Abstract
Abstract. Climate change impacts on hydrological processes should be simulated for river basins using validated models and multiple climate scenarios in order to provide reliable results for stakeholders. In the last 10–15 years, climate impact assessment has been performed for many river basins worldwide using different climate scenarios and models. However, their results are hardly comparable, and do not allow one to create a full picture of impacts and uncertainties. Therefore, a systematic intercomparison of impacts is suggested, which should be done for representative regions using state-of-the-art models. Only a few such studies have been available until now with the global-scale hydrological models, and our study is intended as a step in this direction by applying the regional-scale models. The impact assessment presented here was performed for three river basins on three continents: the Rhine in Europe, the Upper Niger in Africa and the Upper Yellow in Asia. For that, climate scenarios from five general circulation models (GCMs) and three hydrological models, HBV, SWIM and VIC, were used. Four representative concentration pathways (RCPs) covering a range of emissions and land-use change projections were included. The objectives were to analyze and compare climate impacts on future river discharge and to evaluate uncertainties from different sources. The results allow one to draw some robust conclusions, but uncertainties are large and shared differently between sources in the studied basins. Robust results in terms of trend direction and slope and changes in seasonal dynamics could be found for the Rhine basin regardless of which hydrological model or forcing GCM is used. For the Niger River, scenarios from climate models are the largest uncertainty source, providing large discrepancies in precipitation, and therefore clear projections are difficult to do. For the Upper Yellow basin, both the hydrological models and climate models contribute to uncertainty in the impacts, though an increase in high flows in the future is a robust outcome ensured by all three hydrological models.
Highlights
Setting adequate climate stabilization goals and designing appropriate adaptation policies should rely on a sound quantitative understanding of the expected impacts of climate change under different emission scenarios and different levels of global warming
After the calibration and validation of the three hydrological models, they were run for the period 1971–2099 using five general circulation models (GCMs) scenarios for four representative concentration pathways (RCPs) providing 60 time series, which were analyzed for long-term average seasonal dynamics and trends
Two examples of trends for the median flow Q50 simulated by the three hydrological models driven by the Had climate scenario and RCP8.5 are presented in Fig. 7 for the Upper Niger and Upper Yellow
Summary
Setting adequate climate stabilization goals and designing appropriate adaptation policies should rely on a sound quantitative understanding of the expected impacts of climate change under different emission scenarios and different levels of global warming. A probabilistic framework for assessing uncertainties in climate change impacts on low-flow scenarios for the River Thames considering a similar set of uncertainty sources is suggested by Wilby and Harris (2006) All these studies compare results for the regional scale, while Schewe et al (2014) performed a multi-model assessment of water scarcity under climate change by comparing results of twelve global hydrological models driven by five GCM projections. Our study is intended as a contribution to the intercomparison of climate change impacts for the water sector on the regional scale It was done for three large-scale river basins on three continents, the Rhine in Europe, the Upper Niger in Africa and the Upper Yellow River in Asia, by applying three hydrological models, SWIM (Krysanova et al, 1998), HBV (Bergström and Singh, 1995) and VIC (Liang et al, 1994), after their calibration and validation. The objectives were (a) to compare climate impacts on seasonal water discharge, (b) to compare future trends considering three runoff quantiles, Q90, Q50 and Q10, in terms of trend direction and slope, and (c) to evaluate uncertainties from different sources, namely related to climate models (CMs) providing scenarios, hydrological models (HMs) and RCPs
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