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Article

Copula-Based Infilling Methods for Daily Suspended Sediment Loads

Department of Hydraulic and Ocean Engineering, National Cheng Kung University, Tainan 701, Taiwan
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Author to whom correspondence should be addressed.
Academic Editor: Anargiros I. Delis
Water 2021, 13(12), 1701; https://doi.org/10.3390/w13121701
Received: 4 May 2021 / Revised: 10 June 2021 / Accepted: 16 June 2021 / Published: 19 June 2021
(This article belongs to the Section Hydrology)
Less-frequent and inadequate sampling of sediment data has negatively impacted the long and continuous records required for the design and operation of hydraulic facilities. This data-scarcity problem is often found in most river basins of Taiwan. This study aims to propose a parsimonious probabilistic model based on copulas to infill daily suspended sediment loads using streamflow discharge. A copula-based bivariate distribution model of sediment and discharge of the paired recorded data is constructed first. The conditional distribution of sediment load given observed discharge is used to provide probabilistic estimation of sediment loads. In addition, four different methods based on the derived conditional distribution of sediment load are used to give single-value estimations. The obtained outcomes of these methods associated with the results of the traditional sediment rating curve are compared with recorded data and evaluated in terms of root mean square error (RMSE), mean absolute percentage error (MAPE), Nash-Sutcliffe efficiency (NSE), and modified Nash-Sutcliffe efficiency (MNSE). The proposed approach is applied to the Janshou station located in eastern Taiwan with recorded daily data for the period of 1960–2019. The results indicate that the infilled sediments by the sediment rating curve exhibit better performance in RMSE and NSE, while the copula-based methods outperform in MAPE and MNSE. Additionally, the infilled sediments by the copula-based methods preserve scattered characteristics of observed sediment-discharge relationships and exhibit similar frequency distributions to that of recorded sediment data. View Full-Text
Keywords: infilling missing data; copula; suspended sediment load; conditional distribution; sediment rating curve infilling missing data; copula; suspended sediment load; conditional distribution; sediment rating curve
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MDPI and ACS Style

Shiau, J.-T.; Lien, Y.-C. Copula-Based Infilling Methods for Daily Suspended Sediment Loads. Water 2021, 13, 1701. https://doi.org/10.3390/w13121701

AMA Style

Shiau J-T, Lien Y-C. Copula-Based Infilling Methods for Daily Suspended Sediment Loads. Water. 2021; 13(12):1701. https://doi.org/10.3390/w13121701

Chicago/Turabian Style

Shiau, Jenq-Tzong, and Yu-Cheng Lien. 2021. "Copula-Based Infilling Methods for Daily Suspended Sediment Loads" Water 13, no. 12: 1701. https://doi.org/10.3390/w13121701

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