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

Abstract

Abstract. Climate change is one of the greatest threats currently facing the world's environment. In Norway, a change in climate will strongly affect the pattern, frequency, and magnitudes of stream flows. However, it is challenging to quantify to what extent the change will affect the flow patterns and floods from small rural catchments due to the unavailability or inadequacy of hydro-meteorological data for the calibration of hydrological models and due to the tailoring of methods to a small-scale level. To provide meaningful climate impact studies at the level of small catchments, it is therefore beneficial to use high-spatial- and high-temporal-resolution climate projections as input to a high-resolution hydrological model. In this study, we used such a model chain to assess the impacts of climate change on the flow patterns and frequency of floods in small ungauged rural catchments in western Norway. We used a new high-resolution regional climate projection, with improved performance regarding the precipitation distribution, and a regionalized hydrological model (distance distribution dynamics) 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 the uncertainty. Nevertheless, the study increases our knowledge and understanding of the hydrological impacts of climate change on small catchments in the Bergen area in the western part of Norway.

Nordic contributions to stochastic methods in hydrology

“…In Lawrence (2020), it is shown that for Norway the expected change is linked to the flood generating processes, where a decrease in flood size can be expected in several inland catchments, where snow melt is the main flood generating process, whereas increase in flood sizes is expected in catchments where rain is the main flood generating process. Particularly in small catchments, an increase in flood sizes is expected (Tsegaw et al 2020). Similar results are shown in Sweden (Bergström et al 2012), Finland (Veijalainen et al 2010) and the Baltic countries (Meilutyte-Barauskienėet al…”

Diurnal cycle of surface energy fluxes in high mountain terrain: High‐resolution fully coupled atmosphere‐hydrology modelling and impact of lateral flow

“…Being driven by atmospheric lateral boundary only, the simulation of hydrometeorological variables in WRF‐Hydro inherits the uncertainties and biases from atmospheric modelling. Using a model chain from bias‐corrected high‐resolution dynamical downscaling to terrestrial hydrological modelling, or jointly assimilating available observations in WRF‐Hydro modelling can improve the simulation of surface energy flux (e.g., Abbaszadeh et al, 2020; Tsegaw et al, 2020). Additionally, the hydrological parameter optimization also restricts the coupled WRF‐Hydro simulation, as the model calibration remains processed with adjusting conceptualized scaling factors of the most dominant parameters via offline simulations (Yucel et al, 2015; Zhang et al, 2019).…”

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“…Streamflow prediction in ungauged basins plays key role for water resources planning and environmental managements [22,23]. Reliable streamflow data contains valuable information for various purposes, including environmental impact assessment, estimation of hydrologic extremes, low-flow estimation, design of hydraulic structures, and water resources planning [24].…”