Future changes of the terrestrial water budget over twenty major
European river catchments from CORDEX regional climate model projections
Abstract
Climate change may cause profound changes in the regional water cycle
causing negative impacts in many sectors, such as agriculture or water
resources. In this study, projected changes of the terrestrial water
cycle are investigated based on the simulations from 47 regional climate
model ensemble members of the COordinated Regional Downscaling
EXperiment (CORDEX) project’s EURO-CORDEX initiative, which downscale
different global climate models of the CMIP5 experiment over a 12km
resolution pan-European model domain. We analyze climate change impacts
on the terrestrial water budget through changes in the long-term annual
and seasonal cycles of precipitation, evapotranspiration, and runoff
over 20 major European river catchments (Guadalquivir, Guadiana, Tagus,
Douro, Ebro, Garonne, Rhone, Po, Seine, Rhine, Loire, Maas, Weser, Elbe,
Oder, Vistuala, Danube, Dniester, Dnieper, and Neman) for near
(2021-2050) and far future (2070-2099) time spans with reference to a
historical period (1971-2000) for three Representative Concentration
Pathways (RCPs), RCP2.6, RCP4.5, and RCP8.5. The analysis shows
substantial differences between the projected changes in precipitation,
evapotranspiration, and runoff for the twenty European catchments. For
the near future RCP8.5 scenario, the long-term average of the annual sum
precipitation increases over most of Europe by up to 10% in the
ensemble mean over central European catchments; but also decreases up to
10 % are found, e.g. over the Iberian Peninsula. For the far future,
the long-term average ensemble means of the annual precipitation sum
increases from 30% for eastern, 15% for central to 7% for western
European catchments, and further decreases up to 25% over the Iberian
Peninsula, which will likely cause water stress situations. These first
order changes in precipitation lead to ensuing changes in
evapotranspiration and runoff, that cause altered hydrological regimes
and feedback processes in the water cycle in the catchments.