On 29.05.2018, an extreme flood event took place in the city of Wuppertal, which was caused by torrential rains of short duration during a heavy thunderstorm season. This led to the highest peak discharge recorded at the city of Wuppertal in the last 100 years. This episode was followed by further intense precipitation, causing two more flood events (on 07.06.2018 and on 10.06.2018) on the cities of Wuppertal, Leverkusen, and Solingen.
In the frame of BINGO and for the case study “too much water” (addressed for the Wupper research site), 23 downscaled extremal episodes provided by WP2 were simulated for the Mirke Creek, which is an important urban sub-catchment within the city of Wuppertal. Only one of the simulated extremal episodes exceeded the 100-year flood (simulated episode’s time frame: 24.06.2023 – 28.06.2023). The interpretation of WP2 data should not be based on one-to-one correspondence; rather, the use of statistical approaches for the analysis of results is recommended. Thus, a simulated exceedance of the 100-year flood threshold indicates that in the next decade, this value will be surpassed at least once - regardless of the simulated extremal episode's time frame.
For this reason, it is assumed that the simulated extremal episode which exceeded the 100-year flood corresponds to the event that took place on 29.05.2018. In conclusion, it is considered that WP2 downscaled extremal episodes captured accurately extreme precipitation events.
The extreme summer of 2018 was characterized by abnormally high temperatures (especially in July and August) and little rain. However, the precipitation in May and June 2018 was also abnormally high.
In general, the summer months in the Wupper catchment are relatively dry. Even when it rains, the vegetation “takes” almost all rainfall through interception and evapotranspiration. As a result, a dry summer alone does not lead to water scarcity issues. On account of last year’s “wet” winter (2017-2018), we are not facing water availability problems, and, as mentioned, we did have lots of precipitation in May and June.
We do face problems though, when a dry summer follows a dry winter (or several consecutive dry winters). In conclusion, the problem would really rise if from October-November to ca. middle March - middle April (i.e., winter months), it does not rain.