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

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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

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Lake Créteil, France

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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

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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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Current velocity and

water temperature at point C

+

-

-

+

17 h

17 h

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

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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

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Simulation results:

water temperature P

C

R

17 h

17 h

12

P

C

R

Simulation results: north-south

current velocity at point C

17 h

17 h

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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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Thank you for your attention

And thanks to:

TUDelft and Deltares (F. van de Ven and R. Uittenbogaard)

Projet Blue Green Dream (I. Tchiguirinskaia, funding)

Région Ile-de-France (funding)