University of Twente Student Theses


Modelling surface water and groundwater interactions at the Catchment of the Beurzerbeek with a coupled Tygron and MODFLOW model

Schoonderwoerd, L.M. (2022) Modelling surface water and groundwater interactions at the Catchment of the Beurzerbeek with a coupled Tygron and MODFLOW model.

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Abstract:This study investigates whether the dynamics in groundwater levels can accurately be modelled in a new coupling of the groundwater model MODFLOW and surface water model Tygron for Tygron can model surface runoff and is fast and MODFLOW can calculate the groundwater flow through various and multiple ground layers. To this end, a case study was carried out over four periods in the catchment of the Beurzerbeek. In addition, this research maps the strengths and weaknesses of this coupling. Climate change in the Netherlands is noticeable in recent years for the summers have become increasingly warm and dry, and the winters wetter. Particularly on high sandy soils, such as around the Beurzerbeek near Winterswijk in the east of the Netherlands, the water is drained too quickly, and streams can run dry. This is partly due to the high permeability of the sand, but also the layout of the areas, the rainwater is quickly drained via ditches, streams, and drainage pipes. A detailed model in which all hydrological processes are included could map the effects of various measures to retain water longer in dry areas. The research is divided into two parts. First, the coupling, a program that controls and links the groundwater model and the surface water model, written in the Python programming language, is investigated and improved. For this purpose, the influence of precipitation and the possible evapotranspiration, which according to literature are the two largest variables that influence groundwater storage, are investigated on the groundwater storage in Tygron, the model that calculates the surface water. It has been concluded that these two variables do indeed have a considerable influence on groundwater storage and that this is very time-dependent, especially for precipitation. For example, when precipitation falls within one hour, instead of spreading over 24 hours at other locations, it ends up in groundwater storage. This is because Tygron can model surface runoff, unlike many other models. The research showed that the calculated groundwater replenishment is sensitive to the intensity of weather data and because the calculation times will increase considerably, the models are linked daily while the hourly data from the KNMI are used as input. In short, Tygron calculates the groundwater replenishment after one day. This is then passed on to the MODFLOW groundwater model, which calculates the groundwater levels. These groundwater levels are then passed back to Tygron. In the second part of the study, the oscillations in the modelled groundwater levels of the coupling were compared to measured groundwater levels from the drinking water company Vitens and modelled groundwater levels in the groundwater model AMIGO of the Rijn and IJssel waterboard. The research shows that AMIGO is able to model a closer approximation of the groundwater levels than the new coupling. In addition, the maps with groundwater levels show that the model gives unreliable results for one period. Nevertheless, there are still many opportunities for the coupled model to improve. Only with more improvements and more extensive testing can it be concluded whether this model can be accurate for all hydrological processes.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Programme:Civil Engineering BSc (56952)
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