I am looking for river flow gauged data for rivers in Europe, i.e. time series.
Data can be peak flow or daily flow (m3/s) but it has to cover all of Europe's river basins.
For all of Europe, some useful links can be found at the Europe Environment Agency's Trends in monthly stream flow - Projected change in average annual and seasonal river flow - Projected change in daily average river flow
Complete Dutch data can be found from Rijkswaterstaat's Waterways page.
I found this website and it is the best solution so far: