Hydrological impacts of climate change on small ungauged catchments – results from a global climate model–regional climate model–hydrologic model chain

摘要

Climate change is one of the greatest threats currently facing theworld's environment. In Norway, a change in climate will strongly affect thepattern, frequency, and magnitudes of stream flows. However, it ischallenging to quantify to what extent the change will affect the flowpatterns and floods from small rural catchments due to the unavailabilityor inadequacy of hydro-meteorological data for the calibration ofhydrological models and due to the tailoring of methods to a small-scale level. Toprovide meaningful climate impact studies at the level of small catchments,it is therefore beneficial to use high-spatial- and high-temporal-resolutionclimate projections as input to a high-resolution hydrological model. Inthis study, we used such a model chain to assess the impacts of climatechange on the flow patterns and frequency of floods in small ungauged ruralcatchments in western Norway. We used a new high-resolution regional climateprojection, with improved performance regarding the precipitationdistribution, and a regionalized hydrological model (distance distributiondynamics) between a reference period?(1981–2011) and a future period?(2070–2100). The flow-duration curves for all study catchments show more wet periods in the future than during the reference period. The results also show that in the future period, the mean annual flow increases by 16 % to 33 %. The mean annual maximum floods increase by 29 % to 38 %, and floods of 2-?to 200-year return periods increase by 16 % to 43 %. The results are based on the RCP8.5 scenario from a single climate model simulation tailored to the Bergen region in western Norway, and the results should be interpreted in this context. The results should therefore be seen in consideration of other scenarios for the region to address theuncertainty. Nevertheless, the study increases our knowledge and understanding of the hydrological impacts of climate change on smallcatchments in the Bergen area in the western part of Norway.