2011 International SWAT Conference Toledo, Spain, June 15-17 2011

Kiesel J.1, Fohrer N.1, Schmalz B.1, Brown G.L.2

Coupling SWAT with In-stream Models for an

Integrated Assessment of Sediment Transport

1 Institute for the Conservation of Natural Resources, Dep. of Hydrology, Kiel University

2 USACE Coastal and Hydraulics Laboratory, ERDC, Vicksburg, MS

Dep. of Hydrology and Water Resources Management – Fohrer et al. -2-

Outline

1. Background and scope of the project

2. Model coupling

3. Modeling water fluxes on three scales

4. Modeling sediment fluxes on three scales

5. Discussion

Dep. of Hydrology and Water Resources Management – Fohrer et al. -3-

Integrated ecohydrological river basin assessment

Kirchweddelbek (SH), Foto: U. Holm

Catchment

processes

In-stream

processes

(1D, 2D)

Habitat

Reality Abstraction

HEC-RAS

Modelling

Dep. of Hydrology and Water Resources Management – Fohrer et al. -4-

The in-stream models

Widely used hydraulic model for simulating open

channel flow and sediment processes in river networks

ArcGIS interface available

Adaptive Hydraulics model for simulating 2D-shallow

water problems with sediment transport on a triangular

finite element mesh

Dynamic adaption of mesh resolution during simulation

ArcGIS interface had to be programmed

HEC-RAS

1D

(USACE 2010)

2D

(Berger et al. 2010)

Dep. of Hydrology and Water Resources Management – Fohrer et al. -5-

Why additional in-stream models?

HEC-RAS

1D

(USACE 2010)

2D

(Berger et al. 2010)

supplies spatially distributed results from the catchment

no differentiation of stream properties beyond subbasin (Arnold et al. 1998)

supplies spatially distributed results at cross sections

too coarse to model in-stream morphodynamics for

habitat assessments

supplies spatially distributed results on points

very high resolution in the stream possible

Dep. of Hydrology and Water Resources Management – Fohrer et al. -6-

Outline

1. Background and scope of the project

2. Model coupling

3. Modeling water fluxes on three scales

4. Modeling sediment fluxes on three scales

5. Discussion

Dep. of Hydrology and Water Resources Management – Fohrer et al. -7-

Lowland characteristics

(JOSE 2006)

Kielstau catchment, UNESCO demosite for Ecohydrology

• 50km²

• 8.2°C

• 870mm/a

• Low hydraulic

gradients,

near-surface

groundwater

• Agricultural

land use

• Urban

influence

Dep. of Hydrology and Water Resources Management – Fohrer et al. -8-

Process depiction on three scales

3 km

Flow,

Sediment Velocity,

Depth,

Sediment

HEC-RAS

Velocity,

Depth,

Sediment

Dep. of Hydrology and Water Resources Management – Fohrer et al. -9-

Model coupling

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

LTOTday

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

06/02 12/02 06/03 12/03 06/04 12/04 06/05 12/05 06/06 12/06 06/07

Dis

ch

arg

e m

³/s

Discharge measured

Discharge modeled(drains+potholes)

Q

ArcGIS 9.2 PYTHON script:

• SWAT tributary flows (output.rch) are transferred to the according

HEC-RAS cross sections. Subbasin flows are distributed

among all subbasin cross sections

• SWAT tributary sediment loads (output.sub) are transferred to

the according HEC-RAS cross sections. Subbasin loads are

distributed among the tributary cross sections

• SWAT water temperature is transferred to HEC-RAS time series

• The interface supplies quasi unsteady and steady flow data

HEC-RAS

Dep. of Hydrology and Water Resources Management – Fohrer et al. -10-

HEC-RAS Model coupling

HEC-RAS

channel

HEC-RAS

cross section

(xs)

ADH

mesh

10m

Dep. of Hydrology and Water Resources Management – Fohrer et al. -11-

HEC-RAS flow values

and loads of each grain

fraction are transferred

from the cross section

to the ADH inflow

mesh nodes for each

daily time step

HEC-RAS

channel

HEC-RAS

cross section

(xs)

ADH

mesh

ADH

inflow

nodes

HEC-RAS Model coupling

Dep. of Hydrology and Water Resources Management – Fohrer et al. -12-

Outline

1. Background and scope of the project

2. Model coupling

3. Modeling water fluxes on three scales

4. Modeling sediment fluxes on three scales

5. Discussion

Dep. of Hydrology and Water Resources Management – Fohrer et al. -13-

Catchment hydrology

0

1

2

3

4

5

1999 2000 2001 2002 2003 2004

0

40

80

120

160

200

240

280

PCP

Observed

Modelled (calibration)

0

1

2

3

4

5

2004 2005 2006 2007 2008 2009

0

40

80

120

160

200

240

280

PCP

Observed

Modelled (verification)

mm

Flo

w [m

³/s]

Flo

w [m

³/s]

r² = 0.82

NS = 0.78

r² = 0.82

NS = 0.78 mm

Sinks Drains

Dep. of Hydrology and Water Resources Management – Fohrer et al. -14-

1D stream hydraulics HEC-RAS

C

A B

Dep. of Hydrology and Water Resources Management – Fohrer et al. -15-

1D stream hydraulics HEC-RAS

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Measured

Mo

de

lle

d

C B A

HEC-RAS depth [m]

0.0

0.2

0.4

0.6

0.8

0.0 0.2 0.4 0.6 0.8

Measured

Mo

de

lle

d

C B A

HEC-RAS velocity [m/s]

Water depth Flow velocity

r²=0.90 r²=0.88

24 flow scenarios: Qmin = 0.06m³/s Qmax = 1.26m³/s

Dep. of Hydrology and Water Resources Management – Fohrer et al. -16-

2D stream hydraulics

20m

depth cross sections

depth and velocity cross sections

Dep. of Hydrology and Water Resources Management – Fohrer et al. -17-

0.0

0.2

0.4

0.6

-0.2 0.0 0.2 0.4 0.6

Measured

Mo

de

lled

2D stream hydraulics

Water depth Flow velocity

r²=0.70 0.0

0.2

0.4

0.6

0.8

1.0

1.2

0.0 0.2 0.4 0.6 0.8 1.0 1.2

Measured

Mo

de

lled

r²=0.93

1 flow scenario: Q = 0.73m³/s

Dep. of Hydrology and Water Resources Management – Fohrer et al. -18-

2D stream hydraulics

20m

depth cross sections

depth and velocity cross sections

1

2

3

Dep. of Hydrology and Water Resources Management – Fohrer et al. -19-

0.0

0.2

0.4

0.6

0.8

1.0

0.5 1.0 1.5 2.0 2.5 3.0 3.5

0.0

0.2

0.4

0.6

0.5 1.0 1.5 2.0 2.5 3.0 3.5

2D hydraulics – cross sections

0.0

0.2

0.4

0.6

0.8

1.0

0.5 1.0 1.5 2.0 2.5 3.0

0.0

0.2

0.4

0.6

0.5 1.0 1.5 2.0 2.5 3.0

modelled measured

Water depth [m] Flow velocity [m/s]

1

2

3

0.0

0.2

0.4

0.6

0.8

1.0

0.5 1.0 1.5 2.0 2.5 3.0 3.5

0.0

0.2

0.4

0.6

0.5 1.0 1.5 2.0 2.5 3.0 3.5

Distance from left bank [m] Distance from left bank [m]

Dep. of Hydrology and Water Resources Management – Fohrer et al. -20-

Outline

1. Background and scope of the project

2. Model coupling

3. Modeling water fluxes on three scales

4. Modeling sediment fluxes on three scales

5. Discussion

Dep. of Hydrology and Water Resources Management – Fohrer et al. -21- 21

Daily sediment loads in lowland catchments

Field River Drains

0

1

2

3

4

5

6

7

8

9

10

11

12

Oct-

06

Nov-0

6

Dec-0

6

Jan-0

7

Feb-0

7

Mar-

07

Apr-

07

May-0

7

Jun-0

7

Jul-07

Aug-0

7

Sep-0

7

Oct-

07

Nov-0

7

Dec-0

7

Jan-0

8

Feb-0

8

Mar-

08

Apr-

08

May-0

8

Jun-0

8

Jul-08

Aug-0

8

Sep-0

8

Oct-

08

Nov-0

8

Dec-0

8

Sedim

ent lo

ad [kg /d] )

Simulated MeasuredSeries3

Calibration Validation

Loading from HRUs/Subbasins

Loading from Subbasins + channel degradation/deposition

15% 15% 70%

R²=0.63

NSE=0.57

R²=0.65

NSE=0.58

Dep. of Hydrology and Water Resources Management – Fohrer et al. -23-

1D stream sediment - temporal HEC-RAS

-5

5

15

25

35

01/2

00

7

04/2

00

7

07/2

00

7

10/2

00

7

01/2

00

8

04/2

00

8

07/2

00

8

10/2

00

8

01/2

00

9

04/2

00

9

07/2

00

9

10/2

00

9

[t/day]

Sed. load MUSLE&DRAIN&BED

Sed. load DRAIN

Sed. load MUSLE

Measured load

Missing measured values

r² = 0.31, monthly r² = 0.68

Dep. of Hydrology and Water Resources Management – Fohrer et al. -24-

1D stream sediment - spatial HEC-RAS

Channel change in 4 years (2006 to 2009)

- 6.6 cm

0 cm

+ 3.0 cm

Dep. of Hydrology and Water Resources Management – Fohrer et al. -25-

2D stream sediment

Bed displacement [m]

-0.13 - -0.08

-0.08 - -0.05

-0.05 - -0.04

-0.04 - -0.02

-0.02 - -0.01

-0.01 - 0.00

0.00 - 0.01

0.01 - 0.02

0.02 - 0.04

0.04 - 0.060 31.5

m

20m

Bed displacement 01.-30. April 2008

Dep. of Hydrology and Water Resources Management – Fohrer et al. -26-

Outline

1. Background and scope of the project

2. Model coupling

3. Modeling water fluxes on three scales

4. Modeling sediment fluxes on three scales

5. Discussion

Dep. of Hydrology and Water Resources Management – Fohrer et al. -27-

Discussion

•The combined SWAT – HEC-RAS model is a feasible way to model different

sediment pathways over yearly periods in a reasonable resolution

•The shown temporal and spatial 1D sediment results are plausible and can be

used to identify erosion and deposition sections

•The combined HEC-RAS – ADH model can simulate detailed substrate

conditions, but with a high computational demand

•The shown spatial 2D sediment results need further calibration, as current

displacement rates are too high

•The capability of the model system to depict hydraulic- and substrate conditions

on different scales based on catchment and in-stream properties is valuable for

habitat assessments

Dep. of Hydrology and Water Resources Management – Fohrer et al. -28- Thank you for your attention

Dipl. Ing. Jens Kiesel