Improving the Distributed Hydrological Model Performance in Upper Huai River Basin: Using Streamflow Observations to Update the Basin States via the Ensemble Kalman Filter

Table 4

The sensitive parameters in SWAT for rainfall-runoff modeling and their standard deviation (SD) of Gaussian multiplicative error in streamflow assimilation.

Parameters	Units	Description	Level	SD of GME
CN2	—	Initial SCS runoff curve number for moisture condition II	HRU	0.05
ESCO	—	Soil evaporation compensation factor	HRU	0.2
ALPHA_BF	Days	Baseflow recession constant	HRU	0.2
GW_REVAP	—	Ground “revap” coefficient	HRU	0.2
GWQMN	mm	Threshold depth of water in the shallow aquifer required for return flow to occur	HRU	0.2
REVAPMN	mm	Threshold depth of water in the shallow aquifer for “revap” or percolation to the deep aquifer to occur	HRU	0.2
OV_N	—	Manning’s “” value for overland flow	HRU	0.1
SOL_AWC	mm/mm	Available water capacity of the soil layer	HRU	0.2
CH_N()	—	Manning’s “” values for the tributary channels	HRU	0.2
CH_N()	—	Manning’s “” values for the main channel	Subbasin	0.2
SURLAG	—	Surface runoff lag coefficient	Basin	0.2

Note: is the number of soil layers on profile in a hydrologic response unit (HRU); SD represents standard deviation; GME represents Gaussian multiplicative error.