SMIDDEST Advantages of high frequency measurements of the water quality to the understanding of climatic impact in estuarine environment. Etcheber H., Castaing P., Chabaud G., Maneux E., Sautour B., Schmeltz M., Schmidt S., Sottolichio A. UMR 5805 EPOC (Environnements et Paleo-environnements Océaniques) CNRS/University Bordeaux1

Maximum Turbidity Zone (MTZ) « Bouchon vaseux » 4-5 Mt SPM ( > 1 g.L -1 in surface) Salinity Gradient The GIRONDE Estuary Lower Estuary Central Estuary « fluvial » Estuary Isle Garonne Dordogne Pessac La Réole Guîtres « salinity 0 »

SMIDDEST SOMLIT network (Service dObservation en Milieu Littoral) Monthly data over 30 years. Biological, physical and geochemical data.

SMIDDEST Topical questions: - What are the daily and seasonal cycles of the suspended particulate matter and dissolved oxygen contents? - Is the Maximum Turbidity Zone moving upstream and getting larger? - Is there a gradual annual deacrease of oxygen water contents around Bordeaux?

- Temperature - Salinity - Suspended matter content - Dissolved oxygen content - Measurements every 10 minutes (year: 2005) SMIDDEST

Réservoir : de solution chlorée contre dépôts de biofilm. Chambre de mesure : sondes sur un circuit deau en continu Transmetteurs Armoire électrique SEMC : Système Electronique de Mesure et de Contrôle SMIDDEST

Example of recorded data

SMIDDEST Evolution of salinity (A), temperature (B), turbidity (C) and O 2 saturation rate (D) as a function of the tide. A B C D

SMIDDEST Temperature increase

F K E F E K PK 13,5 Salinity increases in the central estuary from one year to the other

SMIDDEST Evolution of salinity (A), temperature (B), turbidity (C) and O 2 saturation rate (D) as a function of the tide. A B C D

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Pleine Mer Basse Mer Pleine Mer

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Pleine mer Basse mer

SMIDDEST Daily cycle of O 2 saturation rate in the Maximum Turbidity Zone during the summer drought in Bordeaux.

SMIDDEST Major factors influencing the decrease of oxygen content in water during summer-time: - High water temperature - Organic load of water - Limited oscillations of waters due to the decrease of summer river discharge and the increase of marine intrusion.

SMIDDEST Oxygen saturation rate of the Garonne waters in Bordeaux during 2006 and 2007 Summers.

SMIDDEST Oxygen saturation rate of the Garonne waters in Bordeaux during 2006 summer. Dramatic consequences for alosa alevins.

SMIDDEST Future evolution of Major Factors: - Increase of water Temperature - Increase of salinity - Decrease of summer river discharge inducing stagnancy (or low oscillations) of waters ( better use of fluvial water ) - Increase of the number of inhabitants inducing more water waste (better management of water waste treatment and inputs

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Future evolution : ETMOM MODEL (Estuarine Turbidity Maximum Oxygen Model) Bordeaux station

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... car pour la terre, le soleil, les vents, ils ne sont point sujets à être emprisonnés, ni détournés, ni dérobés, tandis que cela peut arriver à l'eau, qui, pour de raison, a besoin que la loi vienne à son secours... L'eau est la seule chose la plus nécessaire à l'entretien de la vie, mais il est aisé de la corrompre « Les lois » Platon – IVe siècle avant Jésus- Christ « Eau, tu nas ni couleur, ni arôme, on ne peut pas te définir, on te goûte sans te connaître. Tu nes pas nécessaire à la vie, tu es la vie. » St Exupéry