1: The French National Institute for Agricultural Research

Application of Delft3D to evaluate the spatio-

temporal variability of Lake Geneva

ecological status

Delft3D User Meeting - 03 November 2016

Frédéric Soulignac1, P.-A. Danis2,10, D. Bouffard3,

V. Chanudet4, E. Dambrine5, Y. Guenand6, B. Guillermin1,

T. Harmel7,10,2, B. Ibelings8, I. Kiefer3, D. Trevisan1,

R. Uittenbogaard9 and O. Anneville1

3 4 5 6 7 8 9 10

2: The French National Agency for Water and Aquatic

Environments

Lake Geneva

Image from CIPEL, 2016

Lake catchment (7 419 km2)

Catchment of the Rhône river

after Lake Geneva

Rivers

Border France-Switzerland

Lake Geneva

2 Frédéric Soulignac, Delft3D User Days

2016

Surface area = 580 km2

Max depth = 309 m

Residence time = 11 years

Introduction – Material and methods – Results and discussion – Conclusions

I work here!

• European Water Framework Directive (EU, 2000)

• 3 types of indicators: biological, physico-chemical and hydro-morphological

• In France (French technical guide for evaluating ecological status of lakes

and reservoirs, 2016 ; De Bortoli and Argillier, 2008)

– Annual evaluation based on 4 samples taken over the year and at 1 sampling

station

– Parameters

• Chlorophyll a concentration (Chla)

• Ammonium concentration (NH4)

• Nitrate concentration (NO3)

• Total phosphorus concentration (TP)

• Secchi depth (Secchi)

• And others

• Lake Geneva

Evaluation of Lake ecological status

Frédéric Soulignac, Delft3D User Days

2016 3

Image from CIPEL, 2016

Monitoring station SHL2

Introduction – Material and methods – Results and discussion – Conclusions

Satellite observations

• Chla heterogeneities in Lake Geneva (Kiefer et al, 2015)

Frédéric Soulignac, Delft3D User Days

2016 4

Do spatio-temporal heterogeneities bias our estimation of lake ecological

status?

More generally, do these heterogeneities induce uncertainties in our

classification of lakes by ecological quality?

Introduction – Material and methods – Results and discussion – Conclusions

Objectives

• To simulate 5 parameters used for the estimation of lake ecological status

(Chla, NH4, NO3, TP and Secchi)

• To evaluate the variability of Lake Geneva ecological status linked to the

choice of the 4 sample dates

• To evaluate the spatial variability of Lake Geneva ecological status caused

by spatial heterogeneities

• To locate the most representative sampling station of Lake Geneva

5 Frédéric Soulignac, Delft3D User Days

2016

Introduction – Material and methods – Results and discussion – Conclusions

Numerical domain

Frédéric Soulignac, Delft3D User Days

2016 6

820 curvilinear grids (resolution 1 km2)

100 vertical Z-layers (resolution from 1 to 7 m)

Introduction – Material and methods – Results and discussion – Conclusions

Delft3D-FLOW model

Frédéric Soulignac, Delft3D User Days

2016 7

A

B

C D

A

B

C

D

Introduction – Material and methods – Results and discussion – Conclusions

Wind episode

Mixing regime explains Chla heterogeneity (Soulignac et al., 2016)

Delft3D-ECO processes configuration

• Reminder of the 1st objective: to simulate Chla, NH4, NO3, TP and Secchi

• Primary producers: BLOOM (Los, 2009) – Chla derived from 4 phytoplankton groups: diatoms, flagellates, green and blue green algae

• Dissolved inorganic matter – 4 nutrients: NH4, NO3, PO4 and SiO2

– Opal and AAP

• Organic matter – 4 fraction of particulate organic matter (POC1-4, PON1-4 and POP1-4)

– Dissolved organic carbon, nitrogen and phosphorus (DOC, DON and DOP)

• TP: dissolved and particulate phosphorus (including algae)

• Secchi: phytoplankton, particulate organic and inorganic matter

• Primary consumers

Frédéric Soulignac, Delft3D User Days

2016 8

Introduction – Material and methods – Results and discussion – Conclusions

Simulation realization

• 4 years (2009-2012), 1 simulation per year

• Initial condition (horizontally homogenous) – Measurements at monitoring station SHL2

– NH4, NO3, PO4, SiO2, POC, PON, POP

• Hydrodynamic forcing (from Delft3D-FLOW model) – Water velocity

– Water temperature

– Vertical dispersion

• Ecological forcing – Meteorology

• Daily solar radiation

• Constant wind speed (reaeration)

– Tributaries: Weekly flow rates and composition (measurements)

– Zooplankton

Frédéric Soulignac, Delft3D User Days

2016 9

+

Monitoring station SHL2

Introduction – Material and methods – Results and discussion – Conclusions

• Sampling protocol for biological and physico-chemical parameters

(French technical guide for evaluating ecological status of lakes and

reservoirs, 2016 ; De Bortoli and Argillier, 2008) – 4 integrated samples in the euphotic zone

– At 1 monitoring station, the deepest point of the lake

– Observations over the growing season, one per temporal window (TW1-4)

• Annual metrics – Chla: mean value of TW2-4

– NH4 and NO3: maximum value of TW1-4

– TP and Secchi: median value of TW1-4

Calculation of lake ecological status in France

Frédéric Soulignac, Delft3D User Days

2016 10

Introduction – Material and methods – Results and discussion – Conclusions

Calculation of Lake Geneva ecological status

from Delft3D

Parameters Ecological status

Frédéric Soulignac, Delft3D User Days

2016 11

Introduction – Material and methods – Results and discussion – Conclusions

Localisation of the most representative

monitoring station

Ecological status Representativeness

Frédéric Soulignac, Delft3D User Days

2016 12

Introduction – Material and methods – Results and discussion – Conclusions

Ecological model performances

Frédéric Soulignac, Delft3D User Days

2016 13

Monitoring station SHL2

Depth Average 0-30 m

+

Introduction – Material and methods – Results and discussion – Conclusions

Variability of Lake Geneva ecological

status linked to sample dates

Frédéric Soulignac, Delft3D User Days

2016 14

+

Monitoring station SHL2

Year 2010

Chla NH4 NO3 TP Secchi

Bad 0 % 0 % 0 % 0 % 0 %

Poor 98 % 0 % 0 % 0 % 0 %

Medium 2 % 0 % 0 % 4 % 0 %

Good 0 % 0 % 100 % 89 % 51 %

Very good 0 % 100 % 0 % 7 % 49 %

Introduction – Material and methods – Results and discussion – Conclusions

Spatial variability of Lake Geneva ecological

status

15 Frédéric Soulignac, Delft3D User Days

2016

Year 2010

Introduction – Material and methods – Results and discussion – Conclusions

Most representative monitoring station (1/2)

16 Frédéric Soulignac, Delft3D User Days

2016

Year 2010

Introduction – Material and methods – Results and discussion – Conclusions

Most representative monitoring station (1/2)

17 Frédéric Soulignac, Delft3D User Days

2016

Year 2010

Most representative sampling station

Monitoring station SHL2

Introduction – Material and methods – Results and discussion – Conclusions

Conclusions

• A method is proposed to quantify the variability of lake ecological status and

locate the most representative sampling station by using Delft3D in

agreement with WFD

• Seasonal variability of Lake Geneva ecological parameters is well

reproduce by the model

• Spatio-temporal heterogeneities of ecological parameters in Lake Geneva – induce a low variability on ecological status based on Chla

– don’t induce any variability on ecological status based on NH4 and NO3

– induce a higher variability on ecological status based on TP and Secchi

• Heterogeneities can bias our evaluation of lake ecological status but only for

some parameters, for the other parameters the proposed metrics to

evaluate an ecological status are robust and the trophic status estimated is

not influenced by spatio-temporal variability

18 Frédéric Soulignac, Delft3D User Days

2016

Introduction – Material and methods – Results and discussion – Conclusions

1: The French National Institute for Agricultural Research - Inra Lake Hydrobiology Unit, Thonon-les-Bains, France

Thank you!

Delft3D User Meeting - 03 November 2016

Frédéric Soulignac1, P.-A. Danis2,10, D. Bouffard3, V. Chanudet4, E. Dambrine5, Y. Guenand6, B. Guillermin1,

T. Harmel7,10,2, B. Ibelings8, I. Kiefer3, D. Trevisan1, R. Uittenbogaard9 and O. Anneville1

3 4 5 6 7 8 9 10

2: The French National Agency for Water and Aquatic Environments