Application of the simulation models THESEUS and HYDRUS

Transcription

Application of the simulation models THESEUS and
HYDRUS-1D at different european forested test
sites
Martin Wegehenkel
Institute of Landscape Systems Analysis
ZALF Müncheberg
Modelling-Workshop Freising 27th-29th April, 2010
• Outline:
• Application of the models THESEUS (Wegehenkel, 2005) and
HYDRUS-1D (Simunek et al., 2008) at 9 forested experimental test
sites
• Test and comparison of both models
• Analysis of simulation precision and data quality
• Presentation of some selected results: Celerina, Solling Spruce and
Solling Beech
Comparison of the actual model set up for Hydrus-1D and THESEUS
Vegetation
Hydrus-1D (Simunek et al. 2008)
Minutes – Years
1 cm layer = 90-280 layers
depending on soil profile depth
Seconds - daily
Time series of net precipitation,
evaporation, transpiration calculated
by THESEUS and LAI from the data
providers
-
Evapotranspiration
-
Interception
Ψ(θ) and K(Ψ)
Soil water fluxes
Van Genuchten (1980)
Richards-Equation using numerical
solution
Inverse modelling
Hydraulic parameters using time
series of measured pressure heads,
soil water contents and fluxes
Yes
Yes
Yes
Yes
Time scale
Profile discretization
Time Step
Met. Data
Heat transport
Dual porosity
Solute transport
Graphical uses interface
THESEUS (Wegehenkel 2005)
Days – Years
10 cm layer = 9 -20 layers
depending on soil profile depth
Minutes-daily
Time series of precipitation,
temperature, global radiation, air
humidity and wind speed
Semiempirical forest model using
external time series of LAI and
rooting depth as driver variables
Penman-Monteith equation based on
algorithms obtained from the model
FOREST_BGC (Running et al. 1991)
Single linear storage using LAI
Van Genuchten (1980)
Simple Richards equation using the
model SAWAH (Ten Berge et al.
1998)
No
No
No
No
No
Transpirationmodel THESEUS
Forest-Model
1. Calculation of potential transpiration Tpot in mm d-1 (RUNNING und COUGHLAN 1988, RUNNING und
GOWER 1991)
rad
c
c
vpd
r
a
p
Tpot
1
r
c
r
a
Tsec LAI
1000
= slope of the function saturation vapour pressure versus air temperature (mbar K-1), radc = Net
radiation (W m-2), cp = specific heat of air at constant pressure (J kg-1 K-1), = air density (kg m-3), vpd
= vapour pressure deficit (mbar), ra = aerodynamic resistance (s m-1) = Psychrometerkonstante, rc =
canopy resistance (s m-1), Tsec = day length (sec), = latent heat (J kg-1), LAI = Leaf area index (m2 m-2)
2. Interception using specific interception capacity of the forest stand IC (mm d-1):
Int
Min
IC
C ic
LAI , IC
radc Tsec
CIC = specific interception coefficient (LAI-1 d-1).
3. Evaporation PE in mm d-1
PE
radc Tsec
Int
Modelling procedures:
•
•
•
•
•
•
•
•
•
No correction of precipitation inputs
The Van Genuchten parameters θs, θr, α and n were estimated by the
program SHYPFIT (Durner 2005) using the provided soil water contents
at pF4.2 (=WP), pF2.0 (=FC) and pF0.0 (=total porosity)
θs, θr, α and n for organic layers obtained from literature
Initial moisture conditions obtained from the corresponding data set
Uncalibrated (= no parameter optimization) application of THESEUS at
the test sites Celerina, Solling Beech and Solling Spruce
Using LAI, rooting depth and phenogical data from the corresponding
data sets
THESEUS provides time series of net precipitation, evaporation,
transpiration, LAI and rooting depth as input and upper boundary
condition for the application of HYDRUS-1D
Inverse modelling of hydraulic parameters with Hydrus-1D using time
series of measured pressure heads at the Solling Spruce test site
Using optimized hydraulic parameter set in the application of Hydrus-1D
and THESEUS at the Solling spruce test site
Comparison of simulated (by THESEUS) and measured daily throughfall,
Solling Spruce
Daily rates of precipitation (Prc in mm d-1), measured and simulated pressure
heads in 10 cm, 20 cm, and 40 cm depth (Prh10-Prh40 in hPa), Solling Spruce
heads in 100 and 180 cm depth (Prh100-Prh180 in hPa), Solling Spruce
Daily rates of precipitation (Prc in mm d-1), measured and simulated soil water
contents in 2 cm depth (Swc2 in Vol%), Solling Spruce
Comparison of simulated and measured soil water contents,
Solling Spruce, 2cm depth
Hydrus-1D
THESEUS
Comparison of simulated (byTHESEUS) and measured daily
throughfall, Celerina (left) and Solling beech (right)
heads in 15 cm, 30 cm, 50 cm and 80 cm depth (Prh15-Prh80 in hPa), Celerina
heads in 10 cm, 20 cm and 40 cm depth (Prh10-Prh40 in hPa), Solling Beech
heads in 100 cm and 180 cm depth (Prh100-Prh180 in hPa), Solling Beech
• Preliminary conclusions:
• Van Genuchten Parameter estimation with only three points – uncertainty in
hydraulic functions.
• Van Genuchten Parameters for organic layers difficult to identify
• THESEUS model had problems with stagnant water and saturated
conditions at the lower soil profile boundary – due to the simple procedure
to solve the RICHARD‘s equation (see results for Solling beech site).
• Inverse modelling procedures depend on the quality of the data used for the
objective function and reliable estimates of the range of the parameters.
• In the actual state, overall simulation quality of both models using e.g. the
comparison of simulated with measured soil water contents is bad (see 2cm
depth at Solling Spruce site).
• Check of model calculations and measured data.
Thank you for your attention !
A special thank to the organizers of the workshop
and the data providers as well !

Application of the simulation models THESEUS and HYDRUS

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