Mass balance calibration and reservoir representations for large-scale hydrological impact studies using SWAT+
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Mass balance calibration and reservoir representations for large-scale hydrological impact studies using SWAT+ Celray James Chawanda 1
2
& Jeffrey Arnold & Wim Thiery
1,3
& Ann van Griensven
1,4
Received: 20 March 2020 / Accepted: 29 October 2020/ # The Author(s) 2020
Abstract
Climate change (CC) has a high impact on hydrological processes which calls for reliable projections of CC hydrological impacts at large scales. However, there are several challenges in hydrological modelling at large scales. Large-scale models are often not adapted and evaluated at regional scale due to high computation time requirements or lack of information on human interactions, such as dam operations and irrigation practices at local scale. In this study, we present a regionalised methodology that uses a hydrological mass balance calibration (HMBC) and global datasets to represent reservoir and irrigation practices and apply these to a SWAT+ model for Southern Africa. We evaluate the influence of HMBC and the representation on irrigation and reservoirs on model performance and climate projections. We propose a generalised implementation of reservoirs using global datasets and decision tables to represent irrigation and reservoir management. Results show that inclusion of irrigation, reservoirs and HMBC leads to improved simulation of discharge and evapotranspiration with fewer iterations than a full parameter calibration. There is a substantial difference between projections made by the regionalised model and default model when looking at local impacts. We conclude that largescale hydrological studies that involve local analysis and spatial mapping of results benefit from HMBC and representation of management practices. The proposed methodology can be scaled up and improve overall projections made by global models. Keywords SWAT+ . Hydrological modelling . Calibration . Climate change
This article is part of a Special Issue on “How evaluation of hydrological models influences results of climate impact assessment”, edited by Valentina Krysanova, Fred Hattermann and Zbigniew Kundzewicz
* Celray James Chawanda [email protected] Extended author information available on the last page of the article
Climatic Change
1 Introduction Climate and hydrological models have been used to assess seasonal and geographic patterns of water resources at the catchment-scale (Kim et al. 2008), regional-scale (Goderniaux et al. 2009) and global-scale (e.g. Yang et al. 2010; Vörösmarty et al. 2000). Although climate change is a global phenomenon, climate change impacts are primarily manifested at the regional scale (IPCC 2014) where most adaptation measures are planned and implemented (Hattermann et al. 2017). As such, developing high-quality climate impact projections at the regional scale is of key importance. Assessment of continental- and global-scale hydrological models often centres on overall model performance at the cost of model performance in individual catchments (Gosling and Arnell 2011). The models are usually applied at low spat
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