Tests for evaluating the injuries suffered by downstream ... · 4.1. The Tarn River 4.1.1. General...

Tests for evaluating the injuries suffered by Atlantic salmon smolts in their transiting through the VLH turbogenerator unit

E.CO.G.E.A. for F.M.F., April 2008.

Tests for evaluating the injuries suffered by downstream-migrating salmonid juveniles and silver eels in their transiting

through the VLH turbogenerator unit installed on the Tarn River in Millau

- Tests of February 2008 on Atlantic salmon smolts.

Contracting organization:

Name: ,

Address: 10, avenue de Toulouse 31860 PINS-JUSTARET - FRANCE

Telephone / Fax: 05.62.20.98.24

E-mail: [email protected]

Contact: Thierry Lagarrigue

Writer(s):

T. Lagarrigue, B. Voegtle and J.M. Lascaux.



Acknowledgements:

As many studies of this type, the tests have required the contribution of many people.

The authors would thus especially like to thank:

• Michel Larinier, head of the ONEMA-CEMAGREF-INPT technologies research team "Restauration de la continuité écologique des cours d'eau à poissons migrateurs" (Restore the ecological continuity of water streams with migrating fish), which has greatly contributed to the success of this study by his experience of this type of follow-up,

• Jacques Fonkenell and Marc Leclerc, respective managers of FMF et MJ2 companies, who have provided all possible means to make the study successful,

• Dominique Courret, of the GHAAPPE (Groupe d’Hydraulique Appliquée aux Aménagements Piscicoles et à la Protection de l’Environnement: Group for Hydraulics Applied to Pisciculture Development and Environmental Protection), for his help and his perspicacity during the tests,

• Christian Brengues, for his availability and all the work done in building the different technical devices used in this study.



INDEX:

1. Introduction ....................................................................................................................... 1

2. Objectives of the study....................................................................................................... 2

3. Partners of the study.......................................................................................................... 2

3.1. Financial partners .................................................................................................... 2

3.2. Scientific and technical partners............................................................................. 2

4. Site of the study.................................................................................................................. 3

4.1. The Tarn River ......................................................................................................... 3 4.1.1. General description ............................................................................................ 3 4.1.2. Flow data for the Tarn river ............................................................................... 3

4.2. The Troussy Mill development in Millau............................................................... 4 4.2.1. Characteristics of the development .................................................................... 4 4.2.2. Fish passes.......................................................................................................... 5

5. Description of the employed device................................................................................... 6

5.1. Smolt injection device .............................................................................................. 6

5.2. Smolt recovery installation...................................................................................... 7

6. Biological material ............................................................................................................ 8

6.1. Origin of the smolts .................................................................................................. 8

6.2. Storage of the smolts ................................................................................................ 8

6.3. Characteristics of the used smolts........................................................................... 9

7. Implemented experimental protocol ............................................................................... 10

7.1. Origin of the implemented protocol ..................................................................... 10

7.2. Tested injection points ........................................................................................... 10

7.3. Composition of the different tested batches......................................................... 11

7.4. Typical smolt release process ................................................................................ 11

8. Testing conditions............................................................................................................ 12

8.1. Tarn water temperature ........................................................................................ 12

8.2. Turbine operating rate during the tests ............................................................... 12

9. Results.............................................................................................................................. 14

9.1. Recapture rate ........................................................................................................ 15

9.2. Assessment of the mortality rates ......................................................................... 15 9.2.1. Gross and corrected immediate mortality rate ................................................. 15 9.2.2. Deferred mortality ............................................................................................ 17 9.2.3. Effect of the injection point.............................................................................. 17 9.2.4. General mortality rate of the VLH turbine....................................................... 17

9.3. Nature of the observed injuries............................................................................. 19

9.4. Other species captured during the tests ............................................................... 20



10. Discussion........................................................................................................................ 21

11. Conclusions - Prospects .................................................................................................. 25

12. Bibliography .................................................................................................................... 26

APPENDIXES


E.CO.G.E.A. for F.M.F., April 2008. 1

Tests for evaluating the injuries suffered by downstream-migrating salmonid juveniles and silver eels in their transiting

through the VLH turbogenerator unit -

Tests of February 2008 on Atlantic salmon smolts.

1. Introduction

The European Water Framework Directive (directive 2000/60/CE), operative on December 22, 2000, sets a framework for Community action in the field of water policy. Among the defined priority objectives, the restoring of the ecological continuity, which can be defined as the free circulation of biological species and the proper conduct of the natural transportation of sediments, especially requires limiting as much as possible damages linked to the downstream migration of fish at the level of hydroelectric power plants.

The issue of downstream migration essentially concerns so-called “highly migratory” fish species for which part of the biological cycle necessarily implies a long upstream migration where they are likely to cumulate the impacts encountered all along their migration path (crossing of many developments). Some of the most especially vulnerable among said species are juvenile Atlantic salmons (Salmo Salar L.) and sea trouts (Salmo Trutta L.) which perform a downstream migration from the upstream parts of rivers, as well as adult seaward-migrating European eels (Anguilla anguilla L.) (called “silver eels”), which, due to their size, are likely to suffer significant injuries as they transit through turbines.

Currently, the research and development efforts to solve the problems posed by the downstream migration at the level of hydroelectric developments bear on 3 main types of solutions (COURRET and LARINIER, 2007):

• Constructions of so-called "fish-friendly" water intakes with an associated downstream migration device letting the individuals transit downstream of the development without injuries,

• Partial or full stop of the turbine operation during the preferential downstream migration period of the targeted species,

• Installation of specific so-called "fish-friendly" turbines to replace the existing turbines or on new developments (generally still unharnessed low-head sills).

This last solution has been chosen by the Forces Motrices de Farebout Company, which exploits the existing water fall on the Tarn River in Millau, at the place named Troussy. Indeed, a totally new machine, the VLH turbine (Very Low Head turbine), supplied by MJ2 Company, has been installed for the turbine operation on this demonstration site. From the origin, the main “fish-friendly” criteria known to date relative to the passing of fish through turbines have been taken into account among the basic data for the design of the VLH.



One can especially mention:

• A large runner diameter (4.5 m) creating large spaces between guide blades and between blades, allowing the passing of fish,

• A small runner rotation speed (on the order of 40 cpm),

• Water velocity inside the runner < 2 m/s,

• Very small pressure variations.

Based on a theoretical study analyzing the “fish-friendly” criteria of the VLH, the concerned services of the Aveyron Department have granted an operating license for the Troussy fall for a 30-year time period (prefectural authorization of January 16, 2006), without prior installation of a downstream migration device, provided to perform in-situ tests intended to confirm or not the results of the theoretical study.

2. Objectives of the study

The study started in 2007 thus aimed at performing the in-situ tests to assess the fish-friendliness of the VLH by an analysis of the injuries suffered by downstream-migrating salmonid juveniles and silver eels in their transit through the turbine.

Downstream migration pretests have been carried out in April 2007 on Atlantic salmon juveniles (LAGARRIGUE and LASCAUX, 2007). Silver eel downstream migration tests have been carried out in December 2007 (LAGARRIGUE et al., 2008).

The present document accounts for the new Atlantic salmon juvenile downstream migration tests carried out in February 2008.

3. Partners of the study

3.1. Financial partners

The Millau demonstration site as a whole has benefited from a financial aid of the A.D.E.M.E., given to the Forces Motrices de Farebout (FMF). On this account, the fish-friendliness tests have received a contribution of approximately 20% of their total cost, the balance being financed by FMF.

3.2. Scientific and technical partners

• The scientific follow-up of the tests, from the defining of the experimental protocol to the carrying out of the tests and to the exploitation of the results, has been performed by Michel Larinier, head of the ONEMA-CEMAGREF-INPT technologies research team “Restauration de la continuité écologique des cours d'eau à poissons migrateurs”,

• The logistics to prepare the tests and the management of the production installation have been taken care of by Jacques Fonkenell and Marc Leclerc, managers of FMF and MJ2, respectively,

• The technical part of the tests has been taken care of by the E.C.O.G.E.A. research department.



4. Site of the study

4.1. The Tarn River

4.1.1. General description

Considering the Dordogne as a main river, the Tarn is the largest affluent of the Garonne. Its source is located on the Mount Lozère and it flows into the Garonne from the right bank close to Castelsarrasin. The Tarn River is submitted to a Mediterranean and oceanic pluvio-nival regime. It has very strong seasonal flow variations with floods in the winter and spring, and a marked low water from July to September.

All along the 50 km of gorges located upstream of Millau, the Tarn has but one main affluent, the Jonte. However, it receives many sources and resurgences originating from bodies of groundwater of the karstic systems located under the neighboring limestone plateaus or “causses” (Sauveterre Causse and Méjean Causse) which provide it with substantial water complements.

4.1.2. Flow data for the Tarn river

On the area involved in our study, flow data issued by the Banque Hydro (French hydrology databank) are especially available on the Tarn river at Mostuéjouls (Station N°03141010 located downstream of the confluence with the Jonte, approximately 17 km upstream of the Troussy mill) and on the Tarn river in Millau (Station n°03401010 located downstream of the confluence with the Dourbie).



Tarn at Mostuéjouls Station n°03141010

Data calculated over 95 years (1913 - 2007)

Tarn in Millau Station n°03401010

Data calculated over 38 years (1969 - 2007)

Catchment area 925 km² 2 170 km²

Altitude (French leveling network) 388 m 349 m

Interannual average flow rate 31.6 m3/s 47.3 m3/s

QMNA5 (minimum discharge over five years) 5.7 m3/s 8.8 m3/s

10-year return flood (daily flow rate) 680 m3/s 1 100 m3/s

50-year return flood (daily flow rate) 950 m3/s 1 600 m3/s

In Millau, the interannual average flow rate of the Tarn River close to the confluence of the Dourbie, and upstream thereof, is of 47.3 m3/s for a 2170 km2 catchment area.

The average flow rate at the Troussy Mill is estimated to be 36 m3/s.

4.2. The Troussy Mill development in Millau

4.2.1. Characteristics of the development

The Troussy Mill development is comprised of a stonework dam which diverts part of the Tarn waters to the reach of the mill where the VLH turbine is implanted.

The Troussy Mill site in Millau

The Millau installation has the following main characteristics:

• Head height 2.5 m,

• Maximum water discharge of 20 m3/s, that is, approximately 56% of the average flow rate,

• Maximum electric power of 410 kW,



• VLH turbine 4500 with an 8-blade variable-opening Kaplan-type runner, of a 4.5-m diameter, rotating at 40 cpm.

A description of the VLH concept and the layout plan of the machine which shows the main arrangements of this development can be found in the appendixes.

4.2.2. Fish passes

In the Aveyron Department, the Tarn River is classified as a Reserved River (section 2 of the 1919 law relative to the use of hydropower) upstream of its confluence with the Dourbie in Millau and as a Migratory River (section L.432-6 of the French environmental code) with no associated list of species (these classifications are likely to be modified by the application of the French law on water and aquatic environments of December 30, 2006).

As to the free circulation of fish at the Troussy development level, the spawning run of salmonid species and of freshwater cyprinids will be ensured by a pool and notch fish way (7 pools with a lateral notch and a bottom hole) implanted on the left bank of the Tarn, which should be operational in 2008. For the downstream migration, no specific device is provided, subject to in situ tests (which are in particular the object of the present report) demonstrating “acceptable” mortality rates for the fish species transiting through the turbine.



5. Description of the employed device

The device employed for this study is formed of two main parts: a device for “injecting” the smolts into the turbine and a device for recovering the individuals at the turbine outlet.

5.1. Smolt injection device

Even though it is of smaller size, the principle of the injection device used in Millau takes its inspiration from different tests, and especially those performed in Quebec on the Saint-Laurent River (DESROCHERS, 1995; THERRIEN, 1999). It was originally designed to carry out the December 2007 tests on silver eels (LAGARRIGUE et al., 2008), and has been used again for the tests on smolts.

It is formed of a water tank containing a fish sample, connected to a PVC tube (∅ 200 mm) enabling directly injecting them at the level of the turbine guide blades, which avoids having to release them after nightfall in the head race upstream of the turbine and waiting for them to swim down the machine by themselves.

For the injection, the tank plug is removed, letting out the water and part of the smolts “head first”, the remaining individuals being manually forced to enter the PVC tube.

Water tank connected to the PVC tube enabling injection of the smolts directly at the level of the turbine

guide blades (on these pictures, at mid-blade)

View of the PVC injection tube at the periphery close to the turbine guide blades, of a "rake" of the raking

system and of the installed observation camera.



5.2. Smolt recovery installation

The smolt recovery installation, improved after the first experiments carried out in Millau on smolts in spring 2007 (LAGARRIGUE and LASCAUX, 2007), is identical to that used for the December 2007 tests on silver eels (LAGARRIGUE et al., 2008).

It is formed of a 6 x 3-meter metal frame, placed at the turbine outlet, set in reserved grooves on the concrete side walls and supported by a concrete floor (to limit as much as possible the risk of individuals escaping at the turbine outlet).

Frame supporting the net resting on the concrete floor

This frame supports a knotless polyamide net which is very flexible and non-abrasive for the fish (see appended plans). It is formed of 3 decreasing meshes (27, 15, then 10 mm) and is approximately 14 meters long (4 m less than for the tests with smolts of April 2007).

The net is provided with stiffeners to maintain the pocket open until it emerges into a fish box (dimensions of 1.5 x 1 x 1 meter – see appended plans) enabling housing and recovering the fish. The fish box is attached to a floating pontoon and is maintained immersed by 2/3. The entrance is provided with a non-return system to avoid for the fish to leave the fish box once they are inside. It has a hinged lid and is dressed with a 10-mm mesh knotless polyamide net. The travels between the bank and the pontoon are performed by means of an inflatable boat.

Complete recovery installation in place Floating pontoon and fish box linked to the immersed

net

Once they have been recovered with a hand net from the live well, the smolts are conveyed to the housing in plastic bins (distance of approximately 80 m to be traveled).

The recovery installation is installed by means of a crane. The pontoon supporting the fish box is the first to be put into the water. Then comes the frame, after which the net and the fish box are connected.



Installation of the pontoon and of the fish box by

means of the crane Installation of the frame and of the net by means of the

crane

6. Biological material

6.1. Origin of the smolts

The smolts have been bought from Patrice Astre’s fish farm: the Ferme du Ciron in Allons (47).

They have been conveyed to Millau on the 26/02/2008 in a truck provided with 2 tanks equipped with an oxygen supply device.

6.2. Storage of the smolts

The smolts have been stored in 3 circular tanks (capacity of 600 liters each), as well as 2 rectangular tanks (capacity of 100 liters each) continuously supplied with Tarn water by 2 circulation pumps immersed in the Tarn upstream of the Troussy water intake. The tanks have been installed in the underground of the Troussy mill (cool and dark) just above the water passage.

2 of the 3 circular smolt storage tanks and their water

supply in the Troussy mill Smolts in one of the circular tanks

The physico-chemical characteristics of the Tarn water supplying the tank measured on the 26/02/2008 are disclosed in the following table.



Tarn water supplying the tanks

pH 8.2

Conductivity 262 µS/cm

Dissolved oxygen 10.7 mg/l

(99.7% sat.)

Temperature at 2:30 pm 9.9°C

6.3. Characteristics of the used smolts

As a whole, 1,218 smolts have been used during the tests. We have chosen to carry out the tests at the very beginning of the smoltification period so that the individuals would not be too fragile (as had been the case for the April 2007 pre-tests). Hence, most of the individuals exhibited signs of a starting smoltification (color change, loss of a few scales, increased agitation) but their general health state was very satisfactory. Thus, no mortality has been observed during the transportation between the fish farm and Millau (5 hours of travel) and only 2 individuals have died between their arrival in Millau on the 26/02/2008 at 1:30 pm and the beginning of the tests on the 28/02/2008 at 10:00 am.

The total length Lt (to within one mm) has been assessed over a sample of 126 individuals.

0%

5%

10%

15%

20%

25%

30%

[140

;150

[

[150

;160

[

[160

;170

[

[170

;180

[

[180

;190

[

[190

;200

[

[200

;210

[

[210

;220

[

[220

;230

[

[230

;240

]

The smolts are between 147 and 240 mm long, for an average 199 mm (median of 200 mm). Their average weight assessed over a sample of 30 individuals is 90 g (it varies from 34 to 150 g according to individuals).

No size class has been distinguished, given, in particular, the large dimensions of the turbine (with a 4.5-m diameter) allowing large intervals between guide blades and between blades and thus with an effect of the size on the smolt mortality which is probably limited, or even null.



7. Implemented experimental protocol

7.1. Origin of the implemented protocol

The protocol developed for this study, identical to that used for the pre-tests carried out on smolts in spring 2007 (LAGARRIGUE and LASCAUX, 2007) and for the tests on silver eels carried out in December 2007 (LAGARRIGUE et al., 2008), is widely inspired from the experimental protocol developed in the late 1980’s based on the return on experiences carried out on a few rivers in France (DARTIGUELONGUE and LARINIER, 1987; LARINIER and DARTIGUELONGUE, 1989) and abroad (MONTREAL ENGINEERING COMPANY, 1981 and 1982; KYNARD et al., 1982; GLOSS and WALH, 1983; BELL and KYNARD, 1985; MONTEN, 1985). It consists of introducing the fish close to the runner inlet and recovering them immediately by filtering all the turbine output flow by means of a net.

7.2. Tested injection points

During the December 2007 tests on silver eels (LAGARRIGUE et al., 2008), the eel injection at 3 points has enabled showing that the mortality rate was zero close to the hub, intermediary at mid-blade, and maximum at the runner periphery (approximately 5 times greater than at mid-blade) and that this mortality increase from the hub to the blade tip, already shown on Kaplan turbines (see CADA’s synthesis, 2001), is essentially linked to the presence of a severing area located between the discharge ring at the end of the blades and the blade tips.

Since the level of the runner at which smolts in “natural” seaward migration are likely to engage was not known beforehand, we have thus also attempted to know whether the mortality observed on smolts would distribute uniformly along the blade axis, by using the 3 injection points already tested on silver eels, that is: at the runner periphery (close to the end of the blades and to the discharge ring), close to the hub, and at mid-blade.

Injection point n°1: "periphery"

Injection point n°2: "hub"

Injection point n°3: "mid-blade"



7.3. Composition of the different tested batches

5 different batches have been tested

• A “control” batch: the “control” batch is formed of 200 smolts and undergoes the same manipulations as the “conventional test” batches except for the passing through the turbine (they are injected immediately downstream of the turbine, directly into the net). Thus, this batch enables appraising the impact of the method (transportation, handlings, housing conditions), as well as of the injection and recovery material,

• A “dead smolt” batch: the “dead smolt” batch is formed of 118 smolts killed just before the release and aims at appraising the efficiency of the recovery device for dead individuals to take into account a possible difference between the recapture ratios of dead fish and of live fish,

• Test batch n°1 – Periphery: test batch n°1 is formed of 300 smolts and has been injected at the runner periphery (close to the end of the blades and to the discharge ring),

• Test batch n°2 – Hub: test batch n°2 is formed of 300 smolts and has been injected close to the runner hub.

• Test batch n°3 – Mid-blade: test batch n°3 is formed of 300 smolts and has been injected at mid-blade.

7.4. Typical smolt release process

In the late morning or in the early afternoon, the smolt batch to be released is cautiously recovered from its appointed storage tanks. The fish are brought in several goes into containers filled with water on the right-bank side wall and poured into the container connected to the injection tube. Once the turbine speed is steady at full power and full opening, the tank plug is removed and the smolts are “injected” via the PVC tube directly at the level of the turbine guide blades.

In the times following the injection, smolts end up in the recovery net after having transited through the turbine. The turbine speed is then lowered to be able to immediately recover the individuals in the floating fish box by means of a hand net. The recapture rate being under 100%, a “flushing” of a few minutes is performed by raising the turbine speed to force the largest number of individuals present in the net to proceed down to the fish box. Finally, to avoid as much as possible to mix the different used batches and to be sure that no individual remains in the net, the net is completely taken out of the water with the crane to be totally emptied of its content.



Complete lifting of the net at the end of the test to totally empty it

While the other captured species are immediate put back into the water, the smolts are taken back in containers into their storage tank in the mill. They are counted and observed one by one to spot possible injuries (bruises, scratches, severing, injured vertebral column…). The live individuals are kept in their storage tank to have their behavior observed for a period from 72 to 96 hours according to the batches for assessment of a possible deferred mortality.

8. Testing conditions

The tests have been carried out on February 28 and 29, 2008.

8.1. Tarn water temperature

The Tarn water temperature during the tests ranged between 9 and 11°C according to the day and time of the measurement.

8.2. Turbine operating rate during the tests

The preferential smolt downstream migration period in the southern part of Europe is in spring, generally from March to May (BAGLINIERE, 1976; BŒUF, 1994; CHANSEAU et al., 1999). It takes place in essentially nocturnal steps, following flow rate increases (“water inrushes”).

Tarn flow rate at Mostuéjouls(data calculated over 95 years – from 1913 to 2007)

0

5

10

15

20

25

30

35

40

45

50

January February March April May June July August SeptemberOctober NovemberDecember

Flow rate (m3 /s)



During this period of the year, the Tarn flow rate is generally greater than the maximum discharge of the Troussy Mill (maximum turbine discharge of 20 m3/s, that is, approximately 56% of the module). Thus, we have chosen to carry out the tests with the most current turbine operating rate in such strong flow conditions at the preferential smolt migration period, that is, at full opening and full power (rotation speed of 40 cpm and P = 410 kW).



9. Results

Synthesis of the main results:

Number of smolts Immediate mortality rate Date Time Test batch Injection point

injected recaptured dead

Recapture rate

gross corrected

Deferred mortality

28/02/08 10:00 am "Control" Downstream of the

VLH 200 193 0 96.5% 0 - 2.1%

29/02/08 1:00 pm "Dead" 118 114 - 96.7% - - -

28/02/08 11:30 am N°1 300 272 16 90.7% 5.9% 5.5% 1.5%

28/02/08 4:00 pm N°2 300 287 3 95.7% 1.1% 1.0% 1.0%

29/02/08 10:00 am N°3 300 262 4 87.3% 1.5% 1.4% 1.6%

The details of the calculations of the different mortality rates disclosed in this table are given hereafter.

mid-blade

periphery

hub

mid-blade



9.1. Recapture rate

Taux de recapture0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Lot "Témoin"

Lot "morts"

Lot test n°1-périphérie

Lot test n°2-moyeu

Lot test n°3-mi-pale

The recapture rate for the “dead” smolt batch is high (96.7%). This thus leads to assume that most of the fish in the test batches which have not been recaptured are alive.

However, this recapture rate remains smaller than 100%, as for the “control” batch (96.5%) and for the 3 test batches (it varies from 87.3 to 95.7% with an average 91.2%). Thus, despite the complete filtering of the turbine discharge, the fact that we have never recaptured all the injected smolts probably reflects the presence of holes in the net, of paths under frame supporting the net and/or of water recirculation areas where the fish (dead or alive) can stay, despite the “flushings” performed at the end of the injection of each batch by a decrease followed by a fast increase the VLH power.

9.2. Assessment of the mortality rates

9.2.1. Gross and corrected immediate mortality rate

9.2.1.1. "Control" batch

No immediate mortality has been recorded for the “control” batch, which proves the neutrality of the smolt injection and recovery methods on the observed mortalities.

9.2.1.2. Test batches

• Gross immediate mortality rate:

Calculation mode: Since the dead fish recovery is high but not total, the gross immediate mortality rate has been calculated as the ratio of the number of recovered dead smolts to the total number of recaptured smolts.



• Corrected immediate mortality rate:

Calculation mode: As recommended by LARINIER and DARTIGUELONGUE (1989), given that no immediate mortality has been observed in the “control” batch, the gross immediate mortality rate has only been corrected to take into account the recapture rate difference between live smolts and dead smolts, by using the following formula.

Corrected immediate mortality rate = Rm / Nb x Trm

with:

Rm, the number of dead smolts taken out of the net, Nb, the number of injected fish, Trm, the dead smolt recapture rate.

Taux de mortalité immédiat

0%

1%

2%

3%

4%

5%

6%

7%

8%

moyeu mi-pale périphérie

Point d'injection

Taux

de

mor

talit

é (%

)

Brut

Corrigé

The gross immediate mortality rate is 1.1% close to the hub, 1.5% at mid-blade and 5.9% at the runner periphery. After correction, the corrected immediate mortality rate becomes 1.0% close to the hub, 1.4% at mid-blade, and 5.5% at the runner periphery.



9.2.2. Deferred mortality

Mortalité différée

0.0%

0.5%

1.0%

1.5%

2.0%

2.5%

Lot "Témoin" Lot test n°2-moyeu

Lot test n°3-mi-pale

Lot test n°1-périphérie

Mor

talit

é di

fféré

e (%

)

After from 72 to 96 of housing of the different batches, the deffered mortality of the “control” batch, linked to the smolt housing conditions, is low, while being greater than that of the test batches: it is of 2.1% versus 1.4% in average for the test batches (varying from 1.0 to 1.6%). Thus, the deffered mortality of the test batches linked to the transiting through the VLH (consequences of a shock, of a severe abrasion…) has been considered as negligible.

9.2.3. Effect of the injection point

The immediate mortality rates observed between the “mid-blade” injection and the “hub” injection are not significantly different (p = 0.156). However, the immediate mortality rates are higher with an injection at the runner “periphery” (p = 0.000).

9.2.4. General mortality rate of the VLH turbine

An assessment of the general mortality rate of the machine for smolts has been performed with the same considerations as for the tests on silver eels (LAGARRIGUE et al., 2008), that is:

• The flow rate distribution from the machine inlet to the runner is homogeneous, that is, the elementary flow channels distribute in the same way between the inlet of the machine, that of the distributor, and the runner passage,

• Perpendicularly to the runner, the meridian velocities (components measured along the rotation axis of the machine) are constant (in the case of “efficient” machines).

It can thus be estimated that to each injection point has a corresponding elementary liquid ring with a surface area proportional to the average diameter of the considered ring and that the flow rate of this ring is also proportional to this average diameter (since the velocity is assumed to be constant). To assess a general mortality rate of the machine, the mortality rates obtained at the 3 injection points must thus be weighted by the 3 corresponding diameters which are 2.475 m for the inside, 3.487 m for the middle, and 4.500 m for the outside.



Given that the deferred mortality of the test batches linked to the transiting through the VLH has been considered as negligible, the general mortality rate of the machine (Tmg VLH) has been assessed from the corrected immediate mortality rates obtained at the 3 injection points, according to the following formula.

Tmg VLH = (1.0 x 2.475 + 1.4 x 3.487 + 5.5 x 4.500) / (2.475 + 3.487 + 4.500) = 3.1%

Thus calculated, the general mortality rate of the VLH for smolts is estimated at 3.1%.



9.3. Nature of the observed injuries

Mechanical shocks are the main mortality cause in Kaplan-type turbines (LARINIER and DARTIGUELONGUE, 1989; FRANKE et al., 1997). The injuries visually observed on the different smolts used along the 3 tests were of 3 major different types: severing of individuals, bruises, or abrasion/scaling.

Severing

The different observed severings of individuals were all immediately deadly.

Bruises

Breaking of vertebral column Cut behind the left pectoral fin Bruise behind the head

The different bruises visually observed (no autopsy of the general cavity and of the organs) were as a large majority immediately deadly (breaking of the vertebral column, blow behind the head), or deadly after a few minutes or a few hours of housing of the individuals (cuts, bleeding).



Severe abrasion/scaling

The origin of the different observed abrasion/scaling may be imputed either to the transiting through the VLH, or to the fish recovery device (by compression of the fish in the net, for example), although this type of injury has not been observed in the “control” batch. Such an abrasion/scaling was not always deadly. However, as recommended by KOSTECKI and KYNARD (1982), it has been considered that a severe abrasion/scaling was likely to weaken the individuals (in particular, disturbance of the osmoregulation) and to thus jeopardize the success of their migration.

9.4. Other species captured during the tests

During the tests, 5 common trouts (Salmo trutta L.) and 1 non-indigenous crayfish (“signal” crayfish – Pacifastacus leniusculus, Dana 1852) have been caught in the recovery device. The trouts were in apparent good health and have immediately been put back into the water.



10. Discussion

Origin, smoltification state of the used individuals, and recapture rate The 1,218 smolts used in the tests came from a fish farm, since this species is naturally absent from the Tarn river upstream of Albi (natural impassable barrier of the Saut de Sabo). Given the injection device designed to inject the fish as close to the runner as possible, it can be reasonably thought that a possible behavior difference between fish farm smolts and wild smolts would anyway have had little incidence upon the mortality rates assessed in this study.

It has been chosen to carry out the tests at the very beginning of the smoltification period so that the used Atlantic salmon juveniles would not be too fragile (as had been the case for the April 2007 pre-tests). Hence, most of the individuals exhibited signs of a starting smoltification (color change, loss of a few scales, increased agitation), but their general health state was very satisfactory.

On the other hand, the tendency of certain individuals to migrate downstream was not very strong. This was not disturbing in the first place since the injection system would force them to swim downstream through the VLH. However, from 4 to 5 individuals (number visually estimated in a very clear water) have been seen swimming about in the area between the turbine and the entrance of the net, despite the high velocities and the strong turbulences this area and in spite of the “flushings” performed between each test with the VLH at full power and the raised net. The recapture rates of the different batches have never been complete, although the turbine discharge has been totally filtered. The fact for a few individuals from one batch to have mingled with those of the next injected batch cannot be excluded, this however having a limited effect (<0.1%) on the calculated mortality rates, given the relatively large number of 300 injected individuals per batch.

Turbine running conditions during the tests The preferential downstream migration period of smolts in the southern part of Europe is spring, generally from March to May (BAGLINIERE, 1976 ; BŒUF, 1994 ; CHANSEAU et al., 1999). It occurs in essentially nocturnal steps, following flow rate increases. During this period of the year, the Tarn flow rate is generally greater than the maximum discharge of the Troussy mill. Thus, we have chosen to carry out the tests with the most current turbine operating rate in such strong flow conditions at the preferential smolt migration period, that is, at full opening and full power. The results obtained in the present study are thus as a whole only valid for a full opening turbine operating rate.

Mortality rates The mortality rates encountered for salmonid juveniles in the case of Kaplan-type turbines, which are very variable according to the runner characteristics, to the turbine operating rate, to the head height, as well as to the species and the size of the concerned fish, generally range between 5% (for turbines of large diameters installed on low heads) and approximately 20% (LARINIER and TRAVADE, 2002).

For very low heads like in Millau, it is difficult to compare conventional Kaplan turbines installed on such sites and having undergone seaward-migrating smolt mortality tests with the VLH, especially due to an equivalent or greater size together with a much higher turbine discharge (LARINIER, pers. comm.). Hence, to compare the mortality rates obtained with the VLH to those which would have been obtained with a conventional Kaplan turbine for a same



turbine discharge, it has been necessary to size a “Kaplan turbine equivalent” of the VLH installed in Millau. Considering the characteristics of the turbines provided by most manufacturers and the installations already performed on quite similar sites, the equivalent Kaplan turbine could have the following main characteristics, for a maximum 20-m3/s discharge and a 2.5-m head height: runner diameter close to 2.4 m; runner rotation speed of approximately 115 cpm; runner comprising 4 blades.

Turbine characteristics Site

Head

height Type Opening Diameter Rotation speed

Number of blades

Estimated

mortality rate

Conven-tional

Kaplan 100% 2.4 m 115 cpm 4 from 5 to 7%Tarn in

Millau 2.5 m

VLH 100% 4.5 m 40 cpm 8 3.1%

With such a sizing, the mortality rate obtained on this equivalent conventional Kaplan turbine would be from 5 to 7% for smolts, using the predictive models provided by LARINIER and DARTIGUELONGUE (1989) and recently modified to take into account results obtained in more recent experimentations (LARINIER, pers. comm.), that is, from 1.6 to 2.3 times greater than that obtained with the VLH currently installed in Millau.

Calculation mode of the general mortality rate of the VLH The general mortality rate for the VLH has been estimated based on the corrected immediate mortality rate, without taking into account the deferred mortality linked to the transiting through the VLH, since it has been considered as negligible. Anyway, even taking this deferred mortality into account, the overestimated mortality rate thus calculated would remain smaller than that obtained with the equivalent conventional Kaplan turbine (4.7% versus from 5 to 7%).

Smolt injection device and points Studies of the mortality generated by the passing of fish through a hydroelectric turbine can be divided in two large groups: those capturing at the turbine outlet the fish having “naturally” swam down through the machine and those using fish directly injected into the water chamber of the turbine (GIBSON and MYERS, 2002). The studies of the first group are not biased as to the fish injection. However, they do not enable knowing how the fish behave when reaching the turbine and at which level of the blade they cross it.

The Millau experimentation belongs to the second group, given the natural absence of salmon on the Tarn upstream of Albi. The injection device used in Millau, the principle of which is inspired from tests carried out in Québec on the Saint-Laurent river (DESROCHERS, 1995; THERRIEN, 1999), has been designed to directly inject the fish at the level of the turbine guide blades, to force them to transit through the machine. Even if this can introduce a bias, the possibility of varying the injection point has allowed us to show, as for the tests carried out on silver eels (LAGARRIGUE et al., 2008), that the mortality rate was low close to the hub, intermediary at mid-blade, and maximum at the runner periphery (4 times greater than that obtained at mid-blade), and to thus locate the machine area which seems to be most problematic for the downstream migration of smolts as well as of eels.



Type of observed injuries and location of the fish severing point Mechanical shocks are the main mortality cause in Kaplan-type turbines (LARINIER and DARTIGUELONGUE, 1989; FRANKE et al., 1997). Further, in the VLH, risks of abrupt acceleration or deceleration are limited and pressure variations are very small. The bruises observed on the smolts of the test batches and absent from the smolts of the “control” batch can thus be imputed to shocks against the fixed or mobile portions of the turbine, despite small runner rotation speeds (on the order of 40 cpm), water flow velocities inside of the runner < 2 m/s and the very rounded profile of the leading edges of the blades. It seems however more difficult to incriminate the VLH for severe abrasion/scaling which can be rather imputed to the fish recovery device (by compression of the smolts in the net, for example). No similar injuries have been observed on the eels during the tests carried out in December 2007 in Millau (LAGARRIGUE et al., 2008) but this species is considered “more robust” and has no scales.

However, as in the observations made during the tests on silver eels (LAGARRIGUE et al., 2008), the mortality increase from the hub to the blade tip, already shown on Kaplan turbines (see CADA’s synthesis, 2001), and the nature and the clearness of the observed severings of individuals, lead us to think that such severings cannot have been caused by a shock with the blades. However, there exists a possible severing area between the cylindrical discharge ring at the end of the blades and the blade tips (the section of which can be considered as a right angle triangle with a side of approximately 5x15 centimeters). Indeed, according to the VLH structure, this is the only place at the machine periphery with a sufficient space for a smolt or an eel, even of large diameter, to get stuck and where such a clean severing of the individuals can be induced.

Thus, on the Millau VLH, the gradual mortality increase observed from the hub to the runner periphery would be linked to the probability for the fish to pass at the periphery, which is all the smaller as the individual is injected close to the hub.

Possible improvement direction for the “fish-friendly” performances of the VLH Many elements converge towards a mortality which seems to be essentially linked to the presence of a severing point between the discharge ring and the blade tip. In its current version, the cylindrical discharge ring of the VLH at the end of the blades leaves a sufficient space for a smolt or an eel, even of large size, to get stuck and be severed.

It is technically possible, for new projects, to modify the hydraulic contour at the blade tip towards a spherical profile almost suppressing this space and thus expect to significantly decrease the mortality rate generated by the VLH.

Location of the potential severing area between the blade tip and the discharge ring



A so-called MGR (Minimum Gap Runner) Kaplan turbine prototype, supposed to be “fish-friendly”, has been installed in 1999 on the Columbia River (Bonneville Dam First Powerhouse installation). Its main characteristics especially are the use of spherical profiles at the hub and at the discharge ring enabling reducing to a minimum the gaps between blade and hub and between blade tip and discharge ring. Even though the global mortality of the MGR turbine is not significantly different from that of the conventional Kaplan turbine tested in parallel, the mortality at the blade tips of Chinook salmon juveniles has been reduced by 3% with the MGR with respect to the mortality at the blade tips of the conventional Kaplan turbine (NORMANDEAU et al., 2000).

Comparison between (a) a conventional Kaplan turbine and (b) the MGR turbine

(modified according to ODEH, 1999 in CADA, 2001).

Current discharge ring and potential severing area at

the VLH blade tip Technically-feasible spherical discharge ring at the

blade end to reduce the potential severing space



11. Conclusions - Prospects

The global mortality rate of Atlantic salmon smolts estimated at 3.1% on the Millau VLH operating at full opening and full power makes it less penalizing than conventional Kaplan turbines towards the seaward migration of juveniles of this species. For a similar turbine discharge, the mortality rate obtained with the VLH thus is from 1.6 to 2.3 times less than with an “equivalent” Kaplan turbine. Further, this global mortality rate is assessed on individuals transiting through the turbine. Now, the proportion between smolts transiting through the turbine and smolts following other pathways (dams, spillways…) may be very variable according to sites, especially according to the design discharge of the power station and over the years, on a same site, according to the hydrology during migration peaks.

Such relatively moderate mortality rates for Atlantic salmon smolts should be compared with those observed for silver eels with a global mortality rate of large adult eels which has been estimated at 7.7% on the Millau VLH operating at full opening and full power, which made it also less penalizing than a conventional Kaplan turbine (for a similar discharge rate, the mortality rate obtained with the VLH is at minimum 2.5 less than with an “equivalent” conventional Kaplan turbine – LAGARRIGUE et al., 2008).

Such mortality rates generated by the VLH, be it for Atlantic salmon smolts or large adult silver eels, may be considered as rather low as compared to those obtained in the transiting through conventional Kaplan turbines. They however remain non-negligible, especially when thinking in terms of cumulative impact on an axis comprising a series of hydroelectric works between ongrowing areas of salmon juveniles and adult eels and the estuary. Hence, the significant prospects of improvement for the “fish-friendliness” of the VLH are promising, since the origin of the mortalities has been pinpointed. They must thus be considered thoroughly for future harnessing projects to limit the cumulative impact on the concerned migration axes.



12. Bibliography

BAGLINIERE J.L., 1976. Etude des populations de Saumon atlantique (Salmo salar L.) en Bretagne-Basse-Normandie. 1 – Caractéristiques des smolts de la rivière Ellé. Ann. Hydrobiol., 7, 141-158. BELL C. E. and KYNARD B., 1985. Mortality of adult shad passing through a 17 MW Kaplan turbine at a low head hydroelectric dam. North Am. J. Fish. Management, 5, 33-38. BŒUF G., 1994. La phase de préadaptation à la vie en mer : la smoltification. In Le Saumon atlantique, IFREMER (Ed.), 47-63. CADA G.F., 2001. The development of advanced hydroelectric turbines to improve fish passage survival. Fisheries, 26(9) : 14-23. CHANSEAU M., LARINIER M. et TRAVADE F., 1999. Efficacité d’un exutoire de dévalaison pour les smolts de saumon atlantique (Salmo salar L.) et comportement des poissons au niveau de l’aménagement hydroélectrique de Bedous sur le Gave d’Aspe étudiés par la technique de marquage-recapture et par radiotélémétrie. Bull. Fr. Pêche Piscic., 353/354, 99-120. COURRET D. et LARINIER M., 2007. Guide pour la conception de prises d’eau ichtyocompatibles pour les petites centrales hydroélectriques. Rapport d’avancement GHAAPPE RA.07.02-V1 de Novembre 2007, 46 p. + annexes. DARTIGUELONGUE J. et LARINIER M., 1987. Mise au point d’un protocole expérimental pour l’évaluation des dommages subis par les juvéniles lors de leur transit à travers des turbines. Rapport CEMAGREF / DPN, Convention DPN n°85/8, 20 p + annexes. DESROCHERS D., 1995. Suivi de la migration de l’anguille d’Amérique (Anguilla rostrata) au complexe Beauharnois. Rapport Milieu et Associés pour Hydro-Québec, 107 p. FRANKE G. F., WEBB D. R., FISHER R. K. Jr., MATHUR D., HOPPING P. N., MARCH P. A., HEADRICK M. R., LACZO I. T., VENTIKOS Y. and SOTIROPOULOS F., 1997. Development of environmentally advanced hydropower turbine system design concepts. Idaho National Engineering and Environmental Laboratory, 161 p. + annexes. GIBSON A. J. F. and MYERS R. A., 2002. A logistic regression model for estimating turbine mortality at hydroelectric generating stations. Trans. Am. Fish. Soc., 131, 623-633. GLOSS S. P. and WALH J. R., 1983. Mortality of juvenile salmonids passing through Ossberger crossflow turbines at small-scale hydroelectric sites. Trans. Am. Fish. Soc., 112, 194-200. KOSTECKI P. and KYNARD B., 1982. Potential effects of scale-loss on mortality of Atlantic Salmon smolts and juvenile Clupeids. In Potential effect of Kaplan, Ossberger and Bulb turbines on anadromous fishes of the Northeast United States, Final technical report,



FWS/OBS-82/62, 99-114, Fish an Wildlife Service, U. S. Dept. of the Int., Newton Corner, Massachusetts. KYNARD B., TAYLOR R., BELL C. and STIER D., 1982. Potential effects of Kaplan turbines on Atlantic Salmon smolts, American shad and Blueback herring. In Potential effect of Kaplan, Ossberger and Bulb turbines on anadromous fishes of the Northeast United States, Final technical report, FWS/OBS-82/62, 5-50, Fish and Wildlife Service, U. S. Dept. of the Int., Newton Corner, Massachusetts. LAGARRIGUE T., VOEGTLE B. et LASCAUX J. M., 2008. Tests d’évaluation des dommages subis par les juvéniles de salmonidés et les anguilles argentées en dévalaison lors de leur transit à travers le groupe turbogénérateur VLH installé sur le Tarn à Millau – Tests de décembre 2007 sur des anguilles argentées. Rapport E.CO.G.E.A. pour F.M.F., 25 p. + annexes. LAGARRIGUE et LASCAUX, 2007. Tests d’évaluation des dommages subis par les juvéniles de salmonidés et les anguilles argentées en dévalaison lors de leur transit à travers le groupe turbogénérateur VLH – Tests préliminaires d’avril 2007 avec des smolts de saumon atlantique. Rapport E.CO.G.E.A. pour F.M.F., 14 p. + annexes. LARINIER M. et DARTIGUELONGUE J., 1989. La circulation des poissons migrateurs : le transit à travers les turbines des installations hydroélectriques. Bull. Fr. Pêche Piscic., Numéro spécial 312-313. LARINIER M. et TRAVADE F., 2002. Downstream migration: problems and facilities. Bull. Fr. Pêche Piscic., 364 (suppl.), 181-207. MONTEN E., 1985. Fish and turbines. Fish injuries during passage through power station turbines. Vattenfall, Stockholm, 111 p. MONTREAL ENGINEERING COMPANY, Ltd, 1981. Fish mortality as a function of the hydraulic properties of turbines. Canadian Electrical Association, Research and Development, report G 144, 75 p. MONTREAL ENGINEERING COMPANY, Ltd, 1982. Fish mortality in Francis turbines. Canadian Electrical Association, Research and Development, report G 261, 131 p. NORMANDEAU ASSOCIATES Inc., J.R. SKALSKI AND MID-COLUMBIA CONSULTING Inc., 2000. Direct survival and condition of juvenile Chinook Salmon passed through an existing and new Minimum Gap Runner turbines at Bonneville Dam First Powerhouse, Columbia River. Report to U.S. Army Corps of Engineers, Portland District, Portland, Oregon. THERRIEN J., 1999. Evaluation du taux de survie d’anguilles adultes passant par la centrale hydroélectrique de Saint-Lambert en 1998. Rapport du Groupe-Conseil Génivar inc. pour Hydraska (St-Lambert) inc., 24 p. + annexes.


E.CO.G.E.A. pour F.M.F., Avril 2008.

APPENDIXES



Short presentation of the VLH concept



Implantation of the VLH on the Millau site



Fish recovery device

• Net supporting frame,

• Net,

• Floating fish box.

Tests for evaluating the injuries suffered by downstream ... · 4.1. The Tarn River 4.1.1. General...

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