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Opacity

River Runoff

Key messages:

  • Changes in runoff follow changes in precipitation
  • Annual mean runoff increases roughly north of 45°N
  • Increases in runoff are greatest in Winter

Why is the content of this map important?

The river runoff is the amount of water entering local rivers and the discharge is the accumulation of all upstream runoff. Both variables are essential for making projections of floods, low flow and salt intrusion.

Which sectors are affected by this result?

River runoff affects inland navigation, as well as hydropower potential and the availability of cooling water for thermo-electric power plants.

What is shown on the maps?

As an initial approximation, the spatial pattern of the change in mean annual runoff mimics that of the change in precipitation. Thus, increases occur roughly north of 45°N. In most regions between 40 and 70% of the increase in precipitation flows into the river network. The ensemble mean reaches maximum values of the increase in runoff of about 0.2 mm/day in parts of the Alps and Norway. Increases are greatest in Winter, especially in North and North-East Europe, and in the Alps where they partially exceed 0.3 mm/day. This is due to an increase in the precipitation rate and also the fact that in higher temperatures less of the precipitation falls as snow.

Details and further information:

The maps of annual mean runoff during the reference period show that the spatial distribution of runoff resembles that of precipitation. Outside the precipitation-rich mountain ranges much of the precipitation is lost by evapotranspiration, especially in large parts of East Europe and Spain, where the generation of runoff is less than 0.3 mm/day. A considerable part of Europe’s river runoff and discharge derives from the major mountain ranges, where in large parts runoff exceeds 3 mm/day.

Additional information:

To investigate this, the ensemble of five hydrological models (E-HYPE, Lisflood, LPJmL, VIC and WBM) has been driven by the ensemble of the five mandatory climate simulations. Hence, the ensemble consists of 25 simulations in total.

The calculations are carried out and displayed only for the grid points where the output of all hydrological models is available.

Author:

Wouter Greuell

Wageningen Universiteit (WU), Netherlands