University of Twente Student Theses


Combining satellite-based et time series with integrated modeling of a wetland

Ngabo, Jean Leonce (2021) Combining satellite-based et time series with integrated modeling of a wetland.

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Abstract:Aamsveen, a fen wetland located to the South-East of Enschede, on the border of Netherlands and Germany. It is considered a recreational area and people frequently visit the area due to the aesthetic view of different vegetation species present in the area. Heath, grass, evergreen, and deciduous trees are the predominant vegetation of the wetland. The surface and groundwater interactions play a key role in the hydrology of the wetland. Different studies have been carried out in the region to analyze the interactions between the surface and groundwater such as a previous one by Emmanuel (2019). The aim of this research is to develop a method that integrates satellite-based ET time series in integrated groundwater modelling using the example of Aamsveen. It was achieved by improving the existing integrated groundwater model of Aamsveen by defining the spatial and temporal distributaion of the potential evapotranspiration (ETp) which was not perfectly considered in the previous wetland model (Emmanuel’s model). Two different methods that provide ETp (satellite-based ETp and Kc-based ETp) were adopted and compared to each other to define which one is suitable for improving the current wetland model. Besides, a new approach to calibrate and validate the wetland model was developed and applied. The approach consisted of integrating satellite-based actual evapotranspiration (ETa ) in the calibration and validation. It was done by matching the simulated ETa that includes interception to the satellite-based ETa for a calibration period of 4 years (1st January 2012 to 31st December 2015). Then the model was validated from 1st January 2016 to 31st December 2018 using also satellite-based ETa. This new method was additional to the normal calibration method with state variables (groundwater heads and streamflow) which was used in the Emmanuel’s model. A comparison of the Emmanuel’s model and the current model was carried out. The results demonstrated that satellite-based ETp (MOD16A2) time series values after bias correction were in the same range as kc-based ETp with an R2 of 0.95 and RMSE of 0.8 mm. However, in terms of representing the spatial variability of Aamsveen, Kc-based ETp was showing more details than the MOD16A2 product. Therefore, Kc-based ETp data were used in the wetland model. In the calibration, the simulated ETa plus canopy interception was matched to MOD16A2 ETa with an R2 of 0.84 and RMSE of 0.0005. The comparison of both models (the current model and Emmanuel’s model) showed that the highest outflow component from the area is ETa although the rates are different. The ETa plus interception in the Emmanuel’s model was 63.2% of rainfall (P) while in the present model, ETa with interception is 56.2% of P in the same calibration period (1st January 2012 to 31st December 2015).
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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