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 2

State variables in SWAT model chosen for correlation analysis.

Order	State variable	Description	Units	Level
1		Amount of surface runoff lagged or stored on a given day	mm	HRU
2		Amount of lateral flow lagged or stored on a given day	mm	HRU
3		Amount of water stored in shallow aquifer on a given day	mm	HRU
4		Amount of water stored in the soil layer (ly) at the end of day	mm	HRU
5		Water stored in reach at the end of day	m^3	Subbasin

Note: is the number of soil layers on profile in a hydrologic response unit (HRU).