Abstract
Human activity has a profound influence on river discharges, hydrological extremes and water-related hazards. In this study, we compare the results of five state-of-the-art global hydrological models (GHMs) with observations to examine the role of human impact parameterizations (HIP) in the simulation of mean, high- and low-flows. The analysis is performed for 471 gauging stations across the globe for the period 1971–2010. We find that the inclusion of HIP improves the performance of the GHMs, both in managed and near-natural catchments. For near-natural catchments, the improvement in performance results from improvements in incoming discharges from upstream managed catchments. This finding is robust across the GHMs, although the level of improvement and the reasons for it vary greatly. The inclusion of HIP leads to a significant decrease in the bias of the long-term mean monthly discharge in 36%–73% of the studied catchments, and an improvement in the modeled hydrological variability in 31%–74% of the studied catchments. Including HIP in the GHMs also leads to an improvement in the simulation of hydrological extremes, compared to when HIP is excluded. Whilst the inclusion of HIP leads to decreases in the simulated high-flows, it can lead to either increases or decreases in the low-flows. This is due to the relative importance of the timing of return flows and reservoir operations as well as their associated uncertainties. Even with the inclusion of HIP, we find that the model performance is still not optimal. This highlights the need for further research linking human management and hydrological domains, especially in those areas in which human impacts are dominant. The large variation in performance between GHMs, regions and performance indicators, calls for a careful selection of GHMs, model components and evaluation metrics in future model applications.
Highlights
Human activities have a profound influence on river discharge, hydrological extremes, and waterrelated hazards, like flooding, droughts, water scarcity, and water quality issues (Van Loon et al., 2016; Liu et al,. 2017; Padowski et al, 2015; Veldkamp et al, 2017; Wada et al, 2011; Winsemius et al, 2016)
Including the parameterizations of human impacts in the global hydrological models (GHMs) leads to a large improvement in overall model performance
Hydrological performance under the human impact parameterizations (HIP) simulations shows a significant improvement compared to the NOHIP simulations for between 40.8% and 72.3% of the land area studied, depending on the GHM
Summary
Human activities have a profound influence on river discharge, hydrological extremes, and waterrelated hazards, like flooding, droughts, water scarcity, and water quality issues (Van Loon et al., 2016; Liu et al,. 2017; Padowski et al, 2015; Veldkamp et al, 2017; Wada et al, 2011; Winsemius et al, 2016). Cri pt GHMs are widely used in scientific studies They have been used to assess the historical and future impacts of socioeconomic developments and/or hydro-climatic variability and change, on freshwater resources, droughts, and water scarcity (Biemans et al, 2011; Döll et al, 2009; Döll and Müller Schmied, 2012; Fujimori et al, 2017; Gosling et al, 2017; Haddeland et al, 2006, 2007, 2014; Hanasaki et al, 2013; Van Huijgevoort et al, 2013; Kummu et al, 2016; Müller Schmied et al, 2016; Munia et al, 2016; Rost et al, 2008; Veldkamp et al, 2015a,b, 2016, 2017, Wada et al, 2011, 2013a,b, 2014a, Wanders et al, 2015). GHMs have provided input into a multitude of high-level policy documents, such as: UN
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