state variables such as heat, hydrochemistry and isotopic tracers.

Objective

The overall aim is to develop a nested-scale floodplain hydrological model, consisting of a calibrated coupled surface water-groundwater model. Subsequently, the application of the floodplain hydrological model will show how the hydrological status of the floodplain may change through changes in channel morphology (through bank seepage), climate change, land cover change, urbanisation, and local floodplain management actions (e.g. blocking of drainage channels). Both intra-annual as well as inter-annual changes in groundwater level in floodplains will be simulated.

Several specific tasks/objectives can be identified: (1) Measuring groundwater-surface water interactions; (2) Developing a coupled groundwater-surface water model at the regional and nested scale; (3) Advanced uncertainty quantification and calibration using alternative state variables; (4) Scenario-based modelling of future floodplain hydrology.