WASSERBER LIN 2006Internationale Fachrnesseund Kongress

( Durchgngigkeit von Gew i ssernfür die a quatische Faunafree Passage for Aquatic Faunain Rivers and other Water Bodies

April 2006

Internationales DWA-Symposiumzur Wasserwirtschaft

International DWA Symposiumon Water Resources Management

3.- 7. April 2006

Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e.V.German Association for Water, Wastewater and Waste

Durchgângigkeit von Gewâssern für die aquatische FaunaFree Passage for Aquatic Fauna in Rivers and other Water Bodies

Die Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e.V., DWA, ist in DeutschlandSprecher für aile übergreifenden Wasserfragen und setzt sich intensiv für die Entwicklung einer sicherenund nachhaltigen Wasserwirtschaft ein. Als politisch und wirtschaftlich unabhângige Organisation arbeitetsie fachlich auf den Gebieten Wasserwirtschaft, Abwasser, Abfall und Bodenschutz.

In Europa ist die DWA die mitgliederstàrkste Vereinigung auf diesem Gebiet und nimmt durch ihre fachlicheKompetenz bezüglich Normung, Beruflicher Bildung und Information der Offentlichkeit eine besondereStellung ein. Die rund 14.000 Mitglieder reprâsentieren die Fachleute und Führungskrâfte aus Kommunen,Hochschulen, Ingenieurbüros, Behôrden und Unternehmen.

Der Schwerpunkt ihrer Tâtigkeiten liegt auf der Erarbeitung und -Aktualisierung eines einheitlichentechnischen Regelwerkes sowie der Mitarbeit bei der Aufstellung fachspezifischer Normen auf nationalerund internationaler Ebene. Hierzu geh&ren nicht nur die technisch-wissenschaftlichen Themen, sondernauch die wirtschaftlichen und rechtlichen Belange des Umwelt- und Gewâsserschutzes.

The DWA - German Association for Water , Wastewater and Waste - is in Germany spokesman for allcomprehensive water queries and is intensively committed to the development and distribution of a secureand sustainable water supply . It works as a politically an ecônomically independent organisationprofessionally in the fields of water management , sewage , waste and soit protection.

DWA is in Europe the association with the largest number of members within this field and therefore takesup a special position . This is because it provides professional competence regarding standardisation,professional training and information towards the public . Approximately 14.000 members represent theexperts and executives from communes , universities , engineering offices, authorities and enterprises.

The main emphasis of its activities is on the acquirement and update of a uniform technical set of rules andstandards -as well as the cooperation on the list of technical norms on a national and international level. Inthis connection not only are the technical scientific topics involved , but also the economic and legalinterests of the environment and water pollution forms a part.

Impressum / Imprint

Herausgeber und VertriebPublishing and Distributions:DWA Deutsche Vereinigung fürWasserwirtschaft, Abwasser und Abfall e. V.Theodor-Heuss-Allee 1753773 Hennef, Deutschland/GermanyTel.: +49 2242 872-0Fax: +49 2242 872-100E-Mail: kundenzentrum@dwa.deInternet: www.dwa.de

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ISBN:I S B N-10: 3-939057-19-3ISBN-13: 978-3-939057-19-2

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© DWA Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V., Hennef 2006© DWA German Association for Water, Wastewater and Waste, Hennef 2006

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2 April 2006 DWA

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Durchgângigkeit von Gewâssern für die aquatische Fauna

Free Passage for Aquatic Fauna in Rivers and other Water Bodies

French experience in upstream migration facilities

Erfahrungen mit Fischaufstiegsanlagen aus Frankreich

Michel Larinier, Institut de Mécanique des Fluides, Toulouse, France

François Travade, Electricité de France - Etudes et Recherches,Chatou CEDEX,France

Abstract

Many fish passes have been built to apply the 1984 legislation on freshwater fishing and management offish-breeding resources, with the target migrating species being above ail diadromous species. The articlefirst considers the way in which the swimming capacities of migratory species are taken into account whendesigning fish passes. A review is then made of experience acquired with different types of fish pass: poolfish passes, natural bypass channels, fish lifts and locks, specific passes for eels. The concept of efficiencyof fish passes will be illustrated with a few examples, with an emphasis on the attraction of fish passes andthe maintenance issues . The authors also discuss some of the techniques used for inspecting andevaluating fish passes, namely video control stations and radio telemetry.

Keywords: upstream migration, fish pass, radio tracking, monitoring.

1 Introduction

The first plans for restoration or enhancement of diadromous fish species were undertaken between 1975 and1980 and new legislation on freshwater fishing and management of fish-breeding resources was passed in1984. This led to an intense fish pass construction programme, then a few years later to the awareness thatdownstream migration had to be taken into account for hydroelectric plants. The European Water FrameworkDirective confirmed the increasing awareness of the importance of ecological continuity for ail species in riversand streams. This paper only deais with upstream migration since the downstream aspect is being dealt withby a twin paper written by the same authors (for presentation in this saine Symposium). This paper deais withthe experience acquired, particularly over the last ten years, in other words since the Vienna Symposium onFish Migration and Fish bypass Channels held in September 1996 (Larinier, 1998 ; Travade et al., 1998). Thebreakthroughs made are due mostly to monitoring of existing fish passes. Some points, in particular thecriteria used for designing passing facilities will only be dealt with very briefly in what follows, given that theyare very similar to or even identical to those used in Germany (DVWK, 2002 ; Larinier et al., 2002) and thatthey are being covered by specific papers during this Symposium.

2 RegulationsMost of the fish pass facilities were built to apply the law of 1984. This Iaw (Environnent Code, ArticleL 432-6) requires that ail obstructions in rivers or parts thereof, in the list specified by decree, must includefacilities to guarantee the passage of migratory fish. The owner of the obstruction is obliged to ensure theoperation and maintenance of these facilities. Existing obstructions are required to conform to theprovisions of this Article within five years following publication of the Ilst of migratory species by river basinor sub-basin, as specified by the responsible Minister, without compensation.

At new obstructions, or during the relicensing of existing hydropower facilities, the authorities may requirethat fish passes be built, even on rivers which are not classified in terms of the law as `migratory'. Thus fishpasses can be built for resident species on ail new or. relicensed obstructions.

In our opinion, the very important part of the regulations is that not only are operators obliged to provide themeans (by building a fish pass) but they are also under the obligation to ensure results, in other words that

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Durchgângigkeit von Gew âssern für die aquatische FaunaFree Passage for Aquatic Fauna in Rivers and other Water Bodies

the fish passes built must be efficient. This obligation to achieve a result was a major element in theprogress made in this field. It was also the reason why a significant fish monitoring programme was set upto assess the efficiency of fish passes.

3 Migrating species and obstacles

In keeping with regulatory obligations, fish passes were initially designed for a limited number of targetspecies: diadromous salmon species (Salmo salar), sea-run brown trout (Salmo trutta), sea lamprey(Petromyzon marinus), allis shad (Alosa alosa) and. European eel (Anguilla anguilla). The only riverinespecies considered as 'migratory species' in the law are brown trout (Salmo trutta), Northern pike (Esoxlucius) and European grayling (Thymallus tymallus).

Since the promulgation of the European Framework Water Directive, an effort is being made to take intoaccount all species in a more determined way, but difficulties have been encountered for some rivers in thatthis means significantly modifying design criteria and usual technical choices.

No complete inventory of fish passes has yet been made but more than 700 fish passes have been eitherimproved or built over the last twenty years. Most of these facilities are on the Atlantic coastline, small coastalrivers in Normandy and Brittany, or on the river basins of the Loire, the Dordogne, the Garonne and Pyreneanrivers and these concem all diadromous species, as well as trout for the upper part of the basins. In theRhône basin, which has no migrating salmonids, fish passes have been built for shad and lamprey on thelower part of the basin and for trout on the upstream part. During renovation, or rebuilding of navigationstructures on the Seine and its main tributaries (the Oise, Marne and Yonne rivers), a significant fish passconstruction programme was undertaken a few years ago, with a view to catering for all riverine species.

The sizes of the rivers on which fish passes have been built vary from streams with a flow of a few hundredIls to our major rivers (Garonne, Loire, Seine, Rhone, Rhine) whose annual flow discharges are somewherebetween 300 and 1900 m3/s.

The types of obstacles vary greatly: old mill weirs, hydroelectric plants, navigation dams, dams for tourism,stabilisation weirs, intake weirs for thermal power plants...

Most of the obstacles have been equipped with fish passes while some old and low weirs have beenremoved. Three dams, 6 m to 15 m high (Maisons-Rouge on the Vienne, Saint-Etienne-du-Vigan on theAllier and Kernansquillec on the Leguer) were decommissioned when their concessions or authorisations touse the hydroelectric power expired.

4 Swimming capacities and fish passesThe design criteria for fish passes are closely related to the migratory behaviour and swimming capacitiesof the target species. There is a great deal of literature on this field, most of which comes from experimentsundertaken with controlled environments while some, but not very many, corne from observations in naturalenvironments.

The main difficulty consists in transforming the data on swimming capacities - with all of the uncertaintyand dispersion involved - into criteria for the passability of an obstacle or into acceptable flow velocities fora fish pass.

It is practically impossible to limit the maximum flow velocities at values much lower than 1.30-1.50 m/s whichcorresponds to the burst speed of small species. This means that the small species must either avoidmaximum velocity zones by using wakes behind obstacles or bottom roughness. In any event, the smallspecies have to find resting areas which must be very close to each other whereas larger species will be ableto cover several tens of metres in the same flow conditions without any difficulty.

Moreover, when the spatio-temporal variations in flow velocities are great (for very turbulent flows or eddiesfor instance), more energy will be needed for the fish to move a certain distance than that required to coverthe same distance in a more regular flow with parallel stream lines having the same velocity and this can be

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Durchgângigkeit von Gewâssern für die aquatische Fauna

Free Passage for Aquatic Fauna in Rivers and other Water Bodies

particuiarly critical in circumstances in which the maximum velocities of the flow cornes close to the burstspeed of the fish. This is what has been observed in Denil fish passes for small fish: even though the flowvelocities are not that great, the fish find it somewhat difficult to progress becausé of the three-dimensionalflow patterns.

Until fairly recently, there was no way of measuring this turbulence. A good indicator of the level of agitationand aeration in basins, but a very empirical method, is volumetric dissipated power (Larinier, 1983, 1990).The use of this criterion for designing pool fish passes has now become widespread. This volumetricdissipated power is identical to the 'unit stream power' used in fluvial geomorphology and river mechanics,which is a good indicator of the capacity of flow to transport sediment (Yang, 1984 ; 1996). The values ofthe dissipated power may vary from a few watts/m3 in the lower part of the watercourse to values of theorder of 500 watts/m3 locally in the upper trout zone.

The effect of turbulence on fish behaviour was recently investigated in particular with the development oftechnology such as Acoustic Doppler Velocimetry, which can be used both in laboratories and in situ (Odehet al., 2000 and Hotchkiss, 2002). While it is obvious that turbulence is an important factor, no experimentalinvestigations have yet clearly determined the most significant parameters to be taken into account and afortiori the threshold values or critical values for these parameters. The turbulent kinetic energy (TKE)seems to be the 'most suitable parameter for quantifying the extent of fluctuations to which an aquaticorganism is subjected as it natura*lly integrates the three components of instantaneous velocity.Experiments are underway in France to characterise flow in fish passes (vertical slot and natural-like fishpasses) with -respect to turbulence.

5 Fish passes

5.1 Pool fish passes and pre-barragesThe most frequently used type of fish pass in France is the pool fish pass. The difference in level betweentwo successive pools, which is a function of the migrating species, is most often between 20 and 30 cm.Such differences allow most species to pass. When the target species are smaller then the difference inlevel can be reduced (to 15 cm for instance for Zingel Asper, percid [GOMES et al., 2005]). The volume ofthe pools is determined from the maximum volumetric dissipated power which the fish can tolerate, of theorder of 100 to more than 200 watts/m3 depending on target species. For salmonid passes , a volumetricdissipated power of the order of 200 watts/m3 is recommended for passes with many pools. Much greatervalues may be taken for a limited number of pools (more than 300 watts/m3). For shad and cyprinid passes,lower values are recommended (less than 150 watts/m3). In Australia (Malien Cooper, personalcommunication, 2003), recommended even lower values (50-100 watts/m3) for very small species of a fewcm in length.

The length of the pools can vary from less than 1.50 m for a pass designed for a low flow discharge to morethan 5 m for a salmon pass designed for a flow discharge of more than 1 m3/s.

Vertical slot fish passes have the great advantage of operating correctly without any regulating device - bytolerating significant variations in upstream and downstream water levels - and of allowing fish to pass fromthe bottom up to the surface of the pool. Experience has shown that when a pool pass has been correctlydesigned (in terms of drops, level of turbulence and flow pattern in the pools), it is net very selective andcan be crossed by most species likely to want to do se.

The main problem for some species is the significant time spent in very large pools : small species tend to'get'lost' and to remain trapped in large recirculation eddies. A good solution is to reduce the size of pools,if possible, or to find ways of reducing the size of these recirculation eddies.

A study of vertical slot fish passes is underway to characterise flow in terms of speed, turbulence, flowpatterns and to see which devices may be used in pools to help guide small species. It is already clear thatthe introduction of rough obstacles on the bottom helps small species to pass through but this only helpsbenthic species.

It is difficult to optimise the design of a fish pass by taking into account the requirements or rather thepreferences of ail species: for the large species, it would be becter to limit the number of drops by adopting

1

1

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Durchgângigkeit von Gewâssern für die aquatische FaunaFree Passage for Aquatic Fau na in Rivers and other Water Bodies

fairly wide fish passages and pools with maximum flow velocities of the order of 2.2 m/s to 2.50 m/s whichare still within the range of sustained speeds for fish. For the smaller species it would be preferable toreduce both drops and volumetric dissipated power as much as possible and especially the widths of fishpassages as well as the sizes of pools.

Several hundred pool fish passes have been built over the last twenty years in France. The cost of the structureis above all determined by the flow discharge of the structure and the drop to be passed. The cost may varyfrom less than 20 K€ (fora small fish pass on a low dam) to more than 1,500 K€ (fora multispecies pass on alarge river), for an average of 120 K€ per metre of head drop and m3/s of flow. Exceptionally the cost mayamount to 9 million € as for the large fish passes recently built on the Rhine.

Pre-barrages are often an efficient and inexpensive solution to enable fish to clear fairly low obstacles..They are made of several walls or weirs creating, downstream of the obstacle, large pools which break upthe drop to be cleared (drops of 0.40 m to 0.60 m). The configuration of the weirs and drops between poolsdepends on the target species: for saimonids, plunging flow is acceptable and the walls between pools canbe vertical whereas for most other species it is better to progressively dissipate energy and reducevelocities on rough ramps to enable the fish to moue through by swimming. The average cost is 70 K€ permetre of head drop and m3/s of flow.

Figure 1: Vertical siot fish pass (Seine river) Figure 2 : Pre-barrage with roughenedramp (Loire river)

5.2 Denil fish passesDenil fish passes are relatively selective and are only used for species which have sufficient swimmingspeed and endurance. They are used for large fish and in particular salmon, sea trout and marine lampreyfor which this type of pass seems to be very efficient, much more than a pool fish pass.

Denil fish passes are particularly suitable for small watercourses in which the flow necessary for the fishpass is only a few hundreds of Ils. More than a hundred passes of this type have been installed over thelast fifteen years, mainly in rivers on the Brittany and Normandy toast. The average cost is 50 K€, for anaverage of 75 K€ per metre of head drop and m3/s of flow.

They are not very widespread at the moment to the extent that the idea is to cater for most species, inparticular small species with reduced swimming capacities.

5.3 Locks and liftsA few fish locks were built in France in the years from 1960-1975. With a few rare exceptions, they neverperformed entirely satisfactorily, most often due to a far from optimal design (e.g. holding pool too small andturbulent, poor gate operation, inadequate attraction). The principal limit to this kind of facility is that it is

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Durchg ângigkeit von Gewâssern für die aquatische FaunaFree Passage for Aquatic Fauna in Rivers . and other Water Bodies

difficuit, if not impossible, to optimise its operating cycle when several species with very different behaviourare concerned. At the current time, the installation of fish locks is no longer envisaged and mechanical liftsare generally preferred.

On the other hand, on some watercourses, the operation of navigation locks has been modified to facilitatefish passage, for instance on the Rhône over the last ten years for shad. To attract the fish into the lock, thefilling sluices are opened while the downstream gates are open which creates a significant attraction flow(of the order of 60 m3/s at the Beaucaire lock and 80 m3/s at the Avignon lock), corresponding to 2.5-5% ofmaximum turbine flow (respectively 2400 m3/s and 1600 m3/s). The efficiency of this device, which wasevaluated by radio-telemetry over three years, is about 40% for a relatively limited number of lock operationcycles (of the order of 100-150 specific lock operation cycles during the migration period) (Roche & Brosse,2005). However, this operation is not compatible with river transport (boats) and the number of 'fish cycles'cannot be increased. In the case of the Rhone, the use of locks appears to be a worthwhile alternative tothe building of specific fish passes on condition that there will be no significant increase in navigation.

In mechanical lifts, thé fish are directly trapped in a tank. At regular intervals, this tank is spilled outupstream. An auxiliary flow, which is used to attract fish and incite them to enter the tank, is injectedupstream of the trap. Installation of lifts is only practicâl for drops greater than 7 to 8 metres. The cost of alift, independently of the drop height, depends on the amount of civil engineering necessary for integrating it.into the structure and the cost of the attraction device. For structures which require relatively litt ►e civilengineering, the costs are about 200 to 300 K€. On major watercourses, the cost may amount to 3.5 M€(e.g. the Golfech fish lift on the Garonne river).

The main disadvantage of fish lifts lies in the higher cost of operation and maintenance. Furthermore, theirefficiency for small species (e.g. young eels) is generally low because sufficiently fine screens cannot beused for operational reasons. Fish lifts have some moving parts which may lead to damage and a few fishmortalities which may be reduced but are difficult to avoid.

Figure 3 : Fish lift at Poutès dam (Allier ) Figure 4: Tuilières fish lift (Dordogne)

5.4 Fish ramps and natural bypass channelsSome rock weirs extending over the whole width of a watercourse are used as fish passes for diadromousspecies, with the ramps slopes being limited to 10% and the drops to 1.50 m. In this case, the acceptableflow discharges per metre of width (from 0.2 to 1.5 m3/s/m) depend on the species. Most of these wereoriginally designed as stabilising weirs whose.slope has been deliberately reduced to make them easier topass through.

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Durchgâng . igkeit von Gewâssern für die aquatische Fauna

Free Passage for Aquatic Fauna in Rivers and other Water Bodies

Natural bypass channels are particularly suitable if the fish pass has to be installed near a dam whichcannot be changed structurally and when there is sufficient space in the bank. The siope for this typé ofstructure generally varies from 2% to 5%, depending on the target species. The major disadvantage of thistype of device. is its overall dimension and the difficulty of taking into account significant variations in theupstream level. The energy is generally dissipated by rows of blocks or weirs créating a series of drops bfvariable height (from 15 to 30 cm). The design critéria (in terms of drops and dissipated power) are.verysimilar to those for pool fish passes. It is better to leave a margin for the acceptable maximum drops, giventhe difficulty of obtaining precise values during construction. If the level of upstream water variessignificantly, a regulatory section has to be installed upstream and the most efficient system generallyrecommended is a section of a vertical slot, pool fish pass.

Figure 5: Natural bypass channels on the Gave de Pau river and on a Rhône tributary(Bras des Arméniers)

The limit conditions for opération of ramps are, in our opinion, not very well defined. Tests were performedtwo years ago to specify the hydraulic conditions (in terms of velocity and turbulence characteristics offlows) depending on the arrangement of the blocks and their concentration and particularly in terms of thetwo basic parameters: the specific flow discharge and the slope. An example is the statistical evolution ofvelocity as well as the turbulent kinetic energy measured in areas of low velocities, which are supposed tobe rest areas, depending on the slope in a ramp made of regularly arranged rocks (Chorda et al., 2004Gomes et al., 2005). Tests on fish behaviour are carried out at the same time in a fluvarium.

6 EeI passesEel migrations have only relatively recently been taken into account in France and the first fish passesadapted for this species were only built about ten years ago. The first passes used consisted exclusively ofbrushes installed on a PVC substrate, brushes with différent characteristics depending on the size andstage of development of the eel. Experiments were conducted between 2000 and 2002 to test more robustsubstrates which were less expensive, consisting of prefabricated moulded concrete slabs with conicallyshaped blocks of different diameters and layout. The advantage of this substrate over conventional brushesis that it can be installed for significant widths on sloping faces of weirs. Tests were conducted at anexpérimental site consisting of channels with variable slopes installed in the Arzal dams on the Vilaine andthe Tuilières dam on the Dordogne to test the effect of flow discharge, siope and the size and arrangementof the blocks. They focused on elver and young eels of a maximum size of 30 to 40 cm (Voegtle & Larinier,2000). The optimum substrate consisted of conical blocks with diameters of approximately 3-4 cm, laterallyspaced at intervals 2 times their diameter and disposed in quincunx.

A counting system based on the adaptation of an existing resistivity counter has been developed. Itconsists of 4 counting tubes installed in parallel upstream of the fish pass at the level of the outlet trap. Theefficiency of the counting device which has been tested for a few years turned out to be significantly highgreater than 95% for small eels varying from 13 cm to more than 40 cm. The counter is capable ofdiscriminating between about ten différent eel size classes.

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Durchgângigkeit von Gewâssern für die aquatische FaunaFree Passage for Aquatic Fauna in Rivers and other Water Bodies

1000

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w 400

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200

HI

0.01 0.03 0.05 0.07

Slope

180

150

.120

90U

60

30

00.01 0.03 0.05 0.07

Slope

Figure 6 : Box and Whisker plots of measured mean velocity V and TKE ( measured in restingareas where V<30 cm/s ) in a roughened ramp.

Efficiency

The legal obligation of owners to achieve a result for the free circulation of fish has Ied to the need tospecify the concept of efficiency for fish passes, and this is often difficult both to define and even more so todemonstrate. Efficiency is expressed both in terms of percentage of the migrating population reaching thebase of an obstacle, then clearing this obstacle and delay in migration, in other words, the time that thepopulation or part of the population takes to pass through the obstacle. Simply counting the fish upstreamof the fish pass is only an indication of the degree of efficiency of the pass if we do not know the size of thepopulation downstream of the pass and likely to move upstream.

The level of efficiency to be achieved for a given site has to be defined in terms of the desired biologicalobjectives. It depends on the species, the number and the location of the obstacle on the migration route.

For salmon, on an obstruction located downstream from spawning areas, the whole of the migratingpopulation should be able to pass through.If, moreover, this watercourse is equipped with many obstacles itwill be necessary to minimise delays to migration caused by these obstacles so that the migrating fish arrive atthe spawning areas in time. If on the other hand, the fish pass is located further upstream of the watercourse,in the middle of the spawning area, then there will be less need for efficiency.

For salmon, an efficiency of 95% to 100% can be obtained on recent well-designed fish passes with delaysof a few hours to a few days (Chanseau et al., 1999 ).

Figure 7: EeI pass on the Durance riverdam

Figure 8 : Resistivity eel counter at Tuilières

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Durchgângigkeit von Gewâssern für die aquatische FaunaFree Passage for Aquatic Fauna in Rivers and other Water Bodies

As an example, the radio-tracking study undertaken on the Gave de Pau from 1995 to 1998 to evaluate thepassability of about thirty obstacles ta the upstream migration of fish showed that:

• 16 structures allowed all of the migrating fish to pass through without significant delays,

• 10 were more serious obstacles to migration in terms of delays or blocking part of the population,

• and especially that five structures, of which several were located on the downstream part of themigration route and of older design, were major obstacles. One of them only allowed 35% (Baigt) of themigrating fish to pass through.

It has been estimated that only 13% of salmon reach the first spawning zones.. We may reasonably hopethat this percentage could increase to 80% over the next few years by improving the passability ofdownstream obstacles, which is now being done.

On hydroelectric facilities fish passes have generally been built (unless the site precluded this) near the powerplant, whereas in the past they were most often built at some distance away, on the dam, where except for high-flow periods, the only flow was the ecological one. This enabled a significant increase in efficiency.

It is difficult to obtain very high rates of efficiency on large rivers in particular due to the lack of attractivenessof facilities related to the limited number of entrances: - experience at Golfech (Garonne) and Mauzac(Dordogne) (with turbined flows of about 400-600 m3/s) showed that a single fish entrance and a single fishpass on a very wide structure or plant can only have a limited efficiency. This is why a second fish passentrance was recently built at Mauzac at the power plant to significantly increase the efficiency. It was notpossible to get.financing for collecting galleries above the turbines for the first large structures built between1985 and 1990 in France. This has now become possible since fish monitoring has shown that it is necessary:on the fish pass installed in 1997 at the Carbonne hydroelectric plant (with a turbine flow of 170 m3/s), threeentrances were installed above the draft tubes of the turbines whereas at the Golfech plant (with a turbine flowof 600 m3/s), ten years earlier, only one entrance could be installed - even though three had been initiallyconsidered during the studies.

The efficiency of any given facility varies according to the migrating species considered. It is generally lowerfor shad and lamprey than it is for salmonids: while figures of 80% or more have been achieved forsalmonids, efficiency is at best only about 50% for shad and lamprey.

Efficiency problems are due not only to a lack of attraction of fish passes (wrong location, number ofentrances and/or insufficient flow discharge), but also to a lack of maintenance of the facilities. Lack ofmaintenance of facilities is a recurring problem in France, that is why the Adour-Garonne Water Agencyrecently introduced a system of bonuses to incite owners to correctly maintain structures.

The obligation on owners to achieve a resuit varies according to the type of watercourse. Local authoritiesare generally much more demânding for a watercourse in which there are diadromous species than for awatercourse in which there are only riverine species. Local authorities may decide that the fish facility is notsufficiently efficient and oblige the owners to introduce any modifications which may be necessary. Thelocal authority generally has to prove that the device is not functioning either through a specific study (ratio-telemetry, counting) or simply through expertise done by the Conseil Supérieur de la Pêche.

Figure 9 : Collecting galleries at Chatellerault (Vienne) and Carbonne (Garonne ) powerplants

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Durchgângigkeit von Gewâssern für die aquatische FaunaFree Passage for Aquatic Fauna in Rivers and other Water Bodies

8 Fish monitoring techniques and techniques for evaluating fish passes

Fish pass structures need to be monitored after being commissioned to ensure that they are efficient; thismonitoring further increases our knowledge of migrating fish populations and their migrations.

Video monitoring

Visual counting is widely practiced in France. It involves passing the fish in front of immersed verticalwindow and has the advantage of enabling most species to be identified without handling them. The videosurveillance technique and image analysis for tracking migrators have been developed over the last tenyears (Cattoen et al., 1999) and now allows for continuous counting throughout the year with limitedpersonnel. Images with fish in them are digitised and stored on a hard disk. Suitable software is used toanalyse the computer files and to generate spreadsheets.

The first control stations were more or less imposed on owners of structures about twenty years ago, oftenwith difficulty, to facilitate evaluation of the fish facilities. The first inspection window was installed in Francein 1985 at the Bergerac dam and was only 40 cm wide, the second was installed the following year on theupstream dam and was 1.50 m wide. Thëre are now about twenty permanent video counting stations usingthis technique in France along the main migration routes (Allier, Dordogne, Garonne, Vilaine, Gave de Pau,Aulne, Touques, Vire...).

By tacit agreement, the French electricity board pays for the operation and the maintenance of monitoringstations on its dams, long enough to demonstrate their efficiency. Once the efficiency has beendemonstrated, if the usefulness of the monitoring station is justified, then its management and maintenanceare taken over by organisations which are responsible for restoration or enhancement of. diadromous fishspecies programmes.

Radio tracking

The radio tracking technique turned out to be very useful for overall evaluation of the efficiency of fishpasses and the accumulated impact of different obstacles on a migration route. It has made it possible toevaluate efficiency in terms of percentage of passage and delays to migration. Among other advantages, ithas enabled scientists to suggest improvements in the operation of fish passes based on objectiveobservations of the behaviour of migrating fish, which may be a determining element when negotiating withthe owner of the dam (Chanseau & Larinier, 2000).

100

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SAPSO (efficiency 74%)

LU

0

1 day 3 days 1 week 2 weeks 3 weeks > 1 month 1 day 3 days 1 week 2 weeks 3 weeks > 1 month

Migration delay

CoEM

Migration delay

1 day 3 days 1 week 2 weeks 3 weeks > 1 monthMigration delay

Figure 10: Fish passes efficiency and migration delays at four dam on the Gave de Pau river.

BAIGTS (efficiency 35,3%) 100 -

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Durchgângigkeit von Gewâssern für die aquatische Fauna

Free Passage for Aquatic Fauna in Rivers and other Water Bodies

An example is the efficiency obtained through radio-tracking on 4 fish passes located on the Gave de Pauin the South-West of France. The Artix and Biron fish passes are recent structures. The Sapso and Baigtsfish passes are older structures. These results helped us convinced the authorities to require that theowners of these two last structures build new and more efficient fish passes, (Chanseau et ai., 1999)

At Baigts, the decision was taken to build a new lift at the only possible location at the site, i.e. on the leftbank opposite the hydroelectric plant. At first, only the lower part of the lift was built and evaluated. Theefficiency of the device was increased by 30-40% to 87%, the median delay in migration caused by theobstacle was reduced from 53 days to 9 days. This improvement was related in particular to the increase inflow discharge at the entrance to the lift from 1 m3/s to 10 m3/s (which should be compared to the averageflow discharges of the river and the turbine flow discharge at the, existing plant, approximately 90 m3/s). Aspecial turbine was installed near the lift entrance to dissipate the energy of the attraction flow required forcorrect operation of the lift (Larinier et al., 2005).

9 Conclusion

At the current time, fish pass techniques are relatively well known, in other words we know both thepossibilities but also the limits of fish passes. As knowledge of the migratory behaviour of different.speciesincreases, it has become clear that it is difficult if not impossible to devise a compromise facility whichmeets the requirements of all species. This is why it is better, when the dam is no longer needed, to removeit and re-establish the longitudinal continuity of a watercourse and thus improve the quality of the habitat.

We still often underestimate or do not sufficiently take into account, in particular during the design phase,maintenance problems for fish passes: a lot of effort is still required in France in this respect.

Another aspect is the accumulated impact of obstacles even those fitted with `efficient' fish passes. Itappears to be difficult and not very conclusive to restore diadromous species into a watercourse with toomany obstacles.

Finally, it should be remembered that progress in the design of fish passes both for upstream and downstreammigration have mostly resulted from in situ experiments and the evaluation of operation of existing structures inrelation to the behaviour of migrating species. The best way of achieving these programmes remains fieldstudies and a multi-disciplinary approach calling on both engineers and biologists.

10 ReferencesCattoen, M., Larinier M. & Thomas N., 1999. Système et logiciels pour la surveillance des passes à

poissons. Bull. Fr. Pêche et Piscic., 353/354, 263-277.

Chanseau M., Croze O., Larinier M., 1999. Impact des aménagements sur la migration anadrome dusaumon atlantique (Salmo salar L.) sur le Gave de Pau (France). Bull. Fr. Pêche et Piscic.,353/354, 211-237.

Chanseau M., Larinier M., 2000. The behaviour of returning adult atlantic salmon (Salmo salar L.) in thevicinity of a hydroelectric plant on the Pau river (France) as determined by radio telemetry. InProceedings of the Third Conference on Fish Telemetry in Europe, Norwich (UK), 20 - 25 juin 1999.257-264.

Chorda J., Larinier M., Thinus Z., 2004. A flume study of steep-slope flows above large-scale roughnesselements and their application to fish passes In the fifth international symposium on Ecohydraulics.Aquatic Habitats : Analysis & Restoration. Madrid 2004, 948 - 952.

DVWK, 2002. Fish passes - design, dimensions and monitoring. FAO, 118 p.

Gomes P., Vighetti S., Larinier M., 2004. Etude pour la conception de passes à poissons adaptées àl'Apron. Rapport GHAAPPE RA05.05, 45 p.

Hotchkiss RH., 2002. Turbulence investigation and reproduction for assisting downstream migratingjuvenile salmonids. Washington State University. Department of Civil and EnvironmentalEngineering Albrook Hydraulics Laboratory. Report DOE/BP-00004633-1, 124 p.

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Durchgângigkeit von Gewâssern für die aquatische FaunaFree Passage for Aquatic Fauna in Rivers and other Water Bodies

Larinier M., 1983. Guide pour la conception des dispositifs de franchissement des barrages par lespoissons migrateurs. Bu!!. Fr. Pêche et Piscic., Special Edition, 39 p.

Larinier M., 1990. Experience in fish passage in France : Fish pass design criteria and downstreammigration problems. In Proceedings of the International. Symposium on Fishways 90. Gifu, Japan.pp.65-74.

Larinier M., 1998. Upstream and downstream fish passage experience in France. In M. Jungwirth, S.Schmutz & S. Weiss (Eds). Fish migration and fish bypasses, Fishing News Book, 127-145.

Larinier M., Travade F., Poecher J.P., 2002. Fishways: biological basis, design criteria and monitoring. Bull.Fr. Pêche et Piscic., 364 suppl., 208 p.

Larinier M., Chanseau M., Bau F., Croze 0., 2003. The use of radio telemetry for optimising fish passdesign. in MT. Spedicato, G. Lembo, G. Marmulla (Eds), Aquatic Telemetry : advances andapplications Proceedings of the Fifth Conference on Fish Telemetry held in Europe. Ustica, Italy, 9-13 June.

Odeh M, Noreika JF., Haro A., Maynard A., Castro-Santos T., Cada GF., 2002; Evaluation of the effects ofturbulence on the behavior of migratory fish. US Department of Energy Bonneville PowerAdministration Division of Fish and Wildlife. Report DOE/BP-00000022-1, 46 p.

Roche P., Brosse L., 2005. Etude par radiopistage de la migration de l'Alose dans le Rhône aval. Rapportintermédiaire n° 2, 56 p.

Travade F., Larinier M., Boyer-Bernard S., Dartiguelongue J., 1998. Performance of four fish passinstallation recently built on two rivers in south-west France. In M. Jungwirth, S. Schmutz & S.Weiss (Eds), Fish migration and fish bypasses, Fishing News Book, 146-170.

Voegtle B., Larinier M., 2000. Etude sur les capacités de franchissement des civelles et anguillettes. Sitehydroélectrique de Tuilières sur la Dordogne (24). Barrage estuarien d'Arzal sur la Vilaine (56).Rapport GHAAPPE RAOO.05, 69 p.+ annexes.

Yang CT, 1984. Unit Stream power Equation for Gravel, J. Hyd. Div. ASCE, 110 (HY 12) :1783-1798..

Yang CT., 1996. Sediment Transport: Theory and Practice. McGraw-Hill, New York.

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