Karst Sub-Marine Springs (KSMS)

7 & 8 May 20047 & 8 May 2004 MEDITATE Kick off meeting, Montpellier, MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ Michel BAKALOWICZ

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Karst Sub-Marine Karst Sub-Marine Springs (KSMS)Springs (KSMS)

Michel BAKALOWICZMichel BAKALOWICZ

HydroSciences, CNRSHydroSciences, CNRS

Partner #2Partner #2


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Karst Sub-Marine Springs Karst Sub-Marine Springs (KSMS)(KSMS)

Why do KSMS exist?Why do KSMS exist?

Where are KSMS located?Where are KSMS located?

Why should we take an interest in KSMS?Why should we take an interest in KSMS?

How can we display KSMS?How can we display KSMS?

How can we study KSMS?How can we study KSMS?

How can we collect fresh water from How can we collect fresh water from

KSMS?KSMS?


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Because the sea level was below the Because the sea level was below the

present sea level:present sea level:– During Quaternary, for the global ocean, During Quaternary, for the global ocean,

at -100 to -150 m during glaciationsat -100 to -150 m during glaciations

– During the Messinian salinity crisis (-5.5 During the Messinian salinity crisis (-5.5

Ma), only in the Mediterranean basin, at -Ma), only in the Mediterranean basin, at -

1000 to -1500 m1000 to -1500 m


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Low sea levels give to Low sea levels give to

groundwater flows low base groundwater flows low base

levels, allowing to karst levels, allowing to karst

processes developing conduits processes developing conduits

at depth in carbonate aquifersat depth in carbonate aquifers


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The karst conduit network in The karst conduit network in agreement with its base agreement with its base level…level…


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… … and after the rising and after the rising up of sea levelup of sea level

Sea level rising upSea level rising up


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KSMS in France …KSMS in France …


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Mediterranean coastal karstsMediterranean coastal karsts

… … and around the and around the MediterraneanMediterranean


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The Vise KSMS, in the Thau The Vise KSMS, in the Thau lagoon near Montpellier, at -29 lagoon near Montpellier, at -29

m…m…

1000 mm pipe, « the bell »1000 mm pipe, « the bell »

Fresh water plumeFresh water plume


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… at the sea surface


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Why should we take an Why should we take an interest in KSMS?interest in KSMS?

Groundwater leakage directly into the seaGroundwater leakage directly into the sea

Necessary assessment :Necessary assessment :

– In hydrological balances In hydrological balances

– For controlling the impacts of pumping in For controlling the impacts of pumping in

coastal aquiferscoastal aquifers

Potential groundwater resource in regions Potential groundwater resource in regions

with poor water resourcewith poor water resource


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How can we display How can we display KSMS?KSMS?

By local investigationsBy local investigations

By means of remote sensingBy means of remote sensing

By direct explorationBy direct exploration– made by divers : difficult and not really made by divers : difficult and not really

reliablereliable

– from a boat : requiring important from a boat : requiring important

measures and a long timemeasures and a long time


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Reliability of field Reliability of field investigationsinvestigations– Good knowledge about KSMS existence Good knowledge about KSMS existence

and locationand location

– Results not easy to interpret from remote Results not easy to interpret from remote sensing (2D picture of the sea surface)sensing (2D picture of the sea surface)

– Lowly reliable information from divers Lowly reliable information from divers about flow rates and fresh water quality about flow rates and fresh water quality (overestimation, mixing)(overestimation, mixing)

NO POSSIBLE QUANTIFICATION OF KSMS!


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From a boatFrom a boat

Mapping the fresh water plume Mapping the fresh water plume

from temperature and salinity from temperature and salinity

measurements and from samplesmeasurements and from samples

Necessary means : a boat + 1 or 2 Necessary means : a boat + 1 or 2

marins + 2 to 4 scientists with a marins + 2 to 4 scientists with a

multiparameter probe and multiparameter probe and

sampling bottlessampling bottles


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Sampling networkSampling networkaround the springaround the spring

Mapping the freshwater Mapping the freshwater plume in Thau lagoonplume in Thau lagoon

Bathymetry around the Vise KSMS

Isotemperatures ata 3 m depth


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Problems (1)Problems (1)

Using a boat:Using a boat:– 3 working days… 3 working days…

after several months waiting for good after several months waiting for good conditionsconditions

the boat and men, nice weather, no the boat and men, nice weather, no wind…wind…

– only 2 experiments within 3 years!only 2 experiments within 3 years!– sampling step between 25 and 250 sampling step between 25 and 250

mm


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Problems (2)Problems (2)

With divers:With divers:

– Difficult to work at -30/-40 m depth, Difficult to work at -30/-40 m depth,

time consuming and expansivetime consuming and expansive

– Low reliability of observations : Low reliability of observations : Frequent overestimations of flow rates, Frequent overestimations of flow rates,

based on observed flow velocitiesbased on observed flow velocities Sampling everytime mixed with seawaterSampling everytime mixed with seawater


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How do we use the How do we use the data?data?

Building the freshwater plume in 3D Building the freshwater plume in 3D from :from :– the temperature fieldthe temperature field– the salinity fieldthe salinity field– the flow velocity fieldthe flow velocity field

Knowing the bathymetry and spring Knowing the bathymetry and spring depth, modelling of the plume for depth, modelling of the plume for different flow ratesdifferent flow rates

Then comparison of the simulated vs Then comparison of the simulated vs observed plume observed plume


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Proposed approach :• from the bathymetry, a model simulates the velocity, temperature and salinity fields for several flow rates (from 50 to 1000 L/s).

Comparison simulated vs observed plume : QKSMS < 100 L/sEvaluations by divers and direct flow measurement : about 1000 L/s


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Therefore we had got the Therefore we had got the

idea of developing an idea of developing an

autonomous engine for autonomous engine for

exploring a KSMS exploring a KSMS

freshwater plume rapidly freshwater plume rapidly

for repeating the data for repeating the data

acquisitionacquisition


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Which tasks Which tasks prescribed to the prescribed to the engine?engine? Control and recording the trajectoryControl and recording the trajectory

Measure of temperature and salinityMeasure of temperature and salinity

Measure of the velocity fieldMeasure of the velocity field

Pictures of the plumePictures of the plume


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How can we study KSMS?How can we study KSMS?

The Vise spring station on Thau lagoonThe Vise spring station on Thau lagoon

Measure well of the KSMSMeasure well of the KSMS(P, T, (P, T, 222222Rn, samplings)Rn, samplings)

Measure well of the lagoonMeasure well of the lagoon

To the data loggerTo the data logger

200 m long pipe200 m long pipeFrom the KSMSFrom the KSMS


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Example Example

from the from the

Vise Vise

KSMSKSMS

0

20

40

60

80

100

120

140

01/03/98 01/09/98 01/03/99 01/09/99 01/03/00 01/09/00

Hau

teu

r p

luie

(m

m)

0

20

40

60

80

100

Hau

teu

r (c

m, N

GF

)

Pluie Sète

Charge Vise

Charge Vise (corrigée effet densité)

0

5

10

15

20

25

30

01/03/98 07/09/98 16/03/99 22/09/99 30/03/00 06/10/00

Tem

pér

atu

re (

°C)

0

10000

20000

30000

40000

50000

60000

Con

du

ctiv

ité

(µS

/cm

)

Température Conductivité

The water level (water head)

Temperature and salinity


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The Géocéan The Géocéan

Nymphéa Nymphéa

Water « bell »Water « bell »

Experiment by Géocéan in 1998 at

the Mortola KSMS, between

Menton and Vintimille, at the

origin of Nymphéa Water

How can we collect fresh How can we collect fresh water from KSMSwater from KSMS??


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The Mortola KSMS The Mortola KSMS before tapingbefore taping


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The Mortola KSMS The Mortola KSMS recharge arearecharge area


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The Nymphéa Water final The Nymphéa Water final projectproject

- 27m level

- 39m level


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Electromagnetic flowmeterElectromagnetic flowmeterand C-T-D probesand C-T-D probes

The « tulip », for regulating the flow The « tulip », for regulating the flow

Ascending pipeAscending pipe

BaseBase


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The base surrounding The base surrounding the Mortola KSMSthe Mortola KSMS


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Why should we prefer Why should we prefer control and tapping of control and tapping of

KSMS to on-shore wells?KSMS to on-shore wells? Hazardous results of boreholes in karstHazardous results of boreholes in karst

Best chances close to karst springsBest chances close to karst springs

Necessary control of springs for Necessary control of springs for

surveying man and/or climate impactssurveying man and/or climate impacts

Quantifying flow at the outlets is Quantifying flow at the outlets is

necessary to the sustainable necessary to the sustainable

management of water resourcesmanagement of water resources

Karst Sub-Marine Springs (KSMS)

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