Simulating streamflow in an ungauged catchment of Tonlesap Lake Basin in Cambodia using Soil and Water Assessment Tool (SWAT) model

Figures & data

Fig. 1 Study area: Stung Pursat River Basin.

Fig. 2 Elevation map of Stung Pursat River Basin.

Fig. 3 Landuse map of Stung Pursat River Basin.

Fig. 4 Soil type map of Stung Pursat River Basin.

Table 1 The available input data for setting SWAT model.

Data	Information	Period	Description	Source
Digital elevation model (DEM)	Raster, 30 m-resolution	–	Terrain elevation	ASTER-GDEM 2
Land use map	Raster, 250 m-resolution	2002	Land-use classification	MRC
Soil type map	Raster, 250 m-resolution	2002	Soil classification and physical properties	MRC
Meteorological data	Daily	2002–2011	Observed daily rainfall at 3 rainfall stations: Peam, Pursat and Bap Bat locate in the catchment	DHRW of MOWRAM
			Maximum and minimum temperature, humidity, sunshine hours, and wind speed data with grid of 0.25° spatial resolution	Global weather data
Flow data	Daily	2002–2011	Observed daily streamflow at Bac Trakoun Station	DHRW of MOWRAM

Table 2 The selected parameters with initial parameter ranges put into SWAT-CUP program with SUFI-2 method for the parameter sensitivity analysis.

No.	Parameter name	Description	Range		Method
			Min	Max
1	Cn2.mgt	Moisture condition II curve number	−25%	25%	Relative (1)
2	Esco.hur	Soil evaporation compensation factor	0	1	Replace (2)
3	Sol_Awc.sol	Available water capacity of the soil layer	−25%	25%	Relative (1)
4	Sol_Z.sol	Depth from soil surface to bottom of layer (mm)	0	3500	Replace (2)
5	Gwqmn.gw	Threshold water level in shallow aquifer for base flow	0	5000	Replace (2)
6	Sol_K.sol	Saturated hydraulic conductivity of first layer	0	2000	Replace (2)
7	Revapmn.gw	Threshold water level in shallow aquifer for revap	0	500	Replace (2)
8	Alpha_Bf.gw	Baseflow alpha factor	0	1	Replace (2)
9	Epco.hur	Plant uptake compensation factor	0	1	Replace (2)
10	Ch_S2.rte	Average slope of main channel	0.001	1	Replace (2)
11	Ch_N2.rte	Manning’s value for the main channel	0	0.3	Replace (2)
12	Ch_K2.rte	Effective hydraulic conductivity of main channel	0	500	Replace (2)
13	Surlag.bsn	Surface runoff lag coefficient	0	24	Replace (2)
14	GW_Revap.gw	Groundwater evapotranspiration coefficient	0.02	0.2	Replace (2)
15	GW_Delay.gw	Ground delay (days)	0	500	Replace (2)

Note: (1): Multiplying initial parameter by value in percentage; (2): replacing initial parameter by value

Table 3 Performance ratings of recommended statistics for streamflow simulation.

Performance rating	NSE	RSR	PBIAS
Unsatisfactory	NSE ≤ 0.5	RSR > 0.7	PBIAS ≥ ±25
Satisfactory	0.5 < NSE ≤ 0.65	0.6 < RSR ≤ 0.7	±15 ≤ PBIAS < ±25
Good	0.65 < NSE ≤ 0.75	0.5 < NSE ≤ 0.6	±10 ≤ PBIAS < ±15
Very good	0.75 < NSE ≤ 1	0.5 < NSE ≤ 0	PBIAS < ±10

Table 4 Most sensitive parameters for stremflow simulation in Stung Pursat River Basin.

No.	Parameter Name	Description	Rank	p-value	Range
					Min	Max
1	R__SOL_AWC.sol	Available water capacity of the soil layer	7	0.046610093	−25%	25%
2	V__ESCO.hru	Soil evaporation compensation factor	6	0.001468219	0	1
3	V__CH_N2.rte	Manning's value for the main channel	5	9.3805E-06	0	0.3
4	V__SOL_K.sol	Saturated hydraulic conductivity of first layer	4	4.42605E-11	0	2000
5	V__ALPHA_BF.gw	Baseflow alpha factor	3	5.49431E-20	0	1
6	R__CN2.mgt	Moisture condition II curve number	2	1.62439E-54	−25%	25%
7	V__CH_K2.rte	Effective hydraulic conductivity of main channel	1	5.69674E-68	0	500

Table 5 Final auto-calibration result of fitted sensitive parameters.

No.	Parameter Name	Description	Range		Fitted value
			Min	Max
1	V__SURLAG.bsn	Surface runofflag coefficient	0	24	14.330
2	R__SOL_AWC.sol	Available water capacity of the soil layer	−25%	25%	0.197
3	V__ESCO.hru	Soil evaporation compensation factor	0	1	0.693
4	V__CH_N2.rte	Manning's value for the main channel	0	0.3	0.230
5	V__SOL_K.sol	Saturated hydraulic conductivity of first layer	0	2000	161.216
6	V__ALPHA_BF.gw	Baseflow alpha factor	0	1	0.257
7	R__CN2.mgt	Moisture condition II curve number	−25%	25%	-0.371
8	V__CH_K2.rte	Effective hydraulic conductivity of main channel	0	500	369.951

Fig. 5 The hydrograph of daily simulated and observed flow for calibration period.

Fig. 6 Scatter plot of daily observed versus simulated streamflow for calibration period.

Fig. 7 The hydrograph of monthly simulated and observed flow for calibration period.

Fig. 8 Scatter plot of monthly observed versus simulated streamflow for calibration period.

Fig. 9 The hydrograph of daily simulated and observed flow for validation period.

Fig. 10 Scatter plot of daily observed versus simulated streamflow for validation period.

Fig. 11 The hydrograph of monthly simulated and observed flow for validation period.

Fig. 12 Scatter plot of monthly observed versus simulated streamflow for validation period.