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要旨

Robust assessments of stream-flow volume and variability under current and potential future conditions are essential for sustainable water resources planning and management. Non-linear and overlapping responses to climate, land use, and water resources management (WRM) make it difficult to link observed stream-flow variability to individual drivers and to project potential future changes in stream-flow volume and variability. Here, we investigate WRM influences on stream-flow variability for two rivers with similar natural catchment characteristics, the Schwarze Elster and the Spree. The Schwarze Elster is characterized by less intensive WRM compared to the Spree. Management influences on stream-flow variability in the past were analysed by comparing observed managed stream-flow with simulated natural flow (model SWIM). Simulation results of natural flow and managed stream-flow (model WBalMo) forced by different climate scenarios were investigated to assess management influences on potential future stream-flow. The Schwarze Elster shows little management influences on stream-flow both in the past and under future scenarios. WRM related to lignite mining activities rather than natural processes dominated seasonal and annual stream-flow variability of the Spree in the past, while reservoir management mainly impacted short-term variability. Long-term and short-term stream-flow variability of the Spree are expected to be further reduced in future by reservoir management and water transfers to ensure minimum flow requirements. Strong impacts of WRM in reducing stream-flow variability in future scenarios underline the role of reservoir management as an effective and flexible adaptation option to uncertain climate change impacts on hydrology.