7 & 8 May 2004 MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 1 Karst Sub-Marine Springs (KSMS) Michel BAKALOWICZ HydroSciences, CNRS Partner #2

7 & 8 May 2004 MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 2 Karst Sub-Marine Springs (KSMS) Why do KSMS exist? Where are KSMS located? Why should we take an interest in KSMS? How can we display KSMS? How can we study KSMS? How can we collect fresh water from KSMS?

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 3 Why do KSMS exist? Because the sea level was below the present sea level: Because the sea level was below the present sea level: –During Quaternary, for the global ocean, at to -150 m during glaciations –During the Messinian salinity crisis (-5.5 Ma), only in the Mediterranean basin, at to m

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 4 Why do KSMS exist? Low sea levels give to groundwater flows low base levels, allowing to karst processes developing conduits at depth in carbonate aquifers Low sea levels give to groundwater flows low base levels, allowing to karst processes developing conduits at depth in carbonate aquifers

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 5 The karst conduit network in agreement with its base level…

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 6 … and after the rising up of sea level Sea level rising up

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 7 KSMS in France …

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 8 Mediterranean coastal karsts … and around the Mediterranean … and around the Mediterranean

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 9 The Vise KSMS, in the Thau lagoon near Montpellier, at -29 m…  1000 mm pipe, « the bell » Fresh water plume

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 10 … at the sea surface

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 11 Why should we take an interest in KSMS? Groundwater leakage directly into the sea Groundwater leakage directly into the sea Necessary assessment : Necessary assessment : –In hydrological balances –For controlling the impacts of pumping in coastal aquifers Potential groundwater resource in regions with poor water resource Potential groundwater resource in regions with poor water resource

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 12 How can we display KSMS? By local investigations By local investigations By means of remote sensing By means of remote sensing By direct exploration By direct exploration –made by divers : difficult and not really reliable –from a boat : requiring important measures and a long time

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 13 Reliability of field investigations –Good knowledge about KSMS existence and location –Results not easy to interpret from remote sensing (2D picture of the sea surface) –Lowly reliable information from divers about flow rates and fresh water quality (overestimation, mixing)  NO POSSIBLE QUANTIFICATION OF KSMS!

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 14 From a boat Mapping the fresh water plume from temperature and salinity measurements and from samples Mapping the fresh water plume from temperature and salinity measurements and from samples Necessary means : a boat + 1 or 2 marins + 2 to 4 scientists with a multiparameter probe and sampling bottles Necessary means : a boat + 1 or 2 marins + 2 to 4 scientists with a multiparameter probe and sampling bottles

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 15 Sampling network around the spring Mapping the freshwater plume in Thau lagoon Bathymetry around the Vise KSMS Isotemperatures at a 3 m depth

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 16 Problems (1) Using a boat: Using a boat: –3 working days… after several months waiting for good conditions after several months waiting for good conditions the boat and men, nice weather, no wind… the boat and men, nice weather, no wind… –only 2 experiments within 3 years! –sampling step between 25 and 250 m

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 17 Problems (2) With divers: With divers: –Difficult to work at -30/-40 m depth, time consuming and expansive –Low reliability of observations : Frequent overestimations of flow rates, based on observed flow velocities Frequent overestimations of flow rates, based on observed flow velocities Sampling everytime mixed with seawater Sampling everytime mixed with seawater

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 18 How do we use the data? Building the freshwater plume in 3D from : Building the freshwater plume in 3D from : – the temperature field –the salinity field –the flow velocity field Knowing the bathymetry and spring depth, modelling of the plume for different flow rates Knowing the bathymetry and spring depth, modelling of the plume for different flow rates Then comparison of the simulated vs observed plume Then comparison of the simulated vs observed plume

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 19 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/s Evaluations by divers and direct flow measurement : about 1000 L/s

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 20 Therefore we had got the idea of developing an autonomous engine for exploring a KSMS freshwater plume rapidly for repeating the data acquisition

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 21 Which tasks prescribed to the engine? Control and recording the trajectory Control and recording the trajectory Measure of temperature and salinity Measure of temperature and salinity Measure of the velocity field Measure of the velocity field Pictures of the plume Pictures of the plume

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 22 How can we study KSMS? The Vise spring station on Thau lagoon Measure well of the KSMS (P, T, 222 Rn, samplings) Measure well of the lagoon To the data logger 200 m long pipe From the KSMS

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 23 Example from the Vise KSMS The water level (water head) Temperature and salinity

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 24 The Géocéan Nymphéa 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 water from KSMS ?

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 25 The Mortola KSMS before taping

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 26 The Mortola KSMS recharge area

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 27 The Nymphéa Water final project - 27m level - 39m level

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 28 Electromagnetic flowmeter and C-T-D probes The « tulip », for regulating the flow Ascending pipe Base

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 29 The base surrounding the Mortola KSMS

7 & 8 May 2004MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ 30 Why should we prefer control and tapping of KSMS to on-shore wells? Hazardous results of boreholes in karst Hazardous results of boreholes in karst Best chances close to karst springs Best chances close to karst springs Necessary control of springs for surveying man and/or climate impacts Necessary control of springs for surveying man and/or climate impacts Quantifying flow at the outlets is necessary to the sustainable management of water resources Quantifying flow at the outlets is necessary to the sustainable management of water resources