A look over Couesnon Watershed main issues regarding biodiversity and water quality

Couesnon river, located in the North-Western region of France, has been struggling for years with physical degradation and insufficient water quality. The river’s hedges and banks are damaged and the water is loaded with nitrates, pesticides and other nefarious matters. Adding to this, with climate change, there has also been a problem with water quantity, in dry years, and the River is often unable to provide water for all economic activities it serves.

Sylvie Le Roy works for SAGE, an organism that establishes the basic guidelines for the management and preservation of water resources on the Couesnon and an important stakeholder on ALICE’s French case study.

In this interview she describes the main issues of the Couesnon watershed and how ALICE can help link water quality and biodiversity.

Sylvie Le Roy – We are here at the outlet of the Couesnon, the Couesnon river flows at the base of the Mont St Michel. Its watershed covers about 90 municipalities, has 90.000 inhabitants. It is subjected to a planning document that is drawn up by a Local Water Commission, which has tried to define the major issues of water quality protection, environmental protection to comply with the European Water Framework Directive.

The main issues are, on one hand the improvement of the water quality for the physicochemical parameters: nitrates, phosphorus, pesticides, organic matter too, there are many erosive runoff phenomena. On the other hand, in order to reach the good water status according to the European Water Framework Directive, we will have to work a lot, to restore the physical quality of the rivers because we have a lot of rivers that are degraded. So, these are really the two major issues on which the Local Water Commission has focused.

We also have a quantitative issue that is starting to become significant with the advent of climate change and we realize that during dry years in summer we will have trouble meeting all the needs for water of the watershed.

Between the needs for drinking water, industries, agriculture, we are sometimes at the limit of being able to provide water for all the activities, for all the sectors of activities. So, there are also solutions to put in place to be safe. And so, the work to do on the natural areas, on the restoration of natural areas is to make the natural environment more resilient, reconnect waterways with wetlands, again a very important issue to meet this quantitative issue in the years to come.

The Local Water Commission has defined a document that has a legal scope. There are two sorts of measures. There are measures that are going to have a legal scope, particularly that which applies to urban planning documents. All collectivities will have to protect waterways, wetlands, hedged elements in planning documents. Also, there are many provisions, and they are the majority, which are based on volunteering.

So then, we go find farmers, we go find the Watershed Syndicates, who are responsible for the restoration of the aquatic areas, the drinking water syndicates that accompany the stakeholders, the communities to pollute less, to change the practices in farms and in town centers so that they have less pesticides.

And then the groupings of municipalities and the grouping of agglomerations do a big job of restoration of the “bocage” (hedges and banks).

The “bocage” are hedges and embankments, physical barriers that will limit landslides -often loaded with nutrients, pesticides- towards the water.

It’s more important because there are also issues concerning the bay of Mont St Michel.

At this level we work with the other SAGEs (Water management bodies) of the other watersheds of the bay, and here the issues are different because it is about having a water quality to answer the economic stakes of the shellfish farming, shell seeking, but also, a little north in Cancale and Granville, bathing issues.

Moreover, there is a very important biodiversity issue. In particular, salt marshes, which are classified Natura 2000, show a decline in plant biodiversity and an invasion of these salt marshes by the maritime quackgrass. This phenomenon seems to be also due to an enrichment of the environment by the nitrates that come from the different watersheds of the bay.

In addition, we have not talked about it, we also have an issue -to finish perhaps- a challenge of marine submersion that appears with the rise of the sea level.

One could on the area here -which goes from Cancale, east of the Couesnon all along the Couesnon coastline- could also know episodes of marine submersion related to the flood episodes of the watersheds.

It is a process of considering this risk and protection. Then, it will go through the restoration of dikes and process of securing populations and avoid building in the future in areas subject to the risk of submersion.

What would you expect from a project like ALICE?

Sylvie Le Roy – ALICE project immediately interested us because, indeed, we realize that here, water quality, biodiversity, are issues that are strongly linked.

Here, the water quality in the rivers is measured by indicators of biodiversity of the aquatic organisms. All of these challenges will have to be addressed by sustainable land use scenarios.

So, with this project, we hope that indeed scientists will be able to enlighten us on the impact of different scenarios of management that will be discussed by members of the Local Water Commission, but also by representatives of what we call the Territorial Coherence Scheme, which are in charge of spatial planning.

We hope that scientists will be able to enlighten us on the consequences of this or that scenario in terms of biodiversity, dry biodiversity but also wet biodiversity.

And so, the ALICE program is for us an opportunity to answer these challenges.

And the Blue and Green Infrastructure Networks?… How is it perceived from the SAGE point of view, of the water management?

Sylvie Le Roy – The Blue and Green Infrastructure Networks, it is indeed a concept a little new, which is resulting, at the French level, from the law.

There was the Grenelle law, then the law on biodiversity. So indeed, there is a need to take biodiversity into account in planning documents because we have a lot of biodiversity reservoirs with corridors that allow these reservoirs to be interconnected.

It went in particular through the definition of a Regional Scheme of Ecological Coherence, which defines the great networks of regional ecology.

The challenge now is to translate these reservoirs and networks to a much more local scale.

And so, in these networks, inevitably there are rivers, wetlands, the “bocage” (hedgerows and banks). These are elements that we at the SAGE (Water management body) level protect because they are important to achieve water quality goals.

But they are also important for biodiversity at large and therefore, the ALICE program must also be able to respond to: What density of all these elements must be preserved? How far not to go or risk a global collapse of biodiversity on the territory.

We are on a meshing that is necessarily impacted by the various management policies and indeed, this is part of the questions that are asked to scientists in the framework of the ALICE project.

To know what density of these elements must be conserved and how to articulate them, to design them in order to sustainably maintain biodiversity.