Hydropeaking impacts on the Dordogne river Definition of mitigation measures and assessment of their efficienc

Chanseau, Mathieu

Clave, David

Courret, Dominique

Guerri, Olivier

Lascaux, Jean-Marc

Wibaux, Benoit

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   Open Archive TOULOUSE Archive Ouverte (OATAO)  OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.  This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 11290 To cite this version : Chanseau, Mathieu and Clave, David and Courret, Dominique and Guerri, Olivier and Lascaux, Jean-Marc and Wibaux, Benoit Hydropeaking impacts on the Dordogne river Definition of mitigation measures and assessment of their efficiency. (2012) In: Eawag/Wasser-Agenda 21 Workshop on Hydropeaking, 19 June 2012 - 19 June 2012 (Zurich, Switzerland). Any correspondance concerning this service should be sent to the repositoryadministrator: staff-oatao@listes-diff.inp-toulouse.fr 1Hydropeaking impacts on the Dordogne riverDefinition of mitigation measures and assessment of their efficiencyIn alphabetical order : Chanseau M 5 , Clave D 1 Courret D 6, Guerri O 3, Lascaux JM 2, & Wibaux B 4Eawag/Wasser-Agenda 21 Workshop on Hydropeaking, Zurich, 19 June 2012Presented by Courret D (dominique.courret@imft.fr)1243 562Dordogne river• Dordogne river equipped with 5 principal dams in the upper part, organized in line (storage capacity of 970 Mm3)  200 km and 20 species affected+ 2 tributaries also equipped : Maronne and Cère riverContext : Hydroelectric schemesStudied area affected by hydropeaksRiver mean discharge : 107 m3/sMaximum turbine discharge : 340 m3/sRiver mean discharge : 20 m3/sMaximum turbine discharge : 44 m3/sRiver mean discharge : 26 m3/sMaximum turbine discharge : 52.5 m3/s301002003004005006007008002000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012Dordogne + petits af fluents  Bassin Maronne Bassin Souvigne  Bassin Vézère  Bassin Corrèze  Bassin Cère   Bassin BaveDordogne river• Reintroduction plan under progress for Atlantic Salmon : 40% to 60% of the reproduction activity of the basin.• Several fish species with high patrimonial and/or fisheries values : brown trout, grayling, dace, sculpin, planer lamprey, pike, perch, …Context : Biological stakes on the Dordogne riverNumber of large salmonid's redds per river of the basin, and per year4Dordogne river• Studies leaders :Organisms involved in partnership :• Technical operators :• Funding agencies :Territorial public institution of the Dordogne basinAssociation in charge of the management of migratory fish populationsNational agency for water and aquatic environmentsRegional public water agencyDepartmental and Regional councilONEMA R&D team Engineering firms• Hydroelectric operator :5Dordogne river• Biological surveys :• Survey of large salmonid's reproduction since 1999/2000 (MIGADO – ECOGEA)• Survey of stranding-trapping of salmonid's alevins since 2005 (MIGADO / EPIDOR – ECOGEA)• Survey of spawning and stranding-trapping of others fish species since 2006 (EPIDOR – ECOGEA)• Survey of salmonid's juveniles abundances in riffles since 2003 (MIGADO –ONEMA)• Survey of other species’ recruitment since 2010 (OMB, BAF, VAN, GOU, BRO, PER, …) (EPIDOR – ECOGEA).• Hydrology and hydropeaks characterization updated each year (ECOGEA – ONEMA R&D team).Studies and biological surveys :6Dordogne river• Hydraulic modelling of several sections, ≈ 10 km in total, keyed on the whole range of turbine flow (MIGADO – SIEE - ONEMA R&D team)Studies and biological surveys :89909192939495969798990 500 1000 1500 2000 2500 3000Distance à partir de l'aval (m)Altitude relative (m)ThalwegModèle 20 m3/sMesure 20 m3/sModèle 30 m3/sMesure 30 m3/sModèle 117 m3/sMesure 117 m3/sModèle 200 m3/sMesure 200 m3/sModèle 303 m3/sMesure 303 m3/s3D view of the Malpas sectionMeasured and simulated water level longitudinal profiles 7Dordogne river• Weekly and daily hydropeaks• Between 50 and 150 hydropeaks per year (2000-2010 period)• Mainly from October to MayHydropeaks characterizationDordogne river at ArgentatHydrogram extract0%20%40%60%80%100%120%140%160%180%200%samdim lunmarmerjeu vensamdim lunmarmerjeu vensamdim lunDayFlow (% of mean discharge)Weekly managementDaily hydropeaksDordogne river at ArgentatNumber of hydropeaks per year0204060801001201401602000 2001 2002 2003 2004 2005 2006 2007 2008 2009 20108Dordogne river• High variability of hydropeaks• Characterization useful :– To understand the impacts on fish populations– To reflect on mitigation measuresHydropeaks characterization9Dordogne river• Salmonid’s redds dewatering during returns at low flow.• Trapping of salmonid’s alevins occurring :– In channels margins during flow decreases, especially after long high flow periods– At the disconnection of secondary channels• Spawning dewatering and stranding-trapping of alevins of other fish species– On dewatered gravel bars– At the disconnection of secondary channels and backwatersBiological issues linked to hydropeaks10Dordogne river• 84 redds of large salmonid dewatered on the Dordogne river during the 2000 – 2006 period.• Redds generally located at less than 5 m from the shore, due to the rarefaction of adequate gravels, related to blockage of sediment transport by dams .Salmonid’s redds dewatering issue : Maintaining a base flow of 35 m3/s (33% of mean discharge) in winter and spring (15/11-15/06)11Dordogne river+ downgrading work on morphology of particularly sensitive sites :Salmonid’s redds dewatering issue :Before work at 32 m3/s After work at 32 m3/s% of watered reddFlow (m3/s) ≈ 95% of redds safeguarded with a base flow of 35 m3/s, instead of only 30% at the regulatory minimum flow (10 m3/s).12Dordogne river• Principally in potholes on channel margins during flow decreases, and especially after long high flow periodsTrapping of salmonid’s alevins : Limiting maximum turbine discharge to 190 m3/s (180% of mean discharge) during spring (15/03-15/06), to the extent permitted by natural hydrology.During a hydropeak at 300 m3/s Back to 50 m3/s Flow connection of 44 potholes (m3/s)13Dordogne river+ work on morphology :Before work After workTrapping of salmonid’s alevins :Deleting particularly tricky sitesWork on secondary channels’ intakes to ensure their permanent connection14Dordogne riverSpawning dewatering and stranding-trapping of alevins of other species :At 110 m3/s At 80 m3/s15Dordogne riverSpawning dewatering and stranding-trapping of alevins of others species :Sculpin spawningPerch spawning Dace eggsGrayling redds16Dordogne riverSpawning dewatering and stranding-trapping of alevins of others species :Distribution of collected fishes by species• At least 20 fish species are impacted, up to 200 km downstream the Argentat dam• Mortalities are quantitatively unmeasurable ! 17Dordogne riverSpawning dewatering and stranding-trapping of alevins of others species : Maintaining during spring (01/03-15/06) a base flow of :– 50 m3/s at Argentat (47% of mean discharge)– 80 m3/s downstream Maronne confluence (63% of mean discharge) to the extent permitted by natural hydrology Gradient of flow decrease limited to 33 m3/s/h (instead of 100 m3/s/h)Mean width (m)5055606570758085900 20 40 60 80 100 120 140 160 180 200Flow (m3/s)MalpasSaulouSaulières-RodangesSection18Dordogne riverSurvey of salmonid's juveniles abundances :It’s considered we have achieved significant improvements in abundance, notably since 2008Abundance index4 “historical” rifflesAbundance indexGroup of 8 rifflesAbundance index / reproduction activityGroup of 8 rifflesAbundance index / reproduction activity4 “historical” riffles19012345678910BAFCHAGOUVAILOFTRFCHEOBRVANGAR ABLGOUBAFVAICHELOFOBRVANCHABAFGOUVAIVANLOFGAR CHEABLBAFCHEGOUVAIABLLOFVANGAR CHAS1 S2 S3 S40500100015002000250030002010 2011 2010 2011 2010 2011 2010 2011S1 S2 S3 S4nb ind / 100 EPA+ 106 %+ 69 % + 16 % + 54 %Dordogne riverSurvey of other species’ recruitment :• 2 years of feedback to this day.• Significant response of populations to contrasted hydrology and hydropeaks regimes between 2010 and 2011.• Need to continue to learn more.Overall abundance by sectorAbundances ratio 2011 / 2010by species, on each sectorr < 0.5   0.5 < r < 0.8   0.8 < r < 1.5   1.5 < r < 3   r > 3   Upstream Downstream20Dordogne riverConclusions• A study approach taken as an example in France, combining :– hydrologic analysis, hydraulic modelling– and a very considerable effort in biological surveys on hydropeaks impacts' mechanisms and populations states• An evolutionary approach with, each year, collegial discussions between partners and the hydroelectric operator on measures for the following year Reflections on the different characteristics of hydropeaks :– Measures are mainly implemented on base flows and maximum flows– Improvements may still be possible on the gradients ?+ works on river morphology is used as a useful complement.21Dordogne riverHowever, several impacts remain to be addressed :• The reproduction of phytophil species, pike and perch especially, which are severely affected if a significant drop of water level occurs during phases of egg and fixed larvae• Seasonal stocking which can lead to early flow reductions in spring and summer and can affect :– the dynamics of upstream and downstream fish migration– the ascent of estuarine silt plug• Consequences on river morphology and habitat, due to the flood reduction and to the blockage of sediment transport :– Riverbed paving and depletion of fine grain sizes (gravels)– Increased revegetation of channel margins– Single channelization of the stream bedConclusions

Hydropeaking impacts on the Dordogne river Definition of mitigation measures and assessment of their efficiency

http://oatao.univ-toulouse.fr/11290/1/Courret_11290.pdf

Hydropeaking impacts on the Dordogne river Definition of mitigation measures and assessment of their efficiency

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