Drought trends in the Rhine and Meuse basins - Extension of the study "Regional differentiation in climate change induced drought trends in the Netherlands"

Motivated by the extreme drought conditions experienced in the 
Netherlands in 2018, trends in low discharge events for both the 
Rhine and Meuse rivers are explored, as well as drivers influencing 
discharge. The change in intensity between 1900 and 2018 of three 
drought-related variables that influence discharge (precipitation, 
temperature and potential evaporation) is studied using multiple 
observational and model data sets, with quantities averaged over 
April to September for the Rhine and Meuse basins. 

Synthesizing observational and model results, no significant change 
in precipitation intensity is found, with comparable outcome and 
confidence range for both basins. For temperature, a significant 
positive intensification results, with a best estimate lying between 
+1.5 and +2 K, for both the Rhine and the Meuse. For potential 
evaporation, observational and model estimates do not overlap and 
therefore no synthesized value for the attribution to climate change 
is given. However, both types of data point to an increase in 
intensity, with models indicating an intensity change of at least 3%.

Observed trends in discharge show a decrease for the Rhine 
(Lobith) of -9% (95% confidence interval, CI, of -19 to 3%) which 
is significant at p=0.1. For the Meuse (Monsin/Eijsden) we find a 
negative trend of -30% (95% CI -45 to -13%), which is significant 
at p=0.05. However, these observed discharge series are also subject 
to local changes not related to climate change.

The study is related to a 2020 publication that focussed on drought related trends in the Netherlands alone