Four weir removals on the Tardoire, France
Tardoire river (Charente River basin), Haute-Vienne, France, 2022-2023
The Tardoire, a watercourse in 1ère piscicultural category, from its source in the commune of Châlus to the brook of Suchés, is classified list 1 and list 2 under article L.214-17 of the environmental code. With a total length of 114 km, it drains a catchment area of 1200 km². Part of the spring is tapped for drinking water supply. It flows on a crystalline base up to Montbron and then on limestone soil where it loses part of its water in the chasms (karst).
All hydraulic structures on this watercourse are concerned by this regulation in order to ensure ecological continuity.
Within the OPEN RIVERS Programme, and in partnership with ERN, the SYMBA Bandiat-Tardoire has taken on the role of project manager for the restoration of ecological continuity on 4 structures on the Tardoire. These structures were selected because they have the greatest impact on ecological continuity and the quality of the environment (large size of the structures, long zones of influence, etc.).
CONTEXT AND OPPORTUNITY
The alteration of the hydromorphology of the Tardoire and the disruption of ecological continuity have been targeted as degrading factors of the ecological status of the aquatic environment. In order to achieve the objectives of good status and also to support the owners, the SYMBA Bandiat-Tardoire has carried out a global study for the restoration of ecological continuity on 13 structures of the Tardoire from 2017 to 2020.
These sites are located on the “Tardoire” water body, classified as having a medium ecological status with a good status objective for 2027 (SDAGE 2022-2027).
The Tardoire is a major issue for the European eel.
The owners are in contact with SYMBA for several years and they have given their trust for this project. The site of the Buisson forge with a weir having a head of 2.6 m is very representative of the cumulative impact of disorders (incision, upstream sediment accumulation, fish continuity, upstream tributary connection, etc.).
Other actions have been and are being carried out by the syndicate, such as the restoration of wetlands, the removal of water bodies, etc., which also contribute to achieving good water status. The future watercourse management programme currently being drawn up will tend towards similar actions with the common objective of good water status.
OBJECTIVE OF THE PROJECT
The removal will significantly improve the morphology and natural functionality of the Tardoire (facies alternation, sediment transport). As a result, it will improve aquatic habitats, which will be more diversified and better oxygenated, and water quality by acting on parameters such as temperature and the dilution factor.
The project will also allow the free migration of fish species in the river.
The target species identified are
– Amphihaline species: European eel (Anguilla anguilla)
– Holobiotic species: Brown trout (Salmo trutta)
The removal of these structures will free up a significant 18.60 km of watercourse for these 4 structures; in conjunction with the removal of the weir directly downstream carried out in 2017 (Puybonland mill); and also allow reconnection with the tributary La Colle (over 3.20 km).
Overall, the ecological status of two bodies of water, “La Tardoire from the confluence of the Colle to the confluence of the Bonnettes” and “Ruisseau de la Colle”, will be improved, as well as the ZNIEFF.
AT A GLANCE
– Location: Communes of Chéronnac and Champagnac-la-rivière in the Haute-Vienne department (87), France
– The river: The Tardoire
– Open line : 18.60 km and reconnect 3.2 km of the river with its tributary, the Colle.
– Key Habitats: Category 1 river, medium width (about 6 metres)
– Target species: Brown trout (Salmo Trutta), European eel (Anguilla Anguilla)
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