Ecological engineering. Wetland buffer zones: their success is far from artificial !

Your team has just co-published with Onema a technical guide on the implementation of artificial wetland buffer zones. What was the idea behind it ?

Julien Tournebize, hydrologist at Irstea : In France, there are guides on the implementation of dryland buffer zones, but not wetland buffer zones. The idea behind this guide [1] was to share our knowledge and experience on 5 wetland zones, including the pilot site in Rampillon: 1.4 hectares implemented since 2012. We wanted to contribute to general reflection on the subject.

We were the first to work on the question of pesticides in agricultural drainage water since the European Artwet Project [2] in 2006. Research conducted in New Zealand and in Northern Europe - Sweden and Denmark - did precede our work on artificial wetland buffer zones, but it focused much more on nitrates. We've since caught up.

The guide is designed for managers, design consultancies, farmers... basically anyone who wants to implement buffer zones around drained catchment areas. What does it contain ?

J. Tournebize: Firstly, it contains a methodology and the various phases needed to implement these artificial wetland buffer zones including hydrological, topographical and area diagnoses. Preliminary studies that need to be carried out are also included, for example, geotechnical studies into soil quality, some precautionary measures, recommendations (plant types, maintenance) and legal issues. How to size the wetland buffer zone is also addressed, although not in detail : this is a technical implementation guide rather than a sizing guide. That will perhaps be the next phase.

In France, ecological engineering is recognized as one of the "strategic pillars of the green economy" by the Ministry of Ecology, Sustainable Development and Energy. The Rampillon artificial wetland buffer zone won the National Grand Prize for Ecological Engineering last October. What did this represent in terms of recognition for Irstea expertise ?

J. Tournebize: A dozen projects had been submitted in the "Ecological engineering against agricultural diffuse pollution" category so yes, this award was indeed significant in terms of recognition for Irstea's work ! Members of the jury appreciated the exemplary nature of the project, especially in terms of the implementation efforts to reproduce this type of buffer zone.

In particular, this technical and scientific recognition makes our exchanges with colleagues and partners (farmers, companies, etc.) a little easier.

For more information

Ecological engineering: a double win for Irstea

You recently worked with Estonian researchers on site in Rampillon (Seine-et-Marne). Was the aim once again to share knowledge ?

J. Tournebize: Yes, of course, and also to complete our current research. As part of our strategy and in order to evaluate the effectiveness of the systems, it was necessary to include negative aspects and limitations, such as greenhouse gas emissions.

Setting up a weather station in a wetland buffer zone © Irstea / J. TournebizeThe partnership with the University of Tartu in Estonia was set up following a discussion with one of our researchers [3]. They had resources we were interested in : the device in question makes it possible to measure greenhouse gas emissions from artificial wetland buffer zones. We therefore benefited from Estonian know-how, with greater focus on gas emissions rather than artificial wetland buffer zones and pollution management aspects. This makes sense as they have natural, peat-based wetlands in their region.

Several exchanges were organized throughout the year, making it possible for us to supplement existing data. On their side, they were able to transpose their methods onto new aquatic systems. It was an extremely positive collaboration! In fact, they should be coming back for a 3rd mission in 2015.

You were also invited to China in April 2014 to provide ecological engineering training to Chinese researchers. Are artificial wetland buffer zones being built in China ?

J. Tournebize: They are definitely interested. Currently there is an ANR-China project proposal on the table, which would continue to evaluate the Rampillon site and then transfer the system to China. It is a co-funded project.

International exchanges, publications, welcoming the general public during the 2nd National Ecological Engineering Event, the prize and now the publication of a technical guide: how will you focus your research after the year you had in 2014 ? Will the success of artificial wetland buffer zones be confirmed ?

J. Tournebize: In order to reduce pesticide transfers on French drainage areas (3 million hectares), we would need 30,000 hectares of artificial wetland buffer zones ! This raises several questions about how to optimize water flow interception strategies and modeling. The question of scaling should also be addressed, particularly at a sociological rather than technical level: we have to see things from a decision-maker's perspective. How can we facilitate the rollout of buffer zones ? And how can we raise awareness of the policies ?

We are working with teams from the Irstea center in Montpellier to address this [4]. Some barriers, such as regulations and financial recognition on land rights-of-way for non-cultivated farmland, need to be removed. A role-play scenario was developed for farmers on this topic. Interactive workshops have also been organized within the technical buffer zone group at Onema, of which Irstea is a member.

Overall, our research will have to integrate seasonal variability into system effectiveness. Sizing aspects must also be improved. However, we are still dependent on funding: for example, the Rampillon pilot project is coming to an end in October 2015.

Consult the guide online (in french).

For more information

[1] Technical guide for the implementation of artificial wetland buffer zones to reduce the transfer of nitrates and pesticides in drainage water. Funded by Onema. In collaboration with the Seine et Marne Departmental Directorate of Land Use. Authors: Julien Tournebize (Irstea - project coordinator), Cédric Chaumont (Irstea), Adrien Marcon (Irstea), Sophie Molina (DDT 77) and Daniel Berthault (DDT 77).

[2] The European Artwet Project (2006-2010).

[3] Ulo Mander, a specialist in landscape ecology from Estonia, is currently working on site on Julien Tournebize's team at the Irstea Antony center.

[4] Water resource management, actors and uses (G-EAU) joint research unit and Lisode (Minéa start-up in SHS – Participative decision processes)