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Karst Sub-Marine Springs (KSMS)

Karst Sub-Marine Springs (KSMS). Michel BAKALOWICZ HydroSciences, CNRS Partner #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?.

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Karst Sub-Marine Springs (KSMS)

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  1. Karst Sub-Marine Springs (KSMS) Michel BAKALOWICZ HydroSciences, CNRS Partner #2 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? MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  3. Why do KSMS exist? • Because the sea level was below the present sea level: • During Quaternary, for the global ocean, at -100 to -150 m during glaciations • During the Messinian salinity crisis (-5.5 Ma), only in the Mediterranean basin, at -1000 to -1500 m MEDITATE 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 MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  5. The karst conduit network in agreement with its base level… MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  6. … and after the rising up of sea level fresh water sea water MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ Sea level rising up

  7. KSMS in France … MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  8. … and around the Mediterranean Mediterranean coastal karsts MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  9. The Vise KSMS, in the Thau lagoon near Montpellier, at -29 m… Fresh water plume f 1000 mm pipe, « the bell » MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  10. … at the sea surface MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

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

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

  14. From a boat • 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 MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  15. Mapping the freshwater plume in Thau lagoon Sampling network around the spring Isotemperatures ata 3 m depth Bathymetry around the Vise KSMS MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

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

  17. Problems (2) • 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 • Sampling everytime mixed with seawater MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  18. How do we use the data? • 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 • Then comparison of the simulated vs observed plume MEDITATE 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 MEDITATE 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 MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

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

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

  23. Example from the Vise KSMS The water level (water head) Temperature and salinity MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  24. How can we collect fresh water from KSMS? The Géocéan Nymphéa Water « bell » Experiment by Géocéan in 1998 at the Mortola KSMS, between Menton and Vintimille, at the origin of Nymphéa Water MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  25. The Mortola KSMS before taping MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  26. The Mortola KSMS recharge area MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

  27. The Nymphéa Water final project - 27m level - 39m level MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

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

  29. The base surrounding the Mortola KSMS MEDITATE 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 • Best chances close to karst springs • 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 MEDITATE Kick off meeting, Montpellier, Michel BAKALOWICZ

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