DS#6 - "Vienne river" (France)

The case study in 5 minutes

Location

The demonstration site, the Vienne River basin, is located in the central part of France.

Description of the area

Biogeographical region: Atlantic
Landscape context: Rural agricultural
Total area: 21 157 km²
Land cover: 50 % woodland, 45 % agricultural aera, 10 % wetlands
Population Density: ~21 inhabitants/km²

Climatic Challenges

Climatic

Planned activities

In DS#6, three types of NBS will be implemented and monitored;

1. Removal of artificial water bodies (ponds) in the beds of watercourses,
2. Removal of drains in wetlands
3.Restoration of riparian forest by cutting coniferous trees and planting species adapted to humid environments. These NBSs will benefit from a scientific monitoring covering several aspects such as hydrology, pedology, geomorphology, biodiversity, etc.

DS#6 partners will be supported in their actions by stakeholders involved in the SEA programme, who will be able to share their knowledge, give advice, follow operations, etc. These exchanges will be facilitated by the introduction of a NATALIE section on the various SEA committees (technical committee, steering committee, and scientific commission).

This integration of local stakeholders into the processes and the work carried out jointly with FL#6 and the other WPs, particularly WP2 and WP6, must give a solid basis for strengthening the deployment of NBSs in the Vienne River basin.

Progress

The first year was used to select 7 sites for the NBSs implementation. These sites have been the subject of agreements with the owners or purchases. Then, the monitoring to establish the initial states have been designed through bibliography and consultation of companies. Finally, the monitoring has been implemented: flows monitoring, water temperatures monitoring, fauna & flora inventories, landscape evolution monitoring, etc. These steps are the starting point to quantify the contribution of NBSs to climate change adaptation. Without these steps, it would be impossible to prove the benefits of such measures.

The beginning of the NATALIE project’s second year was devoted to the NBSs designing and obtaining the necessary authorisations for their implementation. Six of the seven sites selected have a pre-work study completed and, for five sites, public consultations for the works are in under way or have been completed.

This second year is also an opportunity to step up communication about our actions, in particular with the production of the first 2 episodes of our series dedicated to the NATALIE project. Discover our series here.

Ambition

Ambition during the project

The ambition is to demonstrate the effectiveness of the three NBS types in improving water flow and water quality using evidence-based knowledge.

Ambition after the project

Because wetlands restoration can be a very long process, improvements on hydrology should continue beyond the lifetime of the project. Furthermore, it is expected that the NATALIE NBS will be examples that will be followed by stakeholders at a larger scale.

Questions

In France, some ponds are larger than 500 m² and ranging in depth from one to few meters. Most of these ponds are artificial and strictly ornamental.
In the Vienne River basin, ponds have been developed by creating multiple dams on the watercourses, breaking their continuity and preventing wildlife and sediments from passing through normally. They are also a major source of evaporation during the summer months, reducing flows which may cause dry steams.

Restoring watercourses by removing ponds built as dams allow to reduce evaporation, increase flows and make wildlife and sediments circulate again! It’s a crucial challenge as the over-evaporation of ponds in Vienne River basin is estimated equalled to drinking water withdrawals. With climate change, this evaporated water will be needed to maintain stream ecosystems, domestical, industrial, and agricultural uses.

Regarding biodiversity, few ponds (dams) are shallow and allowing vegetation to develop, but most of them are too deep to welcome a rich biodiversity, making them less interesting than very small ponds disconnected from watercourses.

In the Vienne River basin, ditches or underground pipelines are used to drain wetlands in order to plant coniferous trees, cultivate the land or feed livestock. These drained wetlands can no longer ensure their ecological functions, including their hydrological functions, which leads to water flow problems. Filling in ditches slows down water flow and improves its storage within wetlands, which release it back into watercourses during low-water periods. Restoring wetlands then helps to maintain their rich and unique biodiversity, while making the water cycle more resilient to climate change.