Magest addresses the recommendation of the Committee of Aquatic Natural Environments (1998) of the Adour-Garonne basin to establish a programme for the observation and monitoring of the estuarine Garonne-Dordogne-Gironde system in order to assess the impacts of high turbidity and deoxygenation on water quality and dynamics of biological populations. At the investigation of the Adour Garonne Water Agency, a consortium of water managers and the EPOC laboratory had permitted to implement in 2004-05 the first 4 stations of in situ measurement of the physico-chemical water quality. The Magest network has expanded to 7 measuring stations, distributed over 150 km from the mouth of the Gironde to the lower reaches of the tidal Garonne, Dordogne and Isle Rivers.
The first objective of Magest is to document the databases that enable the description at high temporal resolution of :
- hydrodynamic and sedimentary processes (turbidity, turbidity maximum zone);
- physico-chemical conditions (temperature, salinity, dissolved oxygen) which influence the oxidation of organic matter, the rate of oxygenation, and the dissolution of metals, as Cadmium;
- environmental conditions that control the dynamics of biological populations (survival, growth and migration) in the Gironde estuary.
Magest also is useful to monitor critical episodes (floods, storms, heat waves, summer deoxygenation, …), chronic pollution (urban discharges) or the regional impact of climate change (marine intrusion, occurrence and concentration of turbidity maximum zone, river discharge changes, temperature rise). This high-frequency, multi-site, pluri-annual record contributes to estimate the regional impact of climate change on the water quality of the Gironde estuary.
Lastly, thanks to all the acquired information, Magest must be for the water managers a tool for defining and controlling management policies of the Gironde estuary and of its watershed. Since 2013, the data acquired in Bordeaux and Libourne enable to check and to analyze the objectives of the local Water Planning and Management Scheme in terms of dissolved oxygen concentration.
The coastal MAGEST sites are including in the SNO DYNALIT.
- Coordination : Sabine SCHMIDT (UMR5805 EPOC) ; COTECH MAGEST
- Contact Local : sabine.schmidt [at] u-bordeaux.fr; MAGEST.Gironde [at] gmail.com
The Magest network measures, every 10 to 20 minutes depending on the stations, the temperature, salinity, turbidity and oxygenation in surface estuarine waters. Initially data acquisition was based on MAREL automated systems equipped with endress Hauser sensors. In 2004-2005, the sites of Pauillac, Libourne, Portes and Bordeaux were instrumented. In 2012 the site of Portets was moved to an pstream site (CADILLAC). From 2016, newly developed multi-parameter probes adapted to the high turbidity and easier to operate (Sambat, NKE Instrument) made possible the renewal of the existing stations and the implementation of additional sites (the Verdon, brane, Saint-Denis de Pile).