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1
Modeling internal waves with
Delft3D-FLOW in a shallow urban lake:
Lake Créteil, France
Frédéric Soulignac1*, B. J. Lemaire1,2, R. S. Martins1,3,
I. Tchiguirinskaia1, B. Tassin1 and B. Vinçon-Leite1
1: Laboratoire Eau Environnement Systèmes Urbains (LEESU), Ecole des Ponts ParisTech (ENPC), Champs-sur-Marne, France
2: AgroParisTech, Paris, France
3: Université de Sao Paulo, Brésil
*Corresponding author, e-mail: frederic.soulignac@leesu.enpc.fr
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Context
• 980 lakes in the Ile-de-France region (small dots) and 248 larger than 5 ha (circles)
• Ecosystem services – Drinking water
– Leisure
– Irrigation
– Storm water retention
– Biodiversity conservation
– Local climate regulation
• Urban lakes management – A necessity!
– Improvement by considering their ecological functioning (Birch, 1999)
– Usefulness of numerical models
Water bodies in the Ile-de-France region
from Catherine et al., 2013
Hypothesis: Modeling accurately ecological processes
requires modeling accurately physical processes
3
Objectives
• Wind-forced basin-scale internal waves – Ecological consequences
• Horizontal and vertical fluxes during stratification (Hodges et al., 2000)
• Light availability (Cuypers et al., 2011)
– Observed and simulated in large and deep lakes (Rueda et al, 2003)
– Observed in small and shallow lakes (Pannard et al., 2011)
– Not yet been simulated in small and shallow lakes…
• Objectives – To observe basin-scale internal wave in a shallow lake
– To calibrate and verify the 3D hydrodynamic model Delft3D-FLOW
– To evaluate its capability to reproduce observations
• Foreseen application – To couple Delft3D-FLOW with the biological model DELWAQ-BLOOM
in order to reproduce phytoplankton dynamics
– To use the model configuration coupled with weather forecast in a warning system
5
Lake Créteil- Instrumentation
• Services – Storage of storm water
– Leisure (fishing, bathing, sailing)
– Biodiversity
– Heat wave regulation
• Geometry – Surface area: 40 ha
– Length: 1.5 km
– Width: 300-400 m
– Mean depth: 4.5 m (max: 5.5 m)
• High frequency monitoring since 2012 – Transmitting buoy at point C (30 s)
• Metrological station
• Chain of sensors
– Current profiler at point C (3 min)
– Chains of sensors at point P and R (30 s)
-0.5 m
-1.5 m
-2.5 m
P Stormwater inlet
Outlet
-0.5 m
-1.5 m
-2.5 m
R
2 m
-0.5 m
-1.5 m
-2.5 m
-3.5 m
-4.5 m
C
Current profiler
Meteorological station
Water temperature
Current profiler
Meteorological station
Water temperature
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Characterization of basin-scale
internal waves period • Merian formula (mode V1H1)
• Power spectral density analysis
2
1221
2122 4
gHH
HHLT H1 ρ1
H2 ρ2
L g
tNFFT
XFFTPSD
2
t f
PS
D
X
7
Water temperature and
wind speed at point C
T = 17 h
H1 = 2.5 m ρ1 = 1002.995 kg/m3
H2 = 2.5 m ρ2 = 1003.182 kg/m3
L = 1500 m
g = 9.81 m/s2
T = 17.4 h
Wind amplified internal wave activity
P
C
R
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Difference of water temperature
between points P and R
• Observations results
– Amplification of wave by wind
– Isotherms: wave amplitude = ±0.5 m
– Horizontal differences of water temperature: ±1 °C
17 h
P
C
R
10
Delft3D-FLOW
• Domain – 1148 Cartesian grids: 20m x 20m
– Vertical coordinate system Z-model: 50 cm
– Measured bathymetry
• Heat flux model – Varying cloud cover
– Light extinction
• Turbulence closure model: k-ε
• Bottom shear stress: Manning
• Initial condition and forcing: measurements
• Computational time step: 30 s
• Calibrated in 2012: water temperature and current velocity
• Verified in 2013 and 2014
13
Conclusion
• Conclusions
– Confirmation of the presence of wind-forced basin-scale internal waves
in Lake Creteil
– Delft3D-FLOW reproduced accurately wind-forced basin-scale internal
wave amplitude and frequency
• Foreseen application
– To couple Delft3D-FLOW with the biological model DELWAQ-BLOOM
in order to reproduce phytoplankton dynamics
– To use the model configuration coupled with weather forecast in a
warning system
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