Author(s): Patrick Nistahl; Tim Muller; Gunter Meon

Linked Author(s): Tim Müller, Gunter Meon

Keywords: Climate change adaption; Reservoir planning; Hydrological impact modelling

Abstract: Projected climate change impacts on water resource systems show a high urgency for adaption measures. Especially for large scale constructions with long planning and construction phases - such as new reservoirs - a design that is based solely on observed discharge time series can lead to considerable over- or undersizing. In order to include climate change effects into the planning process, often a multiplier based on hydrological impact studies is used. In the case of multi-functional and interconnected reservoirs, this approach is not suitable due to partially conflicting operation goals. In this ongoing study, we present a methodology that combines state of the art hydrological modelling of climate change impacts with the optimized planning of new reservoirs and constructional updates of existing reservoirs. For this purpose, a model chain is used that includes an ensemble of bias-corrected regional climate models (RCMs), a semi-distributed hydrological catchment model, a numerical reservoir operation model and 2D hydrodynamic models. The model chain is applied to the region of the Western Harz mountain range (Lower Saxony, Germany) and its directly affected downstream area. Here, in total six partially interconnected reservoirs serve the system services flood protection, drinking water supply, energy generation and low water augmentation. Supplementary constructional variants to support the reliability of the existing system in a changing climate are analyzed by implementing them in the described models. The simulation of the RCM ensemble allows a direct analysis of the mitigation of climate change impacts on relevant performance criteria like, e.g., flood damage, water supply reliability, drought resilience. Moreover, the non-linear translation of climate model uncertainties into the relevant performance criteria are analyzed. First exemplary results show that an additional pumped storage plant of about 16 hm³ connected to an existing reservoir of about 47 hm³ can contribute to significantly mitigate a projected increase of flood hazard in downstream settlements. At the same time it can increase the reliability of the drinking water supply and decrease the number and duration of low water events. The combination of a wide range of different hydrological projections with four partially conflicting operation goals leads to a challenging dissemination of results to policy makers and requires an innovative optimization scheme. One possible solution is a lexicographic optimization based on externally defined rankings of operation goals.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221814

Year: 2022