Fourteen parameters for hydrology and sediment simulation (Table 1) were calibrated utilizing root mean squared error (RMSE) and relative error as objective functions, respectively. The calibrated model provided good monthly runoff and sediment load predictions for the entire simulation period of 6 years from 1990 to 1995 with Nash–Sutcliffe efficiency coefficients of 0.60 and 0.58 and coefficient of determination of 0.83 and 0.79, respectively. The parameters are described and calibrated values shown in Table 1.

Table 1

Parameters of HYSTAR and their calibrated values

ProcessParameterDescriptionFeatureRangeCalibrated value
Direct runoff CNF Curve number scale factor Spatial scale factor 0.5–1.5 1.094 
MNO Manning's roughness coefficient scale factor for overland areas Spatial scale factor 0.5–1.5 1.054 
MNC Manning's roughness coefficient scale factor for channel Spatial scale factor 0.5–1.5 1.171 
THA Threshold area that defines initiation points of channel networks Unit: ha 1–100 17.91 
Soil moisture GCL Coefficient L of the van Genuchten equation – 0.25–0.75 0.662 
GCM Coefficient M of the van Genuchten equation – 0.25–0.75 0.325 
BCC Basal crop coefficient scale factor Spatial scale factor 0.5–1.5 0.512 
EFS Effective fraction of soil surface covered by vegetation scale factor Spatial scale factor 0.5–1.5 1.187 
RZD Root zone depth scale factor Spatial scale factor 0.1–2.0 0.339 
SAR Soil anisotropy ratio – 0.1–2.0 0.164 
Sediment transport CSO Critical Shields parameter for overland flow – 0.1–10.0 0.744 
CSC Critical Shields parameter for channel flow – 0.035–2.0 0.057 
SDR Soil detachability ratio scale factor Spatial scale factor 0.1–2.0 0.891 
SCR Soil cohesion ratio scale factor Spatial scale factor 0.1–2.0 1.066 
ProcessParameterDescriptionFeatureRangeCalibrated value
Direct runoff CNF Curve number scale factor Spatial scale factor 0.5–1.5 1.094 
MNO Manning's roughness coefficient scale factor for overland areas Spatial scale factor 0.5–1.5 1.054 
MNC Manning's roughness coefficient scale factor for channel Spatial scale factor 0.5–1.5 1.171 
THA Threshold area that defines initiation points of channel networks Unit: ha 1–100 17.91 
Soil moisture GCL Coefficient L of the van Genuchten equation – 0.25–0.75 0.662 
GCM Coefficient M of the van Genuchten equation – 0.25–0.75 0.325 
BCC Basal crop coefficient scale factor Spatial scale factor 0.5–1.5 0.512 
EFS Effective fraction of soil surface covered by vegetation scale factor Spatial scale factor 0.5–1.5 1.187 
RZD Root zone depth scale factor Spatial scale factor 0.1–2.0 0.339 
SAR Soil anisotropy ratio – 0.1–2.0 0.164 
Sediment transport CSO Critical Shields parameter for overland flow – 0.1–10.0 0.744 
CSC Critical Shields parameter for channel flow – 0.035–2.0 0.057 
SDR Soil detachability ratio scale factor Spatial scale factor 0.1–2.0 0.891 
SCR Soil cohesion ratio scale factor Spatial scale factor 0.1–2.0 1.066 

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