Table 2 Applied watershed model (SWAT) parameters and its range, adjusted value, and description.

Streamflow

Base flow

ALPHA_BH

0–1

0.48

Baseflow alpha factor

Day

GW_DELAY

0–500

273.5

Groundwater delay

Day

GW_REVAP

0.02

− 0.2

0.06

Groundwater re-evaporation coefficient

–

Surface runoff

CN2

35–98

0.76 times

Initial SCS runoff curve number for moisture condition

–

CH_N1

0.01

− 30

0.06

Manning's n value for tributary channel

–

SOL_AWC

0–1

0.99 times

Available water capacity of the soil layer

–

Lateral flow

ESCO

0–1

0.01

Soil evaporation compensation factor

–

EPCO

0–1

0.09

Plant uptake compensation factor

–

Water temperature

Water temperature

Slope

0.79

0.79

Slope of the regression equation between water temperature and air temperature

–

Intercept

7.89

7.89

Intercept of the regression equation between water temperature and air temperature

–

Dissolved oxygen

Total nitrogen (TN)

BC1

0.1–1

0.78

Rate constant for biological oxidation of NH4 to NO2 in the reach at 20 °C

1/day

BC2

0.2–2

1.79

Rate constant for biological oxidation of NO2 to NO3 in the reach at 20 °C

1/day

BC3

0.2

− 0.4

0.27

Rate constant for hydrolysis of organic N to NH4 in the reach at 20 °C

1/day

RS4

0.001

− 0.1

0.08

Rate coefficient for organic N settling in the reach at 20 °C

1/day

Total phosphorus (TP)

BC4

0.01

− 0.7

0.21

Rate constant for mineralization of organic P to dissolved P in the reach at 20 °C

1/day

RS5

0.001

− 0.1

0.03

Organic phosphorus settling rate in the reach at 20 °C

1/day

Dissolved oxygen (DO)

RK1

0.02

− 3.4

0.02

Carbonaceous biological oxygen demand deoxygenation rate coefficient in the reach at 20 °C

1/day

RK2

0–100

97.7

Oxygen reaeration rate in accordance with Fickian diffusion in the reach at 20 °C

1/day

Al3

1.4

− 1.8

1.62

Rate of oxygen production per unit algal photosynthesis

–

Al4

1.6

− 2.3

2.04

Rate of oxygen uptake per unit algal respiration

–