Procedure of hydrological modeling in a semi-arid river ...Ammar Rafiei . outline •Objective •Introduction •Study area •Preparation of data sets •Model parameterization •Uncertainty

Procedure of hydrological modeling in a semi-arid river basin with SWAT

By:

Ammar Rafiei

outline

• Objective

• Introduction

• Study area

• Preparation of data sets

• Model parameterization

• Uncertainty analysis

• Sensitivity analysis

• results

Objectives:

1- Building and calibrating a hydrological model in a semi arid river basin of Iran 2- Quantifying the water resources availability in the study area

Introduction

• Water scarcity in arid and semi arid area has negative impact on planning and management of this regions.

• Low precipitation , low water availability

• weakness of management

• Groundwater usage

• More than 90 % of water are using for agriculture with WUE less than 35 %

Study area

Razan-Ghavand watershed

• Watershed Area: 3100 Km2

• Max altitude 2842 m

• Min altitude: 1577 m

• Climate: semi arid

• Mean annual rainfall: 290 mm

• Mean annual temperature: 11⁰C

• Aquifer area: 1750 Km2

• Mean water level: 30 m

Study area: Razan-Ghavand

• Major river: Gharehchay river

with mean annual discharge at

the outlet: 6.68 m3s-1


• Major river: Gharehchay river with mean annual discharge at the outlet: 6.68 m3s-1

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River Discharge





• Zehtaran river with mean annual

discharge at the outlet: 0.66 m3s-1



• Zehtran river with mean annual discharge at the outlet: 0.66 m3s-1

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Discharge





• Zehtaran river with mean annual

discharge at the outlet: 0.66 m3s-1

• Sirab-khomigan river with mean

annual discharge at the outlet:

0.33 m3s-1



• Zehtaran river with mean annual discharge at the outlet: 0.66 m3s-1

• Sirab-khomigan river with mean annual discharge at the outlet: 0.33 m3s-1

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Discharge



• Zehtaran river with mean annual discharge at the outlet: 0.66 m3s-1

• Sirab-khomigan river with mean annual discharge at the outlet: 0.33 m3s-1

• Koshabad river station, outside the watershed, with mean annual discharge at the outlet: 2.25 m3s-1

Land types

Material and method

SWAT input/output

Input:

• DEM

• Landuse

• Soil

• Climate data – Daily precipitation

– Daily temperature

• Agriculture management & practice data

Output:

• Hydrological component – Groundwater recharge

– Soil moisture

– Actual evapotranspiration

• Other Components: – Crop yield

– Water quality

– Sediment

Digital elevation model

Input:

• DEM • Landuse • Soil • Climate data

– Daily precipitation



Resolution : 25 m Source: topographical map 1:25000

Hydrological component Groundwater recharge Soil moisture Actual evapotranspiration

Other Components: Crop yield Water quality Sediment

Output:

Land use map

• Landsat 2009 • Supervised classification • Overall Accuracy = 71.4317% • Kappa Coefficient = 0.6604

Input:







Output:

Soil map

• Soil layers up to 5 layers

Input:







Output:

Climate data

No of rain gage stations= 21 No of Synoptic stations=4 No. of hydrometric stations =3

Input:







Output:

No of rain gage selected: 8 ( 2 outside + 6 inside)

Agriculture management & practice

Input:







Output: • Agricultural schedule both

for rainfed and irrigated lands

Model setup DEM

15 × 15 m Landsat Derived 2009 30 × 30 m

Soil Map 1:250000

HRU

No of sub basin with inlet: 138, No. of HRU with HRU: 831

Model set up

• Model was set up with inlet with non dominate HRU,

• Type of crop : winter wheat • Auto-irrigation and fertilization operation options

were used to simulate crop growth.

• evapotranspiration method : Hargreaves method • curve number (CN) was adjusted based on the

slop

• SUFI-2 was used to calibration and validation, uncertainty and sensitivity analysis,

Duration of calibration: 2003-2008 Duration of validation: 1998-2002 Warm up duration: 2 years • 28 Parameters was used for optimization

Uncertainty analysis

optimization Parameter Definition

CN2(.mgt) SCS runoff curve number for moisture condition II

GW_DELAY(.gw) Groundwater delay time (days)

ALPHA_BF(.gw) Baseflow alpha factor (days)

REVAPMN(.gw) Threshold water in shallow aquifer

GW_REVAP(.gw) Revap coefficient

RCHRG_DP(.gw) Aquifer percolation coefficient

GWQMN(.gw) Threshold water level in shallow aq. for baseflow

SOL_AWC(.sol) Available water capacity factor

SOL_K(.sol) Saturated hydraulic conductivity

SOL_BD(.sol) Soil bulk density

SOL_ALB(.sol) Moist soil albedo

EPCO(.hru) plant uptake compensation factor

SLSUBBSN(.hru) Average slope length (m)

OV_N(.hru) Manning's n value for overland flow

CH_N2(.rte) Manning's n value for main channel

CH_K2(.rte) Effective hydraulic conductivity in main channel alluvium

ALPHA_BNK(.rte) Base flow alpha factor for bank storage (days)

SFTMP(.bsn) Snowfall temperature

SMTMP(.bsn) Snow melt base temperature (ºC)

SMFMX(.bsn) Melt factor for snow on 21 Jun

SMFMN(.bsn) Melt factor for snow on 21 Dec

TIMP(.bsn) Snow pack temperature lag factor

SURLAG(.bsn) Surface runoff lag coefficient

ESCO(.hru) Soil evaporation compensation factor

HEAT_UNITS heat unit

HI_TARG harvest index

AUTO_WSTRS Water stress

BIO_TARG bio target

Results & Discussion

Results of SWAT output

Zehtaran

Omarabad

0.00020.00040.00060.00080.000

100.000120.000140.000160.000

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Observated data

simulated data

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observated data simulated data

NS: -0.76 , PBIAS:0.12, RMSE:14.20

NS: -15.9 , PBIAS:2.9, RMSE:1.5

Choose the duration for calibration and validation

- Sirab-khomigan discharge-shows different hydrological condition in I and II periods.

I

II

Sub basins affected to flow in each station

Stations Sub basins Area(km2)

14 (Sirab khomigan) 1,2,3,4,5,6,12,13,14 255

41(Zehtaran) 23,26, 27,28,29,32, 33, 34,

37,38,41

420

71(Omarabad) All subbasin 3100

Sensitivity analysis

• Global sensitivity

• One at a time method




Parameter Name t-Stat P-Value

r__CN2.mgt________23,26,27,28,29,32,33,34,37,38,41 -34.67 0.00

r__CN2.mgt________1,2,3,4,5,6,12,13,14 -15.06 0.00

v__SMFMN.bsn -11.31 0.00

v__ALPHA_BNK.rte________1,2,3,4,5,6,12,13,14 -9.39 0.00

v__ALPHA_BNK.rte________23,26,27,28,29,32,33,34,37,38,41

-9.27 0.00

r__SOL_AWC().sol________23,26,27,28,29,32,33,34,37,38,41

7.33 0.00

v__SMFMX.bsn -4.93 0.00

v__TIMP.bsn -4.89 0.00

v__GWQMN.gw________23,26,27,28,29,32,33,34,37,38,41

2.02 0.04

V__GW_DELAY.gw________1,2,3,4,5,6,12,13,14 2.34 0.02

v__CH_K2.rte________23,26,27,28,29,32,33,34,37,38,41

2.47 0.01

r__SOL_AWC().sol________1,2,3,4,5,6,12,13,14 1.97 0.05

v__GW_REVAP.gw________23,26,27,28,29,32,33,34,37,38,41

1.78 0.07

V__GW_DELAY.gw________7-11,15-22,24,25,30,31,35,36,39,40,42-138

1.64 0.10




Calibration and validation of outlet No.71

calibration

• P-factor=0.38

• R-factor=0.78

• R2 = 0.57

• NS= 0.56

validation

• P-factor= 0.45

• R-factor= 1.02

• R2 = 0.69

• NS= 0.66


calibration validation

• P-factor= 0.51

• R-factor= 1.33

• R2 = 0.78

• NS= 0.42

• P-factor= 0.49

• R-factor= 1.76

• R2 = 0.71

• NS= 0.59


calibration

• P-factor= 0.51

• R-factor= 1.26

• R2 = 0.48

• NS= 0.35

validation

• P-factor= 0.44

• R-factor= 0.36

• R2 = 0.91

• NS= 0.72

CROP calibration

Calibration winter wheat Validation winter wheat

Irrigated: p-factor= 0.67 r-factor= 0.70 MSE = 1.08 t/ha

Rainfed: p-factor= 0.83 r-factor= 0.77 MSE = 0.07 t/ha

Irrigated: p-factor= 0.92 r-factor= 1.25 MSE = 0.19 t/ha

Rainfed: p-factor= 0.70 r-factor= 0.54 MSE = 0.25 t/ha

-Average (2003-2008) monthly 95PPU ranges of a: actual evapotranspiration b: soil water

content c:perculation d:surface runoff

Water components spatial distribution

ET Percolation Precipitation

Surface runoff Soil water

Conclusion

• Low data availability , especially amount of water use , is one of the main problem to calibrate the model.

• In semi arid regions because of low river discharge, the calibration process is pretty difficult . hence, the crop calibration can increase the precision of model.

Documents

Procedure of hydrological modeling in a semi-arid river ...Ammar Rafiei . outline •Objective •Introduction •Study area •Preparation of data sets •Model parameterization •Uncertainty