How evaluation of global hydrological models can help to improve credibility of river discharge projections under climat
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How evaluation of global hydrological models can help to improve credibility of river discharge projections under climate change Valentina Krysanova, et al. [full author details at the end of the article] Received: 9 January 2020 / Accepted: 17 August 2020/ # The Author(s) 2020
Abstract
Importance of evaluation of global hydrological models (gHMs) before doing climate impact assessment was underlined in several studies. The main objective of this study is to evaluate the performance of six gHMs in simulating observed discharge for a set of 57 large catchments applying common metrics with thresholds for the monthly and seasonal dynamics and summarize them estimating an aggregated index of model performance for each model in each basin. One model showed a good performance, and other five showed a weak or poor performance in most of the basins. In 15 catchments, evaluation results of all models were poor. The model evaluation was supplemented by climate impact assessment for a subset of 12 representative catchments using (1) usual ensemble mean approach and (2) weighted mean approach based on model performance, and the outcomes were compared. The comparison of impacts in terms of mean monthly and mean annual discharges using two approaches has shown that in four basins, differences were negligible or small, and in eight catchments, differences in mean monthly, mean annual discharge or both were moderate to large. The spreads were notably decreased in most cases when the second method was applied. It can be concluded that for improving credibility of projections, the model evaluation and application of the weighted mean approach could be recommended, especially if the mean monthly (seasonal) impacts are of interest, whereas the ensemble mean approach could be applied for projecting the mean annual changes. The calibration of gHMs could improve their performance and, consequently, the credibility of projections. Keywords Climate change . Global hydrological models . River discharge projections . Model evaluation . Model performance . Model weighting . Credibility of projections
1 Introduction The projection of climate change impacts on river discharge is usually done by following a modelling chain, starting with several scenarios of future radiative forcing (representative Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10584-02002840-0) contains supplementary material, which is available to authorized users.
Climatic Change
concentration pathways, RCPs). After that, climate projections generated by general circulation models (GCMs) or regional climate models are collected, and often, statistical bias correction methods are applied. Then, hydrological impact models are driven by climate scenarios under certain RCPs to perform impact assessment. Nowadays, it is common to apply not only ensembles of climate scenarios from several models but also ensembles of hydrological models (HM) in such studies (e.g. Haddeland et al. 2014; Roudier et al. 2016; Gosling et al. 2017; V
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