Abstract
Abstract. This study analyses how temperature-driven changes in evaporation and snow processes influence the discharge in the Rhine Basin. Using an efficient distributed hydrological model at high spatio-temporal resolution, we performed two experiments to understand how changes in temperature affect the discharge. In the first experiment, we compared two 10-year periods (1980s and 2010s) to determine how changes in discharge can be related to changes in evaporation, snowfall, melt from snow and ice, and precipitation. By simulating these periods, we can exchange the forcing components (evaporation, temperature for snowfall and melt, and precipitation), to quantify their individual and combined effects on the discharge. Around half of the observed changes could be explained by the changes induced by temperature effects on snowfall and melt (10 %), temperature effects on evaporation (16 %), and precipitation (19 %), showing that temperature-driven changes in evaporation and snow (26 %) are larger than the precipitation-driven changes (19 %). The remaining 55 % was driven by the interaction of these variables: e.g. the type of precipitation (interaction between temperature and precipitation) or the amount of generated runoff (interaction between evaporation and precipitation). In the second experiment we exclude the effect of precipitation and run scenarios with realistically increased temperatures. These simulations show that discharge is generally expected to decrease due to the positive effect of temperature on (potential) evaporation. However, more liquid precipitation and different melt dynamics from snow and ice can slightly offset this reduction in discharge. Earlier snowmelt leaves less snowpack available to melt during spring, when it historically melts, and amplifies the discharge reduction caused by the enhanced evaporation. These results are tested over a range of rooting depths. This study shows how the combined effects of temperature-driven changes affect discharge. With many basins around the world depending on meltwater, a correct understanding of these changes and their interaction is vital.
Highlights
Over the last decades, global temperatures have increased considerably (Stocker et al, 2013)
Temperature, evaporation, and precipitation substantially changed from the 1980s to the 2010s in the Rhine Basin, reflecting changes that are typical for many larger basins around the world
In the 2010s, basin average temperature was more than 1 ◦C higher, potential evaporation was almost 70 mm higher, and precipitation decreased with 80 mm
Summary
Global temperatures have increased considerably (Stocker et al, 2013). As increased temperatures affect water availability in large river systems in two important ways, it is vital to understand their effects and interactions. Higher temperatures affect the cryosphere: there will be less precipitation falling as snow, and there is more energy available to enhance melt from snow and ice. As snow stores are depleted earlier in the year, it affects the timing of the snowmelt peak in the discharge signal (Jenicek and Ledvinka, 2020; Beniston et al, 2018; Baraer et al, 2012; Huss, 2011; Hidalgo et al, 2009; Collins, 2008; Takala et al, 2009). Since meltwater from “water towers” is vital for billions of people (Viviroli et al, 2007), it is important to have a correct understanding of the expected changes in the cryosphere. Higher temperatures lead to increased potential evaporation rates, since a warmer atmosphere accommodates higher transport rates
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
