Improving the integrated hydrological simulation on a data-scarce catchment with multi-objective calibration

Qianwen He,Frank Molkenthin

doi:10.2166/hydro.2021.132

Abstract

Abstract The process-based hydrological model Soil and Water Assessment Tool ensures the simulation's reliability by calibration. Compared to the commonly applied single-objective calibration, multi-objective calibration benefits the spatial parameterization and the simulation of specific processes. However, the requirements of additional observations and the practical procedure are among the reasons to prevent the wider application of the multi-objective calibration. This study proposes to consider three groups of objectives for the calibration: multisite, multi-objective function, and multi-metric. For the study catchment with limited observations like the Yuan River Catchment (YRC) in China, the three groups corresponded to discharge from three hydrometric stations, both Nash–Sutcliffe efficiency (NSE) and inversed NSE for discharge evaluation, and MODIS global terrestrial evapotranspiration product and baseflow filtered from discharge as metrics, respectively. The applicability of two multi-objective calibration approaches, the Euclidean distance and nondominated sorting genetic algorithm II, was analyzed to calibrate the above-mentioned objectives for the YRC. Results show that multi-objective calibration has simultaneously ensured the model's better performance in terms of the spatial parameterization, the magnitude of the output time series, and the water balance components, and it also reduces the parameter and prediction uncertainty. The study thus leads to a generalized, recommended procedure for catchments with data scarcity to perform the multi-objective calibration.

Highlights

Integrated process-based hydrological models play an increasingly important role in supporting catchment management
Due to the comparably long time required for the calibration, i.e. approximately 2 min/simulation of nondominated sorting genetic algorithm II (NSGA-II) and approximately 1.5 min/ simulation of Euclidean distance (ED) or SUFI-2 for a standard PC of core i7, 4.20 GHz, and 16GB RAM, the number of simulations is a critical factor to determine the efficiency of the calibration approaches
The higher the number of the objectives is, the fewer parameter sets could theoretically be qualified. It resulted in a shorter range of parameter values of ED and NSGA-II, which might explain the less reliable validation period

Summary

Introduction

Integrated process-based hydrological models play an increasingly important role in supporting catchment management (van Griensven et al ). The classic calibration approach applied a regressionbased summary statistic (Gupta et al ) as the objective function, e.g. Nash–Sutcliffe efficiency (NSE), to optimize the goodness of fit of the output variable, e.g. the discharge at the catchment outlet. This approach is referred to as single-objective calibration if only one output variable is evaluated and it is fundamental to perform the calibration procedure. The limitations of the single-objective approach are obvious It neglects the trade-off among interactive processes and responses at the interior location of the watershed (Yen et al ), and the neglect of the catchment heterogeneity will lead to the parameters selected inconsistent with their physical meanings (Zhang et al ). Applying only one objective function tends to derive a biased assessment, e.g. NSE is more sensitive to the peak values (Krause et al ) and leads to a less reliable simulation in the low-flow period

Methods

Results

Discussion

Conclusion