Hydrological impacts of climate change on small ungauged catchments-results from a GCM-RCM-hydrologic model chain

Abstract

Abstract. Climate change is one of the greatest threats to the World's environment. In Norway, the change will strongly affect the pattern, frequency and magnitudes of stream flows. However, it is highly challenging to quantify to what extent it will affect flow patterns and floods from small ungauged rural catchments due to unavailability or inadequacy of hydro-meteorological data for the calibration of hydrological models and tailoring methods to a small-scale level. To provide meaningful climate impact studies at small catchments, it is therefore beneficial to use high spatial and temporal resolution climate projections as input to a high-resolution hydrological model. Here we use such a model chain to assess the impacts of climate change on flow patterns and frequency of floods in small ungauged rural catchments in western Norway using a new high-resolution regional climate projection, with improved performance with regards to the precipitation distribution, and the regionalized hydrological model (Distance Distribution Dynamics) between the reference period (1981–2011) and a future period (2071–2100). The FDCs of all study catchments show there will be more wetter periods in the future than the reference period. The results also show that in the future period, the mean annual flow increases by 16.5 % to 33.3 %, and there will be an increase in the mean autumn, mean winter and mean spring flows ranging from 4.3 % to 256.3 %. The mean summer flow decreases by 7.2 % to 35.2 %. The mean annual maximum floods increase by 28.9 % to 38.3 %, and floods of 2 to 200 years return periods increase by 16.1 % to 42.7 %. The findings of this study could be of practical use to regional decision-makers if considered alongside other previous and future findings.