This research has focussed on the differences between German and Dutch discharge measurements of the river Vecht. A cross-border comparison is carried out to see what methods and locations are used for the discharge measurements on the border of both countries and to see which factors contribute to the differences in the discharge data when the Dutch and German discharge data is compared
Cross-border discharge measurements in the river Vecht; the effect of two different methods and locations on discharge measurements
Discharge measurements at the German – Dutch border are carried out by both countries separately and in a different way. For over 15 years now, differences in the discharge data of both countries have been observed but have also been ignored. These differences can, especially during peak discharge develop into differences of 40 % of the actual discharge measured. In these cases generally the German discharge measurements are lower than the Dutch measurements. Since 2010 waterboard Vechtstromen (the Netherlands) has been developing a flood forecasting model to predict future discharge peaks on the river Vecht. This model, a Flood Early Warning System (FEWS) called FEWS Vecht has recently been calibrated and validated. However, the differences in the discharge data of the two countries made this process problematic. This study analyses the differences in the discharge data by analysing the different methods as well as the locations that are used in the two countries. Especially the Dutch measurement location, called de Haandrik is a very interesting location to measure the discharge. Just before location de Haandrik two canals cross the river Vecht which can have a significant effect on the discharge measurements of de Haandrik. Discharge measurements at de Haandrik are carried out by using a horizontal Acoustic Doppler Current Profiler (H-ADCP). The German measurement location is underneath the bridge that crosses the river Vecht at Emlichheim. Measurements are carried out by using a method generally accepted and applied throughout Germany called “Eta verfahren”. This method implies a Q-h relation that is corrected for a variable channel bed resistance by monthly measurements. Comparing the discharge data of both countries proved to be difficult due to lacking data. However the data that was available showed a large influence of the canals on the discharge measurements at de Haandrik, as well as the method used at the Haandrik to be sub-optimal for the location.