Fish lift performance for upstream fish passage at a large hydroelectric power plant in Touvedo, Portugal

Transcription

1 Fish lift performance for upstream fish passage at a large hydroelectric power plant in Touvedo, Portugal U.M. Cabral and A.L. Marinho E.M. Branco EDP/DCL EDP/DGH Centro de Produção Cávado-Lima Rua Ofélia Diogo da Costa Rua 7, n.º 80, Paradela de Valdozende 39/45 5º , Valdozende , Porto Portugal Portugal J.M. Santos J. Pádua Dept. de Recursos Naturais, Ambiente e Território Labelec Instituto Superior de Agronomia Rua Cidade Goa, 4 Tapada da Ajuda , Sacavém , Lisboa Lisboa Portugal Portugal Different types of fishways have been built worldwide to mitigate the impact of dams on diadromous 1 and potamodromous 2 fish species. Among these, the fish lifts stand as the most cost-effective mitigation measures for high dams for economic and biological reasons. The hydroelectric power plants of EDP Production (EDP Group) are distributed by three large production centres in Portugal: Cávado-Lima, Douro and Tejo-Mondego. The Touvedo dam is one of the 18 power plants in the Cávado-Lima Production Centre (Fig.1). Fig.1) Map of the location: Touvedo dam 1 2 Truly migratory fishes which migrate between the sea and fresh water Truly migratory fishes whose migrations occur wholly within freshwater

2 The Touvedo dam was commissioned on 1993 to modulate the high flows turbined at the Alto Lindoso dam (250 m 3 /s at full load) located 16 km upstream on the Portuguese-Spanish border. Its aim is to temporarily store the flow before returning it to the river with a flow less than 100 m 3 /s. The Touvedo dam has a fish lift with three entrances in the attraction circuit and is located in the tailrace area of the powerhouse (Fig.2). The fish lift main purpose is to maintain the upstream migration of anadromous 3 fish and local potamodromous fish fauna. Although the migration of the former, particularly shad and salmon, has been studied in detail, much less information exists on the migratory ecology of potamodromous species. Their ability to use fish lifts as well as their behaviour when facing the attraction entrances is virtually unknown, yet these species are the predominant group of migratory fish encountered in Iberian rivers. Fig.2) Fish lift in Touvedo three dimensional schemes The present study is part of a rehabilitation project with the goal of improving the longitudinal connectivity for eels and potamodromous cyprinids. It examines fish passage through the Touvedo fish lift over an annual cycle in order to: i) provide information on both seasonal and daily fish passage patterns, ii) identify the effect of environmental variables on the daily number of fish migrating through the facility and iii) evaluate the efficacy of the fish lift for migratory species. Simultaneously, hydraulic characterization of the entrance collection system was implemented through an Acoustic Dopler Velocimeter (ADV) in order to assess species ability to overcome existing velocities at the entrance and in the circuit. From August 2011 to July 2012, the fish lift was continuously monitored with an automatic videorecording system in combination with monthly electrofishing samplings undertaken in a 200-m river segment immediately below the dam. A total of 3443 fish from 5 species were transferred by the lift (Fig.3). Cyprinids were the dominant group collected, and the northern straight-mouth nase Pseudochondrostoma duriense (54.6%) the most abundant species, followed by the European eel Anguilla Anguilla (35.2%). Both these species account for almost 90% of the total of movements. Iberian barbel Luciobarbus bocagei (7.7%) and brown trout Salmo trutta fario (2.5%) accounted for 10.2% of the fish movements, whereas the anadromous sea lamprey Petromyzon marinus was rarely observed. 3 Diadromous fishes which spend most of their lives in the sea and migrate to fresh water to breed

3 Fig 3) Relative abundances of species transferred by the lift (Aug Aug 2012) Almost all movements of nase and eel occurred in the summer and in the beginning of autumn, representing 93.0% and 98.4% of the total species movement, respectively. Barbel movements occurred throughout the year but with greater incidence on the spring and autumn, representing 41.2% and 25.9% of the total movements. Similar to barbel, trout movements were relatively constant across the studied period, increasing in the autumn and early winter with 46.4% of movements observed in this period. Only two lamprey individuals used the fish lift, both observed in June after the spawning season. Species movements were predominantly associated with reproduction, refuges and also feeding purposes, particularly the eel. All species seemed to use the fish lift independently of the time of day, as no significant preferences between diurnal or nocturnal periods were found in their upstream movements. From the environmental variables considered, mean daily flow explained most of the variation in the number of cyprinids and trout, whereas moon phase and daily accumulated rainfall were more important variables for the eel movements. Although, the lift was found to be non-selective for the most abundant fish species found on the main river downstream, size-related differences were detected as the smallest size-classes were underrepresented in the lift, whereas the larger individuals were observed in greater abundance in the facility. Comparing species abundance from video recordings with periodic electrofishing samples provided a useful tool to assess efficacy of the fish lift, although biological requirements of each species should also be taken into account in the assessment. This study proved the efficacy of the fish lift for passage of all potamodromous species. For the eel however, efficacy remains inconclusive as further research is needed to quantify escapement rates and survival through hydropower turbines of descendent silver-phase stages. In view of the obtained results, several operational measures are discussed to further improve fish lift performance.

4 Introduction River fragmentation caused by instream obstacles has been cited as one of the major threats to aquatic biodiversity, including freshwater fishes (Nilsson et al. 2005). In particular, the construction of dams for hydroelectric power generation has resulted in modifications of the natural flow regime, in habitat fragmentation and ultimately in the decline or even extinction of many fish species due to the blockage of their migratory movements (Aarts et al. 2003). Consequently, fish transfer devices, commonly known as fishways, have been developed to limit the impact of dams on fish species (Clay 1995) in a tentative to partially restore longitudinal river connectivity. The hydroelectric power plants of EDP Production (EDP Group) are distributed by three large production centres in Portugal: Cávado-Lima, Douro and Tejo-Mondego. The Touvedo dam is one of the 18 power plants in the Cávado- Lima Production Centre (Fig.1). Fig.1. Map of the location: Touvedo dam The Touvedo Dam, commissioned in 1993, was provided with a fish lift, in order to maintain the upstream migration fish along with other local freshwater fish populations. Nevertheless, the fish lift performance had not been yet evaluated, namely the operation of the fish collection system. The entrance to the collection system is generally considered to be the most important part of any fishway (Clay, 1995). Although the migration of anadromous species has been studied extensively in other countries, especially salmonids (McKoewn, 1984), much less information is available on the displacements of eels and resident cyprinid fishes (Lucas et al., 2000). Their ability to use fish passes as well as their behaviour when facing an obstacle is virtually unknown. The Touvedo fish lift was initially monitored from March 1998 to February The data on fish use were analysed to provide general information on passage patterns and was integrated with other information on hydraulic parameters. The present study is part of an optimization action plan (August 2011 to February 2014) with the goal of evaluating the fish lift performance and improving the longitudinal connectivity for eels and potamodromous cyprinids. In this paper we present the results of the first stage, from September 2011 to August 2012, namely the fish lift performance before the implementation of measures. 1 Touvedo Dam and fish lift The hydroelectric powerplant of Touvedo is located on the river Lima, northwest Portugal (Fig. 2). It was commissioned on 1993 to modulate the high flows turbined at the Alto Lindoso dam (250 m 3 /s at full load) located 16 km upstream on the Portuguese-Spanish border, by storing them temporarily before returning them to the river with flows lesser than 100 m 3 /s. The dam has an installed capacity of 22 MW, and creates a reservoir with 4.5 hm 3

5 of useful capacity, covering the counties of Arcos de Valdevez and Ponte da Barca. Mean annual production if of 78 GWh. 1-Reservoir 2-Penstock 3-Powerhouse 4-Tailrace Fig.2. Touvedo dam and hydraulic scheme Touvedo dam is provided with a fish lift located in the tailrace area of the powerhouse (Fig. 3). Its main purpose is to maintain the upstream migration of anadromous fish and local potamodromous fish fauna. The lift is provided with three entrances, for which attraction is achieved by discharging a maximum flow of 4.5 m 3 /s, equally distributed among them. The stream creates a flow in the attraction circuit (channel), against which the migrating fish swim. Once in the circuit, the fish swim towards and eventually into the lift cage, which is periodically raised (in 4h intervals or whenever the powerhouse starts/stops operating) and emptied upstream of the plant into a transfer canal (upper channel) through which fish pass into the reservoir. Fig.3. Fish lift three dimensional schemes

6 2 Study A working group composed by Portuguese water forestry authorities, the national water authorities and EDP was created to define an action plan to evaluate the use and performance of the Touvedo Fish Lift and to define the necessary measures to improve and assure the operation of the infrastructure, according to EDP s environmental commitment and the Eel Management Plan (Regulation n. º (EC) 1100/2007). The proposed action plan for the optimization of Touvedo Fish Lift has three distinct stages and has been implemented by EDP Generation, Labelec and a scientific partner, the Instituto Superior de Agronomia. In this paper we describe the main results of the first stage. 2.1 Stage 1 Implementation of an annual monitoring program (August 2011 to July 2012) to assess the actual lift performance, as follows: 1 Video recording monitoring; 2 Getting monthly electrofishing fish samples downstream Touvedo dam for the quantification of the potential migrant population. The relationship between the number of individuals observed in the device and the ones captured downstream is used as a rough indicator of the efficiency of the lift for the target species selected; 3 Hydraulic characterization of the attraction channel; validation of the previously estimated values for the different operation situations using project data and the power of the attraction flow pumps. 2.2 Stage 2 Definition and implementation of measures defined using the data obtained at Stage Stage 3 Implementation of a new annual monitoring program to evaluate the success of the implemented measures. 3 Material and methods The first stage of Touvedo fish lift action plan was a diagnosis of the fish passage, namely an evaluation of the performance and structural characteristics. Video recording monitoring and fish sampling downstream. From August 2011 to July 2012, the fish lift was continuously monitored with an automatic video-recording system in combination with monthly electrofishing samplings (pulsed DC, 400 1,000 V, SAREL model WFC7-HV, Electracatch International, Wolverhampton, UK) undertaken in a 340m river segment immediately below the dam (Fig. 4). The dowstream part of the river segment (200m long x 30m wide x 3.5m deep) was sampled by boat and focused on the margins, whereas the upstream shallower part (140 m long x 25m wide x 0.5m deep) was sampled by wading with single passes according to CEN (2003) standards, to encompass multiple habitat types (riffles, pools). In order to monitor fish passage through the fish lift, a video camera (Bosch, mod. MR700) and an automatic video recorder system (Bosch, mod. LTC455) were installed in the Touvedo facilities, near the transfer canal leading to the reservoir. The camera was placed on the top of the fish lift, allowing the collection of lift cage images during the final ascension. In order to obtain clearer images for identification and estimates on fish lengths, the cage was sealed with 20 x 20 cm white quadrats. Fish identification was based on morphological trait characteristics (e.g. body shape, configuration of pectoral and caudal fins, ratio head/body size, swimming behaviour, etc.) of species predisposed to use the lift in accordance with seasonal captures downstream the dam. Video records were stored in DXA files which were subsequently analysed by the Bosch Divar Archive software player. Collected fish data

7 included the timing of each passage cycle event, the number of fish per cycle and the estimated total length of individuals. Hydraulic parameters (turbined, spillway and ecological flows) were also collected from the power plant records and throughout the monitoring process to further correlate with fish activity in the lift. Fig. 4. Location of the dowstream part of the river Lima that was sampled (Image 2012 GeoEye; 2012 Google) Hydraulic characterization of the entrance collection system was implemented through an Acoustic Dopler Velocimeter (ADV SonTeK FlowTracker) in order to assess species ability to overcome existing velocities at the entrance and in the attraction circuit. For this purpose, the ADV was installed in graduated 3m rod and for each entrance of the fish lift (Fig 5), 9 points distributed across the sectional area were selected for further measurement. The registered velocity at each of these points corresponds to the average of a sample that lasts 60 seconds. Tailrace Upper channel Fig. 5. Fish lift longitudinal scheme, showing the location of the three entrances (W1, W2 and W3) and the attraction circuit.

8 4 Results A total of 3389 individuals from 5 species were transferred by the lift. Cyprinids were the dominant group collected accounting for almost 90% of the total movements, with Northern straight-mouth nase (54.1%) being the most abundant species, followed by the European eel (35.6%). Both Iberian barbel (7.7%) and brown trout (2.5%) accounted for 10.2% of the fish movements, whereas the anadromous sea lamprey was rarely observed (Fig.6) Species Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Total % Barbel L. bocagei Nase P. duriense Trout S. trutta Eel A. anguilla Lamprey P. marinus Total Fig. 6. Number and proportion of species that successfully used the fish lift between August 2011 and July All species used the fish lift independently of time of day, as no significant preferences between diurnal and nocturnal periods were found in their upstream movements (P > 0.05; paired t-test) (Fig.7). Species Day Night t P 6 am-6 pm 6 pm-6 am Nase , ns Eel , ns Trout , ns Barbel , ns Fig.7. Results of the t-tests comparing mean number of individuals/cycle that used the fish lift during day and night. No significant relationship was found between the number of nase (r = , P> 0.05) and eel (r = ; P> 0.05) per cycle and the attraction flow that precedes the lift ascension. Contrarily, a positive association was found for barbel (r = ; P< 0.001) and marginally for the trout (r = , P< 0.10), as both species, particularly the former, seemed to display a higher use of the facility with increasing flow. The fish lift showed low species selectivity, as the most 4 abundant taxa that used the facility (nase, eel, barbel and trout) were also captured in the river segment immediately downstream (Fig. 8) With regard to the size-class selectivity, the comparison between species length distribution observed in the lift, with those of individuals caught downstream in the river, revealed significant differences for all taxa (Mann-Whitney test, P <0.05), being the smallest size-classes under-represented in the lift, whereas the larger individuals were observed in greater abundance in the facility relatively to the river segment.

9 Fig. 8. Relative abundance (%) of species size-classes that were observed on the fish lift and correspondent numbers concerning individuals captured downstream in the river. In the next graph (Fig.9) the ratio between the mean number of individuals that used the fish lift and the corresponding mean number captured in the river downstream is presented, as a rough indicator of the efficacy of the fish lift. For the barbel, and considering the periods of species increased activity on the lift (autumn 2011 and spring 2012), the maximum ratio on autumn was 0.30, i.e. for each three individuals present downstream, one successfully used the lift. In November 2011 and June 2012, it was not possible to define the corresponding ratio due to the absence of individuals captured downstream. On May 2012, the highest ratio for this species was 1.40, i.e. fishes used the facility in greater abundance, relative to the potential population size downstream. Nase ratios ranged between 0.33 and 0.70, during the period when almost all movements (c. 93%) took place, i.e. between August and October 2011 and in July Outside this period, the number of individuals which used the lift was very low, and hence the corresponding efficacy ratios. Trout used the lift regularly throughout the year at low densities and therefore showed relatively low ratios accordingly (the highest was 0.18 in November 2011). The eel, for which the period of greatest movement activity was similar to the nase (i.e. > 90% displacements occurring between August and October 2011 and in July 2012), showed low ratios, the highest ones in August 2011 (0.21) and in October 2011 (0.13), corresponding respectively to the first and second top ranked months in abundance of observed individuals.

10 Fig.9. Monthly ratios between the mean number of individuals that used the fish lift and the corresponding mean number captured in the river downstream. Mean velocities in the three entrances of the fish lift ranged between 0.28 m/s and 0.40 m/s with the powerhouse off (Fig.10). When the powerhouse operated at half-load (50 m 3 /s) a velocity increase was detected on entrances W1 (0.50 m/s) and W2 (0.58 m/s), but not on W3 (-0.06 m/s), which revealed a significant decrease with most of the measurement points (5/9) presenting negative values. In the situation of powerhouse operating at full-load (100 m3/s), only W3 is functional, while W1 and W2 remain close to increase attractiveness. In this situation mean velocity at this entrance was of 0.64 m/s. Overall, these velocities are within the range of critical swimming speeds for most of the fish species that use the fish lift. Eels have lower swimming abilities than barbel and trout, and most of the population (85%) used the facility when the powerhouse was off. Contrarily, barbel and trout are rheophilic species, for which critical swimming speeds are typically higher (0.80 m/s for the barbel; Mateus et al.2008; up to 1.20 m/s for the trout, Tudorache et al. 2008). Powerhouse condition Off (0 m 3 /s) Half-load (50 m 3 /s) Full-load (100 m 3 /s) Fish lift entrances W1 W2 W ± ± ± ± ± ±0.23 NA NA 0.64±0.15 Fig.10. Mean ( SD) velocities at the fish lift entrances according to powerhouse conditions. Next, a series of measures is presented with the aim of increasing the effectiveness of the fish lift, as well as to improve future monitoring actions and dissemination of results to the wide research and public community. These are presently being implemented and include: - reducing the spacing between the screens of the cage to avoid escapement of the smallest eels and fish size-classes;

11 - scheduling maintenance and intervention actions in the lift to the period of the lowest fish activity (November- March); - Installing a permanent barrier of approximately 100 meters in the upstream Touvedo reservoir, with sufficient fine screens for preventing clogging and debris accumulation in the exit of the fish channel; - Installing of a foam removal device (blower or water jet) to eliminate periodic foam accumulation in the lift cage; - Stabilization of the lift rises to periods of 4 hours, regardless of changes in the exploration of the powerhouse; - opening of the W3 entrance and closure of entrances W1 and W2 during operating periods of half-load (50 m 3 /s); - Increasing surveillance actions in the immediately downstream area of the lift fish entrances; - mapping and characterization of all instream obstacles (weirs, water mills, etc.) to fish migration dowstream from Touvedo reservoir; - Placement of a water temperature probe in the fish lift entrance area for continuous monitoring of this parameter to allow for further correlations with fish movements; - Promotion of awareness actions with dissemination of results, aimed at local authorities and to the wide public community. Acknowledgments The authors would like to thank João Oliveira, Rui Rivaes, Raul Arenas for help in the field work conducted during fish sampling occasions and Jose Araujo technician from edp in Touvedo Dam. References 1. Nilsson C., Reidy C.A., Dynesius M., Revenga C. (2005). Fragmentation and flow regulation of the world s large river systems. Science 308: Aarts B.G., Van Den Brink F.W., Nienhuis P.H. (2003). Habitat loss as the main cause of the slow recovery of fish faunas of regulated large rivers in Europe: the transversal floodplain gradient. Regulated Rivers 20: Clay, C.H., 1995: Design of fishways and other fish facilities, 2nd edition. Lewis Publishers, Boca Raton, Florida. 4. Lucas, M.C.; Mercer, T.; Peirson, G.; Frear, P.A., 2000: Seasonal movements of coarse fish in lowland rivers and their relevance to fisheries management. In: Management and ecology of river fisheries. Ed: I.G. Cowx, Blackwell Science, Oxford, UK. pp McKoewn, B.A., 1984: Fish Migration. Timber Press, Portland, Oregon. 224 pp. 6. CEN (Comité Européen de Normaliation) (2003) Water quality: sampling of fish with electricity. CEN, European Standard EN European Committee for Standardization, Brussels. 7. Mateus, C.S., Quintella, B.R., Almeida, P.R., The critical swimming speed of Iberian barbel Barbus bocagei in relation to size and sex. J. Fish. Biol. 73, Tudorache, C., Viaene, P., Blust, R., Vereecken, H., De Boeck, G., A comparison of swimming capacity and energy use in seven European freshwater fish species. Ecology of Freshwater Fish 17,

12 The Authors U.M. Cabral graduated in Environmental Engineer, working in the maintenance and implementation of the SIGAS in the EDP Cávado-Lima Hydro Production Center, in the Hydraulic Division since 2008, as a specialist in management and consulting, in the environment and safety issues. A.L. Marinho graduated Mechanical Engineer working in the Operation and Maintenance in the EDP Cávado-Lima Hydro Production Center since 1992, and as a sub-director in the same Center with the responsibility of the maintenance since E.M. Branco graduated in Chemical Engineer working in the Maintenance and implementation of the SIGAS in the EDP Hydraulic Division since 2006, with a long experience in management and consulting in environment and chemical issues. J.M. Santos graduated in Forestry Engineering in His PhD (2004) was focused on the effects of flow regulations on fish population and communities and the role of different types of fish passes. He is an assistant researcher at Instituto Superior de Agronomia, Technical University of Lisbon. His research interests focus primarily on ecohydraulics, fish passes and freshwater fish ecology. J. Pádua graduated in Biology from the University of Lisbon and masters in Natural Resources Management from the Technical University of Lisbon