Build and calibration of SWAT

model in basin-wide watershed

Majid Fereidoon

Design Point

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Department of Geotechnology and Geohydraulics

University of Kassel

Which Model Should be Used?

It Depends on:

– What time scale are you working at?

– What hydrologic quantity are you trying to

obtain?

– What data do you have for your watershed?

– How fast of a computer do you have?

Conceptual Model of Watershed Modeling

Typical Input

• Topography

• Soil Characteristics

• Land cover

• Land use

• Meteorological data

Typical Output

• Streamflow

• Subsurface Flow

• Depth to water table

Steps to Hydrologic Modeling

1. Delineate watershed

2. Obtain hydrologic and geographic data

3. Select modeling approach

4. Calibrate/Verify model

5. Use model for assessment/prediction/design

6. Climate Change assessment

What is a Watershed? Area that topographically contributes to the

drainage to a point of interest

Natural Watershed

Points of Interest

• Road crossing

• Stream gage

• Reservoir inlet

• Wastewater treatment plant

• Location of stream restoration

Basis for Many Hydrologic Models

Hydrologic Budget (In – Out = ΔStorage)

Watershed

Precipitation (P) Groundwater in (GWin)

Evaporation (E)

Transpiration (T) Streamflow (Q)

Groundwater out (GWout)

Reservoir

Infiltration (I)

(P + GWin) – (E + T + I + GWout + Q) = ΔStoragereservoir

Balance Equation

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SWAT Soil & water Assessment Tool

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SWAT (Soil and Water Assessment Tool) is a

comprehensive, semi-distributed river basin

model that requires a large number of input

parameters, which complicates model

parameterization and calibration. It predicts the

impact of land management practices on water,

sediment and agricultural chemical yields in

large complex watersheds with varying soils,

land use and management conditions over long

periods of time.

SWAT- Hydrological Modeling

Spatial Scaling of Models Lumped Parameters assigned to

each subbasin

A1 A2

A3

Fully-Distributed Parameters assigned to

each grid cell

Semi-Distributed Parameters assigned to

each grid cell, but cells

with same parameters are

grouped

Digital Elevation Model (DEM)

Digital file that stores the elevation of the land

surface a specified grid cell size (e.g., 90 meters)

Geographic Data FAO Database

Crop Pattern Analysis: The HRUs in SWAT are split into

further into different crops based on the distribution of crops

in each agricultural land

Mostly Rain-fed

Mostly Irrigated

Soil type/ classification

FAO Database: It is suitable for basin wide watersheds

Geographic Data

Hydrologic Data

Meteorological Data

– Temperature

– Precipitation

– Wind speed

– Humidity

Extrapolation of point

measurements

– Theissen Polygons

– Inverse distance weighting

Hydrologic Data

Hydrologic Data

– Streamflow

Peak discharge

Monthy flow volume

Annual flow volume

– Soil moisture

– Groundwater level

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One of the most important basins

in Iran in terms of Surface and

groundwater resources,

agriculture potential, hydropower

generation,…

16000 MCM of potential storage

capacity 40% percent of which

has been constructed

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Karkheh River Basin

Area: 5100000 Hectar

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Karkheh River Basin

Tangmashoureh Garsha

Seymareh

Koranbuzan Sazbon

ROR Karkeh

Karkheh

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Location of

Dams in

Karkheh

Basin

SWAT-CUP

SWAT-CUP is a calibration/uncertainty or

sensitivity program interface for

SWAT. SWAT‐CUP is a public domain

program, and as such may be used and

copied freely. The program links SUFI2,

PSO, GLUE, ParaSol, and MCMC

procedures to SWAT. It enables sensitivity

analysis, calibration, validation, and

uncertainty analysis of SWAT models.

SWAT-CUP SUFI2 ALGORITHM PARALLELIZATION

SWAT-CUP is an application for calibration of SWAT models.

Calibration of SWAT models requires running SWAT simulations hundreds of times with different parameters set

The idea here is to run them separately or in small independent groups and resolve the best parameter configuration that gives simulation effects most corresponding to reality

We have “ready to go” example script set, to run swat sufi2 calibration efficiently from command line

Parameter

s

New SWAT

Inputs

SWAT

Outputs

swEdit.exe

swExtract.ex

e

swat

Output

SUFI-2

MCMC

ParaSol

GLUE

GRID

SWAT-CUP algorithms

Calibration (1985-2000)

br2: 0.46

P-factor: 84%

R-factor: 1.08

Validation (2000-2004)

br2: 0.23

P-factor: 70%

R-factor: 1.72

Aran Station 8 Hydrometric Stations used

Sample Results of the Model Calibration Using SUFI

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Watershed area: 2781 km2

P-factor: 0.84

R-factor: 1.08

Watershed area: 2781 km2

P-factor: 0.7

R-factor: 1.72

Calibration

Validation

Karkheh river basin has been suffering from

drought since 1999and as can be seen it has

affected the validation period of time

Sensitive Parameters Management

– Curve number

Ground water

– Threshold depth of water in the shallow aquifer required

for return flow to occur

– Ground water “ revap “ coefficient

– Initial depth of water in shallow aquifer

– Ground water delay time

Soil parameters

– Hydraulic conductivity

– Available water capacity of the soil layer

– Moist bulk density

Use of Models and Goals ahead

Assessment

– What happens if land use/land cover is

changed?

Prediction

– Flood forecasting

– Crop pattern analysis

Design

– Climate change impacts on river basin

QUESTIONS