The Use of River Flow Discharge and Sediment Load for Multi-Objective Calibration of SWAT Based on the Bayesian Inference

Abstract

The soil and water assessment tool (SWAT) is widely used to quantify the spatial and temporal patterns of sediment loads for watershed-scale management of sediment and nonpoint-source pollutants. However few studies considered the trade-off between flow and sediment objectives during model calibration processes. This study proposes a new multi-objective calibration method that incorporates both flow and sediment observed information into a likelihood function based on the Bayesian inference. For comparison, two likelihood functions, i.e., the Nash–Sutcliffe efficiency coefficient (NSE) approach that assumes model residuals follow the Gaussian distribution, and the BC-GED approach that assumes model residuals after Box–Cox transformation (BC) follow the generalized error distribution (GED), are applied for calibrating the flow and sediment parameters of SWAT with the water balance model and the variable source area concept (SWAT-WB-VSA) in the Baocun watershed, Eastern China. Compared with the single-objective method, the multi-objective approach improves the performance of sediment simulations without significantly impairing the performance of flow simulations, and reduces the uncertainty of flow parameters, especially flow concentration parameters. With the NSE approach, SWAT-WB-VSA captures extreme flood events well, but fails to mimic low values of river discharge and sediment load, possibly because the NSE approach is an informal likelihood function, and puts greater emphasis on high values. By contrast, the BC-GED approach approximates a formal likelihood function, and balances consideration of the high- and low- values. As a result, inferred results of the BC-GED method are more reasonable and consistent with the field survey results and previous related-studies. This method even discriminates the nonerodible characteristic of main channels.

Pemodelan Erosi dan Sedimentasi di DAS Bajulmati : Aplikasi Soil dan Water Assesment Tool (SWAT)

“…Data observasi sedimen tidak tersedia di lapangan, sehingga kalibrasi menggunakan data debit. Penelitian yang dilakukan oleh Cheng et al (2018), mengatakan bahwa sedimen dan beban polutan memiliki keterikatan kuat dengan debit DAS dan dapat digunakan untuk mengurangi ketidakpastian model aliran. Hasil model SWAT juga menunjukan keterikatan pengaruh sedimen dan debit sebesar 69%.…”

Evaluation of overland flow modelling hypotheses with a multi‐objective calibration using discharge and sediment data

“…Sikorska et al ( 2015 ) used a rainfall–runoff model (HydMod) with a build‐up/wash‐off model (BwMod) and shows that the multi‐objective calibration provide more reliable TSS prediction with sharper uncertainty bounds. The SWAT model has also often been used to address this question (Bekele & Nicklow, 2007 ; Brighenti et al, 2019 ; Cheng et al, 2018 ; Muleta & Nicklow, 2005 ). The results generally lead to the conclusion that simultaneous calibration helps to achieve a more robust calibration compared to sequential calibration, and this improvement is particularly observed in the prediction of suspended sediments (Brighenti et al, 2019 ; Cheng et al, 2018 ).…”

“…The SWAT model has also often been used to address this question (Bekele & Nicklow, 2007 ; Brighenti et al, 2019 ; Cheng et al, 2018 ; Muleta & Nicklow, 2005 ). The results generally lead to the conclusion that simultaneous calibration helps to achieve a more robust calibration compared to sequential calibration, and this improvement is particularly observed in the prediction of suspended sediments (Brighenti et al, 2019 ; Cheng et al, 2018 ).…”