The new ZukoWa project is aimed at sustainable water management for municipal water suppliers.

Even though the Black Forest is known as the ‘water tower’ of south-west Germany, past years of drought have already resulted in alarmingly low spring discharges

Particularly in the drought year of 2018 and after several subsequent very dry years, the general public also realised that climate change could jeopardise the water supply in many regions of Germany during periods of drought, which was previously thought to be secure. Scientific studies in south-west Germany show an increase in rapidly developing droughts, so-called ‘flash droughts’ as well as reduced runoff in rivers and groundwater recharge. It may come as a surprise that the issue of water scarcity and quality also plays a role in the Black Forest, as the Grindenkamm in the northern Black Forest is one of the regions in Germany with the highest levels of precipitation, along with some regions in the Bavarian Alps. The German Weather Service (DWD) station at Ruhestein is one of around 10 out of several thousand stations in Germany that record an annual average of more than 2000 mm of precipitation. By comparison, only 1/3 to 1/4 of this amount is recorded in the Upper Rhine Valley. Nevertheless, the spring discharges in some administrative communities in the northern Black Forest have decreased in some of the recent drought years, in some cases to an unprecedented extent. In turn, heavy rainfall events lead to natural contamination of the springs, meaning that they cannot be used at times. As part of the joint project ‘Sustainable water management of municipal water suppliers in times of climate change (ZuKoWa)’, funded by the BMBF for three years from 1 April 2025, in which universities, municipal water suppliers and private companies are working together with Black Forest municipalities, a package of methods and measures is to be co-developed and implemented operationally using the example of the spring water supply in the Central Black Forest in Bühl, Bad Peterstal-Grießbach, Nordrach, Oberharmersbach and Zell am Harmersbach. These municipalities ensure the water supply for almost 16,000 inhabitants.

Figure 1: DWD operated rain gauge at Ruhestein. The average value is approx. 2000 mm/year. In the drought years 2018 and 2022, only 1552 and 1881 mm were recorded respectively. In 2022, July was extremely dry there with 13 mm (Photo: A. Fink)

As part of ZuKoWa, the Institute of Applied Geosciences (PD Dr. E. Eiche) at KIT is carrying out chemical analyses of the water quality. Together with the KIT Institute for Meteorology and Climate Research - Troposphere (IMKTRO) and the Institute for Environmental Sciences and Geography at the University of Potsdam, up to 8 weather stations will be set up in the study area - both in open areas and in vegetation. The aim is to improve the monitoring of precipitation. This will also be achieved by quality-checking the high-resolution operational RADOLAN precipitation product of the DWD with rain collector data in the region that is not used for its calibration. The new project stations and those of other operators are used for this purpose. In addition, high-resolution meteorological model simulations will be used to further improve the spatial and intensity distributions of precipitation in the study region. IMKTRO will provide waterworks operators with a forecasting module to allow for early warning of  extreme events and droughts as well as projections of precipitation and drought frequencies over the coming decades. ‘The monitoring and forecasting products are to be installed at the waterworks operators and thus contribute to sustainable water management for municipal water suppliers,’ says Prof Andreas Fink, one of the project leaders at IMKTRO. ‘In terms of climate projections, we can draw on many years of experience and the latest generation of climate models, which can, for example, resolve small-scale heavy precipitation over the Black Forest,’ says Prof Joaquim Pinto, the other project leader at IMKTRO.

Figure 2: At the beginning of August 2022, many streams in the upper reaches of the very wet northern Black Forest had dried up, as here at Roter Schliff (Photo: A. Fink)

ZukoWa pursues a transdisciplinary approach that does justice to the complexity of the problems in municipal water supply. The results are to be tested for their transferability to other regions such as the Allgäu and the Harz. The overall project is being coordinated by Prof St Norra from the University of Potsdam

 

Working groups: Regional Climate and Weather Hazards and Tropical Meteorology