TY  - JOUR
A1  - van Tiel, Marit
A1  - Weiler, Markus
A1  - Freudiger, Daphné
A1  - Moretti, Greta
A1  - Kohn, Irene
A1  - Gerlinger, Kai
A1  - Stahl, Kerstin
T1  - Melting Alpine Water Towers Aggravate Downstream Low Flows: A Stress‐Test Storyline Approach
Y1  - 2023-03-27
VL  - 11
IS  - 3
JF  - Earth's Future
DO  - 10.1029/2022EF003408
PB  - 
N2  - Droughts can lead to extreme low flow situations in rivers, with resulting severe impacts. Upstream snow and ice melt in many of the world's mountain water towers can alleviate the hydrological consequences of drought, yet global warming threatens the cryosphere. To improve the understanding of melt water contributions during drought in the case of future glacier retreat, we developed stress‐test storyline scenarios to model streamflow and tested them in the European river Rhine basin. Meteorological conditions of past drought and low flow years in Europe, 1976, 2003, and 2018, were repeated at three future moments in time, representing nowadays, near future and far future conditions. The latter two conditions were obtained by climate projections under the RCP8.5 scenario. Results show that the low flow situations caused by the meteorological drought situations aggravate in future conditions, more so for the far future and for the year 2003 because of the relatively large glacier ice melt contribution in the past. Summer (July–September) streamflow may decline by 5%–25% far downstream and 30%–70% upstream and the duration of extreme low flow situations may double compared to the selected past drought events. These results are relevant for the Rhine as a major European river but stand exemplary for many other river basins and highlight the importance of cryospheric changes for downstream low flow situations in a changing climate. The stress‐test scenarios allow a glimpse into future extreme low flow events aiding adaptation planning, and might be adapted to include other important low flow drivers.
N2  - Plain Language Summary: Extended periods with strongly reduced rainfall, in combination with hot summers, lead to accumulating water shortages. As a result, water levels in rivers drop which causes problems, e.g., for shipping, cooling of power plants and drinking and irrigation water supply. During such drought periods, melt water from snow and ice is important for water supply. However, glaciers are projected to further decline in a warming climate, possibly worsen future low flow situations. To quantify this effect, we modeled the amount of water flowing through the Rhine basin (a) for past low flow events in 1976, 2003, and 2018 and (b) for hypothetical situations where we repeat the weather data of those past low flow years at three moments in the future. The results show that flows upstream and downstream in the river Rhine would get even lower in future conditions and cause low flow situations to lengthen considerably. Especially for the year 2003, which had high ice melt contributions in the past, changes are large. In summer, the flow during already critical low flow situations may decrease by up to 70% upstream, and by up to 30% downstream. The results show a glimpse into future low flow events and may help adaptation planning.
N2  - Key Points: A model framework for the Rhine basin was developed to simulate streamflow during extreme past drought years in future conditions. Extreme low flows as in 1976, 2003, and 2018 would aggravate in a future with declined glacier cover and snow pack. Repeating the drought and heatwave of 2003 in the future results in largest reductions in summer streamflow (70% upstream, 30% downstream).
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/11148
ER  -