annual freeze/thaw temperature cycles in soils on the canadian … · 2009. 8. 17. · brett m....

Annual Freeze/Thaw Temperature Cycles in Soils on

the Canadian Boreal Plain

Comparison of SWAT Predictions to Measured Data

Josiane A. Bélanger, Lakehead University

Gordon Putz, University of Saskatchewan

Brett M. Watson, University of Saskatchewan

Ellie E. Prepas, Lakehead University & University of Alberta

Forest Watershed and Riparian Disturbance (FORWARD) Project Collaborative effort by:

Researchers Forest-related industries First Nations Canadian public sectors

FORWARD objectives are to adapt hydrological and water quality modelsto predict the effects of watershed disturbance, for application in forest management planning.

Objectives

Test the SWAT soil temperature (ST) submodel for fine-grained soils in the cold region of the Boreal Plain.

If required, modify the SWAT ST submodel.

Study Site

Vegetation

wetland

deciduous

coniferburned

harvested

Vertical Profile

Additional measurements include: Solar radiation Precipitation Vegetation biomass Soil bulk density

0.1 m 0.5 m 1 m

Soil Temperature

Soil Surface

0.1 m 0.5 m 1 m

2 m 0 m

Air Temperature

Soil Moisture

Soil Temperature Submodel Calculates ST at a specific depth from

air temperature on the current dayand ST on the previous day:

( ) ( ) ( ) ( ){ }ssurfssurfAAirnsoilnsoil TTTdfdzTdzT +−⋅⋅−+⋅= − λλ 1,, 1

where λ is a lag factor

Tsoil(z,dn-1) is ST on previous day for a given depth (z)

df is a depth factor

TAAir is the long-term mean annual air temperature

Tssurf is the soil surface temperature

Soil Temperature Submodel (cont’d) Utilizes multiple input parameters from

three categories:

Soil

Vegetation

Climate

Original SWAT versus Observed ST

-10

-5

0

5

10

15

20

25

1-Nov-05 1-May-06 1-Nov-06 1-May-07 1-Nov-07 1-May-08 1-Nov-08

Observed Soil Temp

Original SWAT

Date

Soil

Tem

per

ature

(oC)

Conifer Site at 0.1 m Depth

r2 = 0.83

MAE = 3.0

RMSE = 3.8

4.8oC

13.1oC

Original SWAT versus Observed ST

-10

-5

0

5

10

15

20

25


Observed Soil Temp

Original SWAT

Date

Soil

Tem

per

ature

(oC)


r2 = 0.83

MAE = 3.0

RMSE = 3.8

Possible Reasons for DifferencesSpring and Summer Vegetation Solar radiation

Autumn Vegetation

Winter Snow

Model Testing Sensitivity analysis was conducted by varying the

following parameters: Aboveground vegetation biomass and residue Depth of the soil profile Bulk density Lag coefficient Snow equation coefficients

Original SWAT (default parameter values) and modified SWAT (varied parameter values) ST submodels were run for each site at 0.1, 0.5 and 1.0 m for each treatment type.

Modifications to ST Submodel Snow albedo (default = 0.8) was decreased:

0.66 for burned and harvested sites 0.43 for conifer, deciduous and wetlands sites

Lag coefficient, λ, was increased

-5

0

5

10

15

20


Observed

λ = 0.70

λ = 0.80

λ = 0.96

λ = 0.97

λ = 0.98

Sensitivity Analysis for Lag Coefficient

Date

Soil

Tem

per

ature

(oC)


Original and Modified SWAT versusObserved ST

Date

Soil

Tem

per

ature

(oC)

Burned Site at 0.5 m Depth

Original SWAT

r2 = 0.77

MAE = 3.7

RMSE = 4.1

Modified SWAT

r2 = 0.96

MAE = 1.9

RMSE = 2.4

-5

0

5

10

15

20

1-Aug-06 1-Feb-07 1-Aug-07 1-Feb-08 1-Aug-08

Observed Soil Temp

Original SWAT

Modified SWAT


Date

Soil

Tem

per

ature

(oC)

Wetland Site at 0.5 m Depth

Original SWAT

r2 = 0.66

MAE = 2.3

RMSE = 2.8

Modified SWAT

r2 = 0.96

MAE = 0.7

RMSE = 0.8

-5

0

5

10

15

20

1-Jul-06 1-Jan-07 1-Jul-07 1-Jan-08 1-Jul-08 1-Jan-09

Observed Soil Temp

Original SWAT

Modified SWAT


Date

Soil

Tem

per

ature

(oC)


Original SWAT

r2 = 0.70

MAE = 2.6

RMSE = 3.1

Modified SWAT

r2 = 0.90

MAE = 1.3

RMSE = 1.7

-5

0

5

10

15

20


Observed Soil Temp

Original SWAT

Modified SWAT

Discussion Model efficiency was increased for all

depths and treatments by increasing the lag coefficient

Maximum soil temperature differences in summer and winter were reduced

Snow Insulation Equation Determines the insulation provided by

vegetation or snow:

where bcv is the insulation parameter

CV is the above ground biomass and residue in kg⋅ha-1

SNO is the snow depth in mmH2O

Parameters: A = 6.005

B = 0.3002

( ) ( )

⋅−+⋅⋅−+= − SNOBASNO

SNOCVCV

CVbcvexp

,10297.1563.7exp

max 4

Sensitivity Analysis for Snow EquationParameter A

Date

Soil

Tem

per

ature

(oC)


-5

-4

-3

-2

-1

0

1

2

3

4

5


ObservedA = 0A = 0,1A = 1,0A = 10A = 6,055

Sensitivity Analysis for Snow EquationParameter B

Date

Soil

Tem

per

ature

(oC)


-5

-4

-3

-2

-1

0

1

2

3

4

5


Observed

B = 0

B = 0,01

B = 0,1

B = 1

B = 0,3002

Conclusions The modified SWAT was able to

effectively model ST in the spring, summer and autumn seasons on the Boreal Plain.

Insulation by a deep snowpack is not reflected in the SWAT model.

To simulate ST in winter months for northern climates, further modificationsto the model must account for deep and persistent snowpacks.

Acknowledgements Millar Western Forest

Products Ltd. and the Natural Sciences and Engineering Research Council of Canada (NSERC) for funding this research.

Past and present members of FORWARD: Janice Burke

Nicole Fraser

Steve Nadworny

Dr. Douglas MacDonald

Mark Serediak

Dr. Ivan Whitson

The FORWARD project is funded by: NSERC Collaborative Research and

Development Program Millar Western Forest Products Ltd. Blue Ridge Lumber Inc. (a division of

West Fraser Timber Company Ltd.) Alberta Newsprint Company (ANC

Timber) Vanderwell Contractors (1971) Ltd. Abitibi Bowater Inc. Buchanan Forest Products Ltd. Buchanan Lumber (a division of

Gordon Buchanan Enterprises) Talisman Energy Inc. TriStar Oil & Gas Ltd. Canada Foundation for Innovation Alberta Forestry Research Institute Forest Resource Improvement

Association of Alberta FedNor Ontario Innovation Trust Living Legacy Research Program

annual freeze/thaw temperature cycles in soils on the canadian … · 2009. 8. 17. · brett m....

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