Thinking Flood and Drought protection together

A joint potential study of CEDIM and LUBW revealed that existing flood retention basins in Baden-Württemberg could be repurposed for joint flood and drought protection.

Climate change, as manifested in Germany and Baden-Württemberg in the form of prolonged drought and water scarcity, poses significant economic and environmental risks. The recent droughts of 2018-2020 and 2022 are among the most severe in Germany's recent history, leading, among other things, to a substantial increase in the need for agricultural irrigation. Between 2009 and 2022, the irrigated arable land in Baden-Württemberg increased by 61%, and this need is likely to rise further in the future.

In this context, the KIT Institute for Water and Environment, Department of Hydrology (IWU-HYD), investigated the possibilities for expanding the use of existing reservoirs in Baden-Württemberg as part of a research project funded by CEDIM and the Landesanstalt für Umwelt Baden-Württemberg LUBW. To date, reservoirs – especially small and medium-sized ones – have primarily been built and operated for flood control. The research project examined the simultaneous use of dams for flood, heat, and drought protection using thirty representative examples.

The main results are:

  • If the water retained in the reservoirs is used to augment low water levels during periods of water shortage, up to seventy percent of water shortage situations could be resolved at many reservoirs without compromising their flood protection function.
  • If the water retained in the reservoirs is used for agricultural irrigation in a 25 km² region around the reservoir, the entire irrigation demand could be met at two-thirds of the reservoirs without compromising their flood protection function.
  • If storage control is based on real-world conditions, i.e., decisions are made based on weather and inflow forecasts, the uncertainty of these forecasts leads to a lower, but still significant, effectiveness of the reservoirs. Nevertheless, seven reservoirs were still able to compensate for more than 70% of the water shortage when used for low-water augmentation, and for agricultural irrigation this was the case for even 17 reservoirs.

Further information:
Ho, S. Q.-G., Ehret, U. (2025): Is drought protection possible without compromising flood protection? Estimating the potential dual-use benefit of small flood reservoirs in southern Germany, Hydrol. Earth Syst. Sci., 29, 2785–2810, https://doi.org/10.5194/hess-29-2785-2025.

Fig. 1: Typical flood retention basin in Baden-Württemberg.

Associated institute at KIT: KIT-Institute for Water and Environment (IWU)
Autors: Sarah Quynh-Giang Ho & Uwe Ehret (Dezember 2025)