Lowland catchment hydrology
Around the world, lowland areas are often densely populated and centers of economic activity and transport. The lack of topography, however, makes them vulnerable to flooding, climate change, and deterioration of water quality. Hydrological models can be used by water managers as a tool for early warning, risk assessment and infrastructure design. However, the models that are commonly used in lowland areas are often high-dimensional (groundwater or hydraulic) models. Low-dimensional models have typically been designed for use in mountainous catchments.
The title of my PhD thesis reflects the two-part research question: (1) what are the dominant catchment processes determining a lowland river's response to rainfall and (2) how can these processes be represented in simple hydrological models? For both of these questions, I focussed on topics which are important for lowland areas: (1) the relation between catchment storage and discharge, (2) the coupling between shallow groundwater and unsaturated zone, (3) activation of flowroutes at different stages of wetness and (4) the feedback between groundwater and surface water.
Wageningen Lowland Runoff Simulator (WALRUS)
The processes in the figure above have eventually been schematised to WALRUS (figure on the left). WALRUS is a novel rainfall-runoff model which explicitly accounts for processes that are important in lowland areas, notably (1) groundwater-unsaturated zone coupling, (2) wetness-dependent flow routes, (3) groundwater-surface water feedbacks and (4) seepage and surface water supply. WALRUS consists of a coupled groundwater-vadose zone reservoir, a quickflow reservoir and a surface water reservoir. WALRUS is suitable for operational use because it is computationally efficient and numerically stable (achieved with a flexible time step approach). In the open source model code default relations have been implemented, leaving only four parameters which require calibration. For research purposes, these defaults can easily be changed.
- Contribution to the courses mentioned under Education in the top right corner.
- My colleague Paul Torfs and I made a starting course for the programming environment R, called A (very) short introduction to R .
- As part of the course Water 1, students make a poster about a water-related topic from their location of origin. These posters are combined on this interactive map .
- In the MOOC (Massive Open Online Course) Sustainable Urban Development on EdX, I have a small contribution on pluvial flooding.