The second largest body of salt water in Europe, the Etang de Berre, or rather the question of its rehabilitation, is an old sea serpent for the inhabitants of western Marseille. For more than thirty years, residents, associations and politicians have been fighting for this coastal lagoon, which communicates with the Mediterranean through the Caronte canal (
dug by the Roman legions and 6.5 kilometers long) which crosses the city of Martigues, finds an ecological balance. Last December, a parliamentary report led to the holding of workshops bringing together the State, local authorities, and the Gipreb mixed union, in order to establish a roadmap. 20 minutes make the point.
What is the problem again?
The ecological imbalance of the Etang de Berre dates back to 1966 and the commissioning of the EDF hydroelectric power station in Saint-Chamas, supplied by a diversion of water from the Durance. This caused a massive and sudden inflow of fresh water, altering its salinity. This power station discharged 2.1 billion cubic meters of fresh water into the pond until 2005, when the discharges were reduced to 1.2 billion cubic meters in 2005 after the lawsuit d ‘associations.
Before that, the supply of fresh water was essentially limited to the waters of two small Provençal rivers which flow into the pond: the Touloubre and the Arc. The total capacity of the Etang de Berre is 980 million cubic meters. The current discharges from this plant therefore correspond to more than once the volume of water in the pond and have caused significant siltation, due to the discharge of silt contained in these waters.
This change in the composition of the water was aggravated by the collapse of the Rove tunnel in 1963. The latter communicated the north of the harbor of Marseille with the Etang de Berre. In addition to bringing salt water and allowing small fishing boats not to venture out to sea, which can be dangerous on mistral days, this tunnel creates a gentle current in the pond. So, what are the solutions put forward in this roadmap which establishes 19 objectives and actions?
Reduction and seasonalization of discharges from the EDF power plant
The first of them is based on a new pattern of water releases from the Saint-Chamas hydroelectric plant. “The agreement with EDF fell”, rejoiced Éric Diard, LR deputy for the constituency of the south-east of the pond who carried the report with two of his colleagues, Jean-Marc Zulesi (LREM) and Pierre Dharreville (PCF). “EDF has agreed to reduce its discharges by 25% and adopt a seasonal plan”, explains the one who believes that “the planets are finally aligned” for the rehabilitation of the pond.
Concretely, the fresh water supply will be established at 900,000 cubic meters per year with more discharge in winter than in summer, a period during which the pond suffers more from external nutrient inputs. “Anything that will allow the pond to receive less fresh water is a good thing. We are on the right track, ”said Raphaël Grisel, director of Gipreb.
Reopening of the Rove tunnel
If it does not reduce the supply of fresh water, the reopening of the Rove tunnel should make it possible to add salt water and “good quality”, adds Raphaël Grisel. This will also make it possible to offer “a refuge area for fish. Because in each crisis, the fish have no other solution than to leave the pond or die ”. As in the fall of 2018, when following exceptional discharges from the EDF power plant, the pond experienced a significant anoxic crisis, i.e. a lack of oxygen.
The cost of restoring this structure, built in the first half of the 20th century, long claimed by associations, should be borne by the Region. In 2018, studies conducted by Gipreb estimated this cost at 30 million euros.
But the situation has since changed, as a new collapse occurred in 2019. ”
Event that looks like a helping hand from fate. “Companies have come to provide reinforcements and have built a new platform which will greatly simplify the program”, continues Raphaël Grisel. However, this reopening is not fully acquired. New studies have been commissioned and, subject to the validation of this program, work should begin in 2024.
What else ?
As has been said, the roadmap has 19 points. Among other things to note, let us note a project to delineate the Cadarache basin. It is from here that part of the waters of the Durance leave to supply the EDF canal, and it is largely silted up. The cleaning would reduce the load of silt that ends its course in the pond. De-waterproofing the watershed to reduce runoff and limit the contribution of pollutant to the pond is also discussed, as is the connection of facilities to the sewerage network. A feasibility study for a partial diversion of water allowing its reuse is also on the agenda. Finally, in the area of economic activities, support for professional mussel culture fishing activities is mentioned.
Is it sufficient ?
Are these solutions likely to save the Etang de Berre? If they are undoubtedly going in the right direction, they do not satisfy René Benedetto, president of the Étang Nouveau association, which has been fighting since 1988 for its rehabilitation. “The measures are timid. We are below the stakes, it would be necessary to limit the discharges from the plant to 300,000 cubic meters, ”he said. “We tinker and arrange a little, but that does not solve the problem of massive supply of fresh water. Water which, moreover, is sorely lacking in the Durance, ”he adds.