No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Ecological impacts of small hydropower plants on headwater stream fish: From individual to community effects
Abstract
Hydroelectricity is increasingly used worldwide as a source of renewable energy, and many mountain ranges have dozens or hundreds of hydropower plants, with many more being under construction or planned. Although the ecological impacts of large dams are relatively well known, the effects of small hydropower plants and their weirs have been much less investigated. We studied the effects of water diversion of small hydropower plants on fish assemblages in the upper Ter river basin (Catalonia, NE Spain), which has headwater reaches with good water quality and no large dams but many of such plants. We studied fish populations and habitat features on control and impacted reaches for water diversion of 16 hydropower plants. In the impacted reaches, there was a significantly lower presence of refuges for fish, poorer habitat quality, more pools and less riffles and macrophytes, and shallower water levels. We also observed higher fish abundance, larger mean fish size and better fish condition in the control than in impacted reaches, although the results were species-specific. Accordingly, species composition was also affected, with lower relative abundance of brown trout (Salmo trutta) and Pyrenean minnow (Phoxinus bigerri) in the impacted reaches and higher presence of stone loach (Barbatula quignardi) and Mediterranean barbel (Barbus meridionalis). Our study highlights the effects of water diversion of small hydropower plants from the individual to the population and community levels but probably underestimates them, urging for further assessment and mitigation of these ecological impacts.
... Community size-spectra are an ataxic approach based on distributions of fish abundance among body size classes. Log-abundance generally decreases (slope) linearly with increasing log-body size through internal food web factors and abiotic ecosystem drivers (Benejam et al., 2016(Benejam et al., , 2018Broadway et al., 2015;Emmrich et al., 2011;Mehner et al., 2016;Murry & Farrell, 2014). Community size-spectra have two primary parameters, the slope and elevation of the linear model, which each have direct biological meaning (Daan et al., 2005;Sweeting et al., 2009). ...
... Nested within this framework are populations of individual species represented by all size or age classes that were susceptible to sampling (Broadway et al., 2015). Annual variation within a system and between systems in food web capacity and efficiency has been linked to internal food web composition and environmental drivers in freshwater systems (Benejam et al., 2016(Benejam et al., , 2018Broadway et al., 2015;Clement et al., 2015;Emmrich et al., 2011;Murry & Farrell, 2014). For example, ecological efficiency increased (the slope became shallower) after a regime shift from piscivore to benthic invertivore dominance within the largest size classes (Broadway et al., 2015). ...
... Tropical reservoirs have been relatively poorly studied and differ in many fundamental ways from more well-studied temperate systems. While it is well understood that warmer year-round water temperatures and bright sun promote high year-round primary production and decrease the seasonality of fish reproduction Waters & Noble, 2004), many other relationships (such as watershed and reservoir characteristics' influence on fish assemblage stability, production, and diversity) that are more thoroughly studied in temperate lakes and reservoirs (Clement et al., 2015;Emmrich et al., 2011) are relatively poorly understood for subtropical and tropical systems (but see Benejam et al., 2016Benejam et al., , 2018. The CSS approach may facilitate our study of these relationships by providing a simplifying framework for aquatic communities (Petchey & Belgrano, 2010). ...
We developed a management framework based on community size‐spectra (CSS) to establish targets to maximize desirable gamefish. We evaluated the influence of relative abundance of fish functional groups and watershed characteristics on the slope of the CSS or ecological efficiency. Both ecological efficiency and capacity were strongly influenced by relative abundance of fish functional groups and the degree of water level variation. Steeper slopes indicated overfished gamefish populations, whereas flatter slopes indicated systems dominated by undesirable invasive large‐bodied low trophic position fish. We hypothesize that a desirable fishery would have a target range of CSS slopes that provides a deterministic community‐based framework of predictable responses to environmental and food web changes that can be used to evaluate outcomes of management actions and a means to assess annual progress toward desirable conditions.
... Captările de apă pentru microhidrocentralele care fac obiectul acestui studiu sunt localizate în 14 corpuri de apă dintre care 13 sunt corpuri de apă naturale şi unul, situat pe râul Sebeşel (RORW5.2.18.1_B1a), este puternic modificat (vezi Tabelul nr. [2][3][4][5]. Cu excepţia secţiunilor plasate în aval de captările Sâmbăta (S25), Porumbacu (S35), Aușel (S47) şi Sebeşel 2 (S38) și amonte de captarea Aușel (S48) care au stare ecologică (potențial) bună, toate celelalte secţiuni monitorizate în amonte şi aval de captările MHC-urilor au prezentat pe durata monitorizării stare ecologică foarte bună. ...
... Deşi indicele multimetric al macronevertebratelor bentonice, obţinut pe baza celor două campanii de monitorizare, încadreaza secţiunile monitorizate în stare ecologică foarte bună (cu excepţia celor din aval de captările Sâmbăta, Porumbacu, Sebeşel 2, Aușel și Aușel amonte de captare, care sunt încadrate în clasa a-II-a), remarcăm faptul că indicii FAM, ISH şi EPT prezintă valori mai heterogene, care evidenţiază efectul presiunilor antropice analizate asupra secţiunilor şi sectoarelor de râu analizate (Tabelul nr. [2][3][4][5]. ...
... Starea ecologică a corpurilor de apă în perioada de monitorizare la nivelul secţiunilor reprezentativeÎn cazul secţiunilor reprezentative din sistemul naţional de monitorizare a stării corpurilor de apă, au fost analizate 19 secţiuni, amplasate în cele 14 corpuri de apă în care sunt microhidrocentrale.Indicele multimetric al nevertebratelor bentonice încadrează toate secţiunile reprezentative din sistemul naţional de monitorizare în stare foarte bună, cu excepţia secţiunilor plasate pe râurile Dejani, Cârtișoara, Porumbacu, Sebeșel care sunt încadrate în stare bună (Tabelul nr.[2][3][4][5][6]. de asemenea, faptul că valorile indicelui EPT, cu excepţia secţiunii de pe râul Porumbacu, sunt mai mici în cea de-a doua campanie faţă de prima campanie. ...
... SHPs affect a wide variety of aquatic taxa with effects ranging from the individual to the community level (Benejam et al., 2016). At the individual level, low-flow conditions significantly reduce the density and biomass of fish (Almod ovar & Nicola, 1999;Kubečka, Matěna, & Hartvich, 1997), and negative effects on the body condition of sensitive species have been observed in impacted reaches (Benejam et al., 2016;Jumani et al., 2018). ...
... SHPs affect a wide variety of aquatic taxa with effects ranging from the individual to the community level (Benejam et al., 2016). At the individual level, low-flow conditions significantly reduce the density and biomass of fish (Almod ovar & Nicola, 1999;Kubečka, Matěna, & Hartvich, 1997), and negative effects on the body condition of sensitive species have been observed in impacted reaches (Benejam et al., 2016;Jumani et al., 2018). Furthermore, the loss of longitudinal connectivity can affect the movement of migratory fish with implications for conservation and sustainability of commercial fisheries (Couto et al., 2021). ...
... Second, we expect the fish assemblage structure to respond to flow alteration, with the undammed river dominated by rheophilic species, and the dammed river characterized by increased dominance of eurytopic and generalist species (Jumani et al., 2018). Lastly, given that SHPs affect reproduction success and body size (Benejam et al., 2016;Freeman, Bowen, Bovee, & Irwin, 2011;Jumani et al., 2018), we expect differences between the dammed and undammed river in terms of the relative contribution of juvenile size class of fish species. ...
Small hydropower projects (SHPs) are promoted as low-impact alternatives for large hydropower. SHPs are generally commissioned on small- to medium-sized mountainous rivers, often in biodiverse regions, with backing in the form of subsidies, facultative policies and exemption from impact assessments as they are considered ‘green’. However, the ecological impacts of SHPs are understudied especially in highly seasonal tropical streams of Western Ghats of India, a global biodiversity hotspot and a distinct freshwater fish eco-region. We compared SHP-affected segments of a dammed and an undammed river in the Western Ghats of Karnataka, to assess how altered flow regime affects seasonal variability in habitat and water quality, and influences fish assemblage structure. We found that flow alteration by the SHP varied between different segments of the dammed river and with season. Furthermore, the nature of flow alteration influenced habitat variability, water quality and fish assemblage response in the dammed river. We observed that the dewatered segment of the dammed river experienced a lotic to lentic shift in habitat and water quality, which favoured fish species with eurytopic affinities. Fluctuating flows in the downstream segment subdued natural variability in flow regime and created novel habitats and water-quality conditions, affecting fish assemblages. The upstream segment of the dammed river retained natural variability in habitat and water quality, but did not mimic the undammed river in terms of fish composition. We also observed potential constraints on recruitment for migratory species of fish in the dammed river. Based on our results, we suggest how the placement of dewatered segment, and timing the closure of SHP operation in dry season based on ecological thresholds are potential solutions to mitigate the impacts of the SHPs. Furthermore, we recommend effective impact assessments, and adaptive management with active interventions to maintain genetic and ecological connectivity, as key to enhance the sustainability of the SHPs.
... Often, only a fraction of the original discharge remains in the residual water stretch, which then only supports a fraction of the original fish population. This has caused species shifts and population declines [65][66][67] and as a result, sometimes even rendered whole river stretches uninhabitable. Hydropeaking plants typically store larger amounts of water and release it for electricity generation in times of peak demand, mostly in the morning and evening [24,68]. ...
... But this vast majority of small HPPs produce just 13% of global hydroelectricity, while 87% is produced by just 9% of the HPPs (typically large plants) [270]. Irrespective of their size, HPPs have substantial impacts on fish [42,65,66,271], with small schemes inherently having the highest impacts relative to their capacity. Their dams fragment rivers and block up -and downstream fish migrations [29]. ...
Gegenstand dieser Dissertation ist die Entwicklung von zwei Bewertungsinstrumenten zum Abschätzen von anthropogenen Störungen auf Fische: Das erste ist eine Sensitivitätsklassifizierung, die die Resistenz und das Erholungspotenzial einer Art gegen einen Stressor widerspiegelt. Das Prinzip basiert auf der Kombination & Aggregation von Life History Traits, die für die Resilienz der Art entscheidend sind wie z. B. maximale Größe oder Reproduktionswerte, aber auch der Migrationstyp. Diese Traits wurden einzeln je nach Typ und artspezifischer Ausprägung Perzentilgruppen zugeordnet und diese dann zu einem übergeordneten Sensitivitätswert aggregiert, der für 168 Arten bestimmt werden konnte. Von Arten mit einem hohen Wert ist eine höhere Resistenz gegenüber einem Stressor zu erwarten, ein niedriger Wert hingegen deutet auf eine geringe Resistenz aber hohes Erholungspotenzial nach Aufhebung des Stressors. Der Sensitivitätswert kann für die Bewertung menschlicher Einflüsse auf einzelne Arten, aber auch Artgemeinschaften und in einer Vielzahl von Szenarien genutzt werden wie z. B. Risikobewertungen und Umweltverträglichkeitsprüfungen, aber auch in Schutz- und Revitalisierungsbemühungen Anwendung finden. Das zweite Bewertungssystem, auf der in dieser Arbeit ein starker Fokus gelegt wird, ist der Europäische Fischgefährdungsindex EFHI, ein Evaluationswerkzeug für Wasserkraftrisiken für Fische. Dieser nutzt konzeptionelle, empirische und modellierte Daten zu den individuellen Risiken einzelner Kraftwerksbausteine und verschneidet sie mit der artspezifischen Empfindlichkeit betroffener Fische. Der Sensitivitätswert ist einer der Hauptfaktoren, die diese Empfindlichkeit bestimmen und wird um weitere Informationen wie der Körperform oder Schwimmblasenanatomie ergänzt. Der EFHI bewertet kontextabhängig einen artenspezifischen Risikowert, der dann zu einem Endergebnis zwischen 0 (kein Risiko) und 1 (höchstes Risiko) zusammengefasst wird. Der EFHI ist in ganz Europa anwendbar.
... Additionally, dams obstruct the migration of fish to spawning or feeding grounds ( Figure 4) and alter and fragment habitat, thus affecting species distributions (Jager et al., 2001;Liermann et al., 2012). Moreover, even smaller barriers such as weirs, bridge foundations, gauging stations or culverts (among other obstacles) hinder or block fish movements and affect fish populations (Benejam et al., 2014;Branco et al., 2017). In addition, the blockage is not only in the upstream direction but the way of going downstream is through the top of the weir or the spillways, in which the survival depends on the height of the obstacle and the pool depth below it ; alternatively, the case of a hydropower plan, throughout the turbines, fish is not only exposed to strikes by the blades while crossing the turbines but also to a barotrauma Carlson, 2012). ...
... Consequently, the hindrance to migrate can provoke alterations in the reproductive behavior (spawning delays or spawn in non-adequate locations) (Gosset et al., 2006;Marschall et al., 2011;Van Leeuwen et al., 2016) or in their fitness (energy expenditure, injuries, low food access, etc.) (Araújo et al., 2013;Morán-López and Uceda-Tolosa, 2020). This can lead into an alteration of the community structure by means of size population reduction, isolation of populations, diversity reduction and genetic erosion (Benejam et al., 2014;Branco et al., 2017), which can reduce their resistance against diseases and invasive alien species (Marvier et al., 2004), and lead to a drastic reduction of fish populations or even disappearance Elvira, 1996). The Iberian river's hydrology is featured by seasonality and inter-annual variability, with high flows during autumn-winter; floods occur during a few months in late autumn, winter and early spring as well as strong summer droughts (Gasith and Resh, 1999). ...
Many fish species need to move between different habitats in order to complete their life cycles. As a result, migration responds to internal and external factors, with environmental variables, such as river flow and thermal regimes, acting as the main stimuli for the onset and maintenance of migratory behavior in freshwater fish. Moreover, river fragmentation and anthropogenic alterations on these variables (e.g. river regulation) may have strong impacts on fish populations, which could be aggravated by future projections of climate change and increasing water demand. Thus, to assess these impacts and define mitigation measures, it is vital to understand fish movement patterns and the environmental variables affecting them.
Native Iberian fish fauna presents the greatest European percentage of endemism, characterized by a low number of families, with most species belonging to the Cyprinidae family. The most representative species from this family are barbels and nases, for example, the Iberian barbel and the Northern straight-mouth nase. However, scarce information exists regarding the ecological requirements of these endemic species during their upstream migration. Another important family in the Iberian Peninsula, in terms of recreational fishing and ecological traits, is the Salmonidae, the brown trout being one of the most representative salmonids worldwide. Although this species has been deeply studied, most available research has been focused on anadromous populations, and studies in the south of its natural distribution are still scarce.
The present thesis aims to cover some of these research gaps regarding upstream migration patterns of Iberian barbel, Northern straight-mouth nase and brown trout (both potamodromous and anadromous ecotypes), as well as to determine the environmental conditions which trigger these movements. In addition, this information is used to evaluate the effect of human impacts and assess the effect of mitigation measures on these species.
In order to achieve this, the long-term movement data of these three species in four different locations of the Iberian Peninsula (Porma River (León), Tormes River (Salamanca), Marín River (Navarra) and Bidasoa River (Navarra)) were gathered, analyzed and discussed. In all the studied cases, data were collected in fishways, since they are mandatory points of passage during upstream migration. Survival analysis techniques were used to study median migration dates and patterns. Subsequently, random forest regression was used to evaluate the influence of environmental variables on the number of captures, develop models that can predict when upstream movements were more likely to occur, evaluate different scenarios of river discharge and water temperature and assess the possible effects of management and restoration actions.
The long-term monitoring is an essential tool, not only for identify population changes, migration patterns and cues, but also for the evaluation of the overall effect of changes in the parameters involved in the migration and assessing the effects of mitigation measures. Therefore, continuous monitoring studies are necessary to define adaptive strategies and reliable management plans to ensure the conservation of Iberian freshwater fish.
... About half of the HPPs studied were small hydropower plants (with diversions), with an installed power capacity of <10 MW. This is remarkable, as internationally, relatively little attention has been paid to the effects of small hydropower plants, especially from headwater streams, as already stated by multiple authors [91,[103][104][105]. ...
... We demonstrate that populations of trout (Salmo trutta fario) and bullhead (Cottus gobio) have decreased or disappeared from many Carpathian headwater streams within the last 40 years, following HPP construction there. A similar pattern between impounded and unimpounded streams from headwaters was reported by Benejam et al. [105], who linked this to the ecological impacts of small HPPs on trout; these impacts affected individuals, up to population and community levels. Another study [115] found impacts on fish assemblage composition. ...
Hydropower is currently experiencing a boom in southeast Europe. For Romania, the number of hydropower plants is estimated to be between 545 and 674, but little has been published about their environmental impact. We provide the first overview of the geographical distribution of hydropower plants in Romania, supplemented by a review of current knowledge about their environmental impact, and present case study evidence on the effects of small hydropower plants on fish in headwater streams of the Carpathian Mountains.
We show that 49% of the documented 545 hydropower plants in Romania are located in Natura 2000 or other protected areas, 5% are located in water bodies with ‘very good’ ecological status, and another 12% in water bodies with ‘good’ ecological status and ‘very good’ hydromorphological status according to the EU Water Framework Directive. Second, we demonstrate that hydropower plants significantly impact fish populations in several ways, both in upstream and downstream reaches, e.g. by water abstraction, dam construction and other hydromorphological alterations. Following the construction of hydropower plants in headwater streams, trout (Salmo trutta fario) and bullhead (Cottus gobio) populations often disappeared completely, and only remained in 38% of the stream reaches either upstream or downstream of the respective hydropower plants.
In conclusion, the significant environmental impacts of each individual hydropower plant combined with the large number of them as well as the relative lack of effort to mitigate environmental impacts together represent a significant threat to aquatic biodiversity in Romania. The impacts exerted by hydropower plants are often unjustifiable by public interest according to EU directives, as small hydropower plants account for only around 3% of Romania's total electricity production. Better availability and access to environmental monitoring data are needed, as this would greatly support the development of more integrative management approaches to Romanian rivers.
... Although SHPPs are significant contributors to renewable energy, they are also associated with well-documented ecological impacts on surface water ecosystems like habitat fragmentation and biodiversity loss (Benejam et al. 2016;Lange et al. 2018;Kuriqi et al. 2021;Šarauskienė et al. 2021). In contrast, research on the impacts of SHPPs on the hyporheic zone remains scant. ...
This study investigates the ecological impact of a small hydroelectric power plant (SHPP) on the hyporheic zone of the venacquaro stream (VEN), a low‐order groundwater‐fed stream in Central Italy. The hyporheic zone, a critical ecological interface where groundwater and surface water interact, plays a pivotal role in nutrient cycling, pollutant retention, and supporting aquatic biodiversity. However, hydrological alterations from activities such as damming pose significant threats to this zone. The research employs a three‐pronged approach to assess the effect of a SHPP on hyporheic copepod communities. Copepods were selected as the focal group due to their dominance in this habitat. Initially, a generalized estimating equation (GEE) model was used to evaluate changes in copepod diversity, specifically alpha and beta diversity. The study then examines environmental shifts caused by the SHPP using permutational analysis of variance (PERMANOVA) and principal component analysis (PCA). Lastly, a multivariate species distribution model (mSDM) explores correlations between environmental variables and copepod abundances. Results reveal significant alterations in copepod assemblage structure and environmental variables downstream of the SHPP. The GEE model indicates a notable shift in beta diversity, primarily driven by disruptions in hyporheic connectivity rather than environmental changes alone. This disruption favours stygobitic species downstream, suggesting the influence of groundwater upwelling. Environmental analysis shows several differences between upstream and downstream sites, with changes in parameters such as pH, temperature, and dissolved organic carbon. The study highlights the need for effective management strategies to mitigate sediment accumulation and maintain habitat quality in SHPP‐affected streams. Techniques like sediment bypass tunnels (SBTs) are recommended to preserve both economic and ecological values. This research contributes to the still limited understanding of SHPP impacts on hyporheic ecosystems, emphasizing the importance of considering these effects in hydropower development and riverine ecosystem conservation.
... Fish species composition differs between the nature-like bypasses and modified main channels of the regulated rivers, which can be attributed to strong habitat alteration and the loss of swiftly flowing riffle sections in most regulated hydropower rivers (Gracey and Verones 2016;Zarfl et al. 2019). Pool sections are usually more abundant, and riffle sections are less abundant in dammed hydropower rivers than in free-flowing rivers (Benejam et al. 2016). At our study sites, the habitat characteristics of fastflowing bypasses resembling natural streams differed clearly from the slow-flowing main river channels upstream of the dams. ...
Nature‐like bypasses refer to fishways that simulate natural streams. Apart from facilitating fish migrations, bypasses possess the capacity to enhance biodiversity in dammed rivers. Feasibility of environmental DNA (eDNA) as a tool for bypass assessments is unknown. This study investigated fish eDNA in 10 bypasses and their main channels. Initially, the relative DNA flow‐through was estimated in bypasses. Subsequently, the impact of environmental factors and bypasses on fish assemblages was evaluated, and the robustness of the eDNA and electrofishing methods was assessed pertaining to bypass monitoring. The eDNA flow‐through was computed using an equation to estimate the residual DNA at specified distances downstream of the source site. The relative DNA flow‐through was lowest in the longest bypass with low flow rate and highest in the shortest bypass with higher flow rate and was dependent on the DNA decay rate coefficient used. The redundancy analysis revealed significant effects of spatial location, agriculture, catchment area, and bypass length on the species composition. The within‐river analyses indicated significant and nonsignificant bypass effects on species composition and total species richness, respectively. Higher richness and DNA abundance of migratory and threatened species were observed in the bypasses than in the main channels. The eDNA samples displayed higher species richness compared to electrofishing. The species composition of the bypass eDNA samples was intermediate between that of the main channel eDNA and bypass electrofishing samples, which further corroborated performance of eDNA flow‐through in bypasses. Therefore, bypass eDNA samples represented variable mixtures of local and main channel assemblages, indicating relatively low robustness of eDNA for quantitative and spatially accurate bypass assessments. Nevertheless, these results demonstrate practical applicability of eDNA in surveying the presence of desired species and evidence of the benefits of bypasses in supporting biodiversity and species threatened by damming.
... In addition, the water temperature may increase in by-passed reaches during summer due to reduced discharge. The effects of the changes in water flow and water temperature on aquatic biota may be severe (e.g., Bejarano et al., 2017;Benejam et al., 2016;Jackson et al., 2007;Pracheil et al., 2016). ...
Hydropower (HP) has become the most important renewable energy source worldwide during the last century. However, the impacts on aquatic ecosystems may be considerable. In the Northern Hemisphere, salmonid fishes are often affected by hydropower‐related temperature alterations. As their metabolic processes are entirely dependent on water temperature, they are strongly affected when the HP development reduces the water temperature during summer by extracting water from below the thermocline of upstream reservoirs. We investigated juvenile growth of Atlantic salmon Salmo salar and brown trout S. trutta in six Norwegian rivers where hydropower has considerably reduced the water temperature during summer. We used observed mass of 1+ juveniles sampled upstream and downstream the tailrace of the hydropower plant and compared these with simulated mass of 1+ juveniles based on daily recorded water temperatures and a bioenergetics model. Establishment of reservoirs have led to reduced growth of juveniles of both species on river reaches downstream HP tailraces. The hydropower development significantly altered the temperature regimes with the downstream reaches having lower temperatures than upstream reaches. Both observed and predicted masses of 1+ juveniles of both species were also lower downstream than upstream. Predicted mass were more similar to the observed mass for Atlantic salmon than for brown trout, indicating that the bioenergetics model for brown trout is not optimal.
... Accordingly, under the confluence of blockage and water reduction, the fish abundance, average size and weight have considerably decreased in rivers with small hydropower development. The existence of dams has seriously impeded the normal movement of fish, especially resulting in the decline of migratory fish population (Bakken et al. 2012;Benejam et al. 2016;Kucukali 2014;Wang et al. 2013). ...
Achieving a harmonious alignment between the biological characteristics of fish and hydrodynamics patterns is crucial for ensuring the efficacy of fish passage facilities. In this study, based on the hydrodynamic characteristics of the river and the biological characteristics of fish, we evaluated the internal flow field in the nature-like fishway of Congen II hydropower station located along the Chabao river and explored methods to improve the operation efficiency. Based on comprehensive considerations of the flow field, turbulent kinetic energy, and the migration pathways of fish, it is found that the implementation of a continuous oblique bottom slope represents a more cost-effective and operationally convenient solution. The influence of different permutation of bulkheads in the nature-like fishway on operational efficiency was further examined. Our investigation revealed that the nature-like fishway with the continuous slope of 2% and the arrangement of three bulkheads in each row (model 3) exhibited a relatively simple velocity distribution and linear flow line, which poses challenges for fish in locating resting areas. In addition, the distribution of low turbulence kinetic energy area in the mainstream made it less favorable for fish to transition from the mainstream to the rest area within the fishway. The nature-like fishway with the continuous slope of 2% and the arrangement of two or three bulkheads in staggered rows (model 4) demonstrated better performance. Several potential fish migration routes for both model 3 and model 4 were proposed based on the numerical simulation results. In model 3, fish exhibited a continuous sprint through the concentrated high-speed area, which was less favorable for fish to rest and forage. In contrast, model 4 exhibited a diversified flow velocity distribution, enabling fish to make timely changes in their direction during migration. This feather proved to be advantageous in enhancing fish migration within the passage. The design of nature-like fishway in this study provides an important reference and technical support for the construction and optimization of the nature-like fishway for low dams, and is of great significance for restoring river connectivity destroyed by small hydropower construction and improving fish migration.
... Notably, the number of hydropower projects increased from 59 to 89 between 2015 and 2019, with corresponding total installed capacities of 10,017 MW and 12,285 MW, respectively (Mekong River Commission, 2018a, n.d.). Previous studies consistently underscore the strong negative impact of hydropower dams on fish biodiversity, communities, and distribution, especially for migratory species (Benejam et al., 2016;Jellyman and Harding, 2012;Ngor et al., 2018a;Nuon et al., 2020;Sor et al., 2023). In contrast, climate change emerged as the primary driver of changes in fish suitable habitats in the Mekong Basin, leading to both habitat contraction and expansion. ...
Global changes are causing significant alterations to terrestrial, marine, and freshwater ecosystems worldwide, with substantial implications for plant and animal populations, potentially leading to species extinctions. While freshwater ecosystems are recognized as particularly vulnerable to these impacts, there has been limited research conducted in tropical regions on how these changes will affect them. Here, we assessed the relative impacts of change in climate and human population density on fish species distribution between current (1970-2000) and future (2050s) time periods in the Mekong River. We analyzed occurrence data for 195 fish species from 10 functional guilds and employed species distribution models (SDMs) to evaluate potential changes in fish species distribution under the independent and combined impacts of changes in climate and population density. Our results show that climate change, with significant change in temperature and precipitation rather than minor population shifts, will be the primary driver of future change in fish species distribution in the Mekong River with all fish guilds likely to expand their suitable habitats. However, contrasted distributional changes were observed among fish species, with certain guilds projected to gain more suitable habitat than others. Out of the 195 species examined, the majority of fish species studied (i.e., 84 %) are expected to undergo a northward distributional shift, while 49 species may experience a reduction in their suitable habitats. Additionally, significant declines in species richness are projected to occur in currently diverse areas (i.e., Tonle Sap Lake and River), while the highest increases in fish species richness are projected to occur in the 3S (Sesan, Sekong, and Srepok) River Basins. These findings highlight potential hotspots for mitigating the impacts of environmental changes, providing an opportunity for conservation practitioners and planners at the national and regional levels to develop and implement adaptation and mitigation measures.
... Reasonable and effective river development projects can bring energy benefits and optimize water resource allocation (Tan et al., 2019). However, the river ecosystem will be greatly impaired due to the construction and operation of these large-scale river development projects (Benejam et al., 2016;Yuan et al., 2021;Zhang et al., 2022), thereby perhaps affecting fish survival and behaviors in corresponding basins. Although little research has been carried out to investigate the effects of river development projects on fish behaviors, it is necessary to further analyse the inevitable impact of environmental degradation caused by river development projects on fish behaviors. ...
Dam construction alters the hydrodynamic conditions, consequently impacting the swimming behavior of fish. To explore the effect of flow hydrodynamics on fish swimming behavior, five endemic fish species in the upper Yangtze River basin were selected. Through high‐speed video visualization and computer analysis, these species' swimming patterns under different flow velocities (0.1–1.2 m/s) were investigated. The kinematic and morphological characteristics of the fish were presented. The principal component analysis was used to analyse the main factors influencing the swimming ability of fish and to determine the correlation coefficients among fish behavior indicators. Fish exhibited three different swimming patterns under different flow velocities. Low velocity (0.1–0.3 m/s) corresponds to free motion, middle velocity (0.4–0.7 m/s) corresponds to cruising motion, and high velocity corresponds to stress motion (0.8–1.2 m/s). The fish kinematic index curves were obtained, and four of five fish species showed two extreme points, which means the optimal and adverse swimming strategies can be determined. With the increase in flow velocity, the tail‐beat frequency showed an increasing trend, whereas the tail‐beat angle and amplitude showed a decreasing trend. Morphological and kinematic parameters were the two main indexes that affect the swimming ability of fish, which accounts for 41.9% and 26.9%, respectively.
... In the Brazilian Pampa, more than 50% of the small to medium watersheds (Strahler order 2 to 3) are under intermediary to high environmental pressure (Meneses 2016), mainly due to natural vegetation being converted to agriculture and forestry, and also due to livestock use. Loss of watershed and riparian integrity in pampean streams affects size structure of fish communities (Benejam et al. 2016;Pott et al. 2021), and fish functional and taxonomic diversity (Chalar et al. 2013;Dala-Corte et al. 2016Mello 2017;Moi and Teixeira-de-Melo 2022), resulting in local extinctions (Zarucki et al. 2011;Camana et al. 2020). ...
In this chapter, we compile information on the freshwater fish species found in the Pampa region north of the La Plata river in Brazil and Uruguay, as well as the highland grassland enclaves in the southern part of the Atlantic Forest. This geographical area encompasses seven distinct freshwater ecoregions, which exhibit a relatively low proportion of shared species. This leads to a high level of regional species diversity, comparable to other ecoregional groups of tropical South America. The grassland ecosystems of the Pampa and highland grasslands collectively host 570 freshwater fish species. Among these, 334 species are known to occur in the Pampa to which 102 (30.5% of the total) are endemic. Annual fishes (Rivulidae) are an important component of the pampean fish fauna, both because of their high species richness, estimated at around 40, and their significant contribution to the endemic fish species in the Pampa, accounting for approximately 44.1% of all endemic fish species in the region. In addition, a significant proportion of the species (27) are currently categorized as highly endangered. Environmental pressures derive mainly from land use changes, but also include drainage modifications, wetland loss, mining, species invasions and pollution. Conservation efforts aimed at protecting the fish species of the Pampa have been insufficient, albeit important initiatives such as the development of regional and national red lists of threatened species have been implemented. Existing protected areas are limited in number and cover a relatively small portion of the region. Furthermore, they do not adequately represent the diverse ecoregions and aquatic habitats found in the Pampa.
... In similar research investigating the effects of the Çambaşı RoR-HEPP on the physicochemical water quality, it was reported that the power plant changed most of the water quality parameters negatively and significantly between the pre-regulator (before) and the tailwater outlet (after) including TSS, EC and TDS for 107%, 102% and 39%, respectively (Verep and Çalış, 2021). Changes in sediment quantity and/or distribution can negatively impact the habitat composition and morphology of stream systems because sediments -whether transported or deposited-play a significant role in the number and health of ecosystems as well as the biodiversity in and around the stream bed (Benejam et al., 2016;Hauer et al., 2018). When all types of HEPPs are constructed, the natural dynamic equilibrium, which is characterized by a continuous interplay between erosion, deposition, and remobilization of material, is disturbed (Hayes et al., 2018;Agrawal et al., 2011). ...
... The development of irrigation systems has a direct impact on local aquatic resources [77], adversely affecting aquatic fauna, especially fish [78][79][80][81]. The shrinkage of the Tonle Sap Lake has been attributed to climate change [82][83][84][85][86]. ...
Irrigated agriculture is indispensable to the Lower Mekong River Basin (LMB), which ensures food security and provides livelihoods for tens of millions of people. Irrigation, agricultural production, hydropower and aquatic ecosystem health are intertwined in LMB, so it is necessary to adopt a holistic approach to analyze irrigation problems. Here, we discuss the challenges and opportunities of LMB irrigation. Bibliometric analysis is carried out to determine the characteristics and patterns of watershed irrigation literature, such as the importance of authors, affiliated institutions, and their distribution in China. Based on bibliometric analysis, research topics are determined for thematic review. Firstly, we investigated the factors that directly affect the demand and supply of irrigation water and associated crop yield impacts. Secondly, we analyzed the influence of water availability, land use and climate change on agricultural irrigation. Thirdly, we analyzed the adverse effects of improper irrigation management on the environment, such as flow pattern change, ecosystem deterioration and land subsidence caused by groundwater overexploitation. Fourthly, the time–space mismatch between water supply and demand has brought serious challenges to the comprehensive water resources management in cross-border river basins. In each specific application area, we sorted out the technologies in which remote sensing technology is used. We hope that this review will contribute to in-depth research and decision analysis of remote sensing technology in agricultural irrigation.
... The construction of dams and other barrage hydraulic structures has caused a certain degree of damage to river ecology while meeting the needs of social development [1][2][3][4][5]. The original continuity of the river is blocked by hydraulic engineering, which seriously threatens the reproduction of migratory fish [6]. ...
To imitate the constraints of topographic conditions, turning pools with different angles, such as 90° and 180°, are set in fish passage arrangements. If the mainstream in the turning pool is close to the wall and the recirculation zone is too large, it will have an adverse effect on fish migration. Taking the 180° turning pool as an example, five types of arrangements without and with additional rectifier baffles are proposed to optimize the body shape of the turning pool. A three-dimensional numerical simulation method is used to compare and analyze the different arrangement schemes. The results show that adding rectifier baffles can adjust the flow structure in the 180° turning pool. The arrangement adding rectifier baffles at the two three-equidistant points of the 180° turning pool and tilting 15° inward outperforms others in this study. This arrangement can center the mainstream, reduce turbulent kinetic energy, significantly decrease the flow velocity along the course, downscale the recirculation zone, and decrease the overall flow velocity.
... Moreover, the tributary from the fragmented zone, i.e., Basochhu is an impacted area having existed as dewatered reach for more than two decades. Such modification of rivers alters flow regime, and habitat conditions and restricts migration of fish to life-stage specific habitats (Bunn and Arthington 2002;Benejam et al. 2016;Zhang et al. 2018;Moreno-Arias et al. 2021) resulting in the decrease of Kn over the years in hydropower impacted areas (Steffensen and Mestl 2016;Nyanti et al. 2021) due to the reduced food availability, increased temperature and increased energy demands of fish under reduced flow condition in dewatered reach (Steffensen and Mestl 2016;Poletto et al. 2018;Nyanti et al. 2021). ...
This study aimed to determine the length-weight relationship (LWR) and access the relative condition factor (Kn) of migratory fish, Schizothorax richardsonii and resident fish, Garra gotyla from the tributaries of Punatsangchhu River within the vicinity of the hydropower development area. The sampled tributaries were categorized into three zones: upstream, fragmented or impacted zone and downstream zone. Both species indicated significant negative allometric growth. The allometric form of LWR for S. richardsonii and G. gotyla is established as W = 0.0155L 2.6806 and W = 0.0161L 2.7506 , respectively. The K n of both species were > 1 at the downstream zone only. One-way ANOVA and Tukey HSD test indicated significantly lower Kn in the fragmented zone and upstream zone as compared to the downstream zone for S. richardsonii. An unpaired two-sample t-test indicated insignificant differences in Kn of G. gotyla between the downstream and fragmented zone. This study reflects the greater impacts of hydropower development on fragmented zone and migratory fish as compared to resident fish. The present study will help in the improvement of long-term monitoring of the impacts of hydropower development on fisheries and standardization of fisheries monitoring programs in Bhutan.
... Indeed, barriers interrupt fish dispersion routes and modify natural environmental conditions of fish habitats, impeding completion of their life cycles [2,14]. Therefore, when longitudinal connectivity decreases in a river network, often, the abundance of fish species decreases and local extinctions may occur (i.e., [15][16][17]). These effects in local fish assemblages may be driven directly by fragmentation, but also by changes in environmental conditions (e.g., water quality) and flow regime [18,19]. ...
Longitudinal connectivity is the main attribute of river ecosystems and is essential for the maintenance of aquatic biota. When longitudinal connectivity decreases in a river network, abundance of some fish species decreases, and local extinctions may occur. Such abundance decreases and extinctions affect local assemblage structure (alpha diversity) and result in a high degree of dissimilarity among local assemblages (higher beta diversity). Specific ecological mechanisms that are behind these biodiversity changes induced by connectivity loss remain poorly understood. Here, we assessed the effects of fragmentation at the local and basin level, as well as local environmental variables on local fish diversity patterns in eight Andean river basins in central Chile (32-39 • S). The results indicated that fish assemblages inhabiting pool habitats in highly fragmented basins were characterized by significantly lower species richness and alpha diversity mainly driven by absence of fish species with high dispersion capacities. Our results highlight the importance of the effects of barrier cascades upstream as drivers of local native fish diversity. Sustainable hydropower development necessitates system scale planning of the placement of future barriers and should consider both local and basin scale biodiversity indicators.
... Flow modification may mean daily rapid changes in flow (e.g., hydropeaking) or damping flood peaks (e.g., dams for flood control) (Almodóvar & Nicola 1999). These non-natural flow variations might affect the density, growth, biomass and species composition (Almodóvar & Nicola 1999, Benejam et al. 2014, Puffer et al. 2015, as well as affect the daily fish behaviour and the time of spawning and migration periods (Karppinen et al. 2002). ...
A literature review of climate change on salmonid fish species was made with a special interest on regulated rivers. As a case study, the effect of expected climate change on fish in the River Vuoksi was assessed. The overall impact of climate change on salmonids in the River Vuoksi was considered negative. Being a lowland river, maximum water temperatures in summer may already exceed critical limits for brown trout and landlocked salmon parr, and grayling at all life-stages. Expected increase in winter and early spring discharge of the River Vuoksi in the following decades was considered harmful especially for brown trout and landlocked salmon juveniles. Expected decrease in summertime discharge accompanied with low water velocities will aggravate the loss of riffle habitat preferred by Salmo spp. young especially in these restored riffle areas. In contrast to salmonids, several warm-water species (e.g., pikeperch and many cyprinids) dwelling mostly outside the few remaining rapids and riffles in the River Vuoksi are anticipated to benefit from the climate change. The River Vuoksi was considered to carry a special risk of a self-sustaining rainbow trout establishment in warming climate because of its southern location, expected changes in yearly discharge, relatively high and stable pH and large size of the river. Even without establishing a self-sustaining population, the widely detected spawning behavior of introduced rainbow trout with redd construction may be harmful to the reproduction of brown trout and landlocked salmon. Hence, stocking of put-and-take rainbow trout to the River Vuoksi was considered as a risk. As mitigation measures for the adverse effect of climate chance on the salmonid species can be suggested restoration of the existing riffles, increased connectivity and new reproduction areas by construction of bypass channels for the fish to pass dams, shadowing tree canopy to possible bypass channels, dampening of hydropeaking, and more effective control of the fishermen in obeying the fishing restrictions especially in the lower reaches of the River Vuoksi.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
This open access book presents (selected) new and innovative developments for sustainable and fish-friendly hydropower. It offers unique insights into the challenges, practices and policies of hydropower developments across 8 European countries, providing examples from on-site studies and European-wide analyses. The case studies throughout the book are practical “real-world” examples, which are intended to serve as inspiration for anyone who would like to know more about how solutions for more sustainable hydropower production can be designed and implemented.
Hydropower is an important renewable energy source, which, however, can also impact aquatic ecosystems, fish populations and hydro-morphology. EU and national water, environmental and energy legislation strive for sustainable energy and water resource management as well as the protection of important habitats and species. These have an effect on the requirements and decision making processes for hydropower planning, commissioning and operation. With a high variety of measures existing and site-specific conditions as well as national and EU level legal requirements to consider, it can be difficult to determine, what issues to address and which measures to implement.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
The proliferation of hydropower development to meet obligations under the Renewable Energy Directive has also seen the emergence of conflict between the hydropower developers and the fisheries and conservation sectors. To address this trade-off between hydroelectricity supply and its environmental costs, this chapter introduces a series of tools and guidance to assess environmental hazards of hydropower in particular on fishes, to enhance assessing cumulative effects from several hydropower schemes and to enable informed decisions on planning, development and mitigation of new and refurbished hydropower schemes. The newly developed European Fish Hazard Index is introduced as objective, comparable, and standardized screening tool for assessing the impacts on fishes at existing and planned hydropower schemes, while explicitly considering the ecological status and consecration value of the ambient fish assemblage. In addition, guidance is provided on assessing the environmental impacts of consecutive hydropower schemes in a river system. This guidance separates between cumulative impacts on habitats and species and thus, considers cumulative length of all impoundments in a river system, total fragmentation by barriers (barrier density), but also different migratory life history traits of species and their encounter probability with hydropower schemes and sensitivity to mortality. Finally, a decision support scheme is provided to balance the environmental risk with appropriate, site-specific mitigation planning and implementation at new and existing hydropower schemes.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
The findability of fishpasses is one of the keys in the design of functional migration facilities. In the pre-alpine test case HPP Altusried, an agent-based model (ABM) has been used to identify preferred migration corridors of fish approaching the downstream entrance of the installed fishway. Detections of tagged barbel and grayling derived with an acoustic telemetry system, a 2D-hydrodynamic model as well as results from fuzzy rule – based habitat suitability modeling served as basis for the development of the ABM. Predicted swimming paths show high similarities with observed tracks of single individual fish and indicate that the probability to find the fishway in a short time depends on the lateral position of fish in the river section downstream of the entrance area.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
This chapter very briefly outlines site and constellation specific direct and indirect impacts of a hydropower scheme primarily on fishes. It describes potential effects of single elements of a hydropower scheme, such as available migration routes up- and downstream, impoundment, hydraulic head, turbine type and mode of operation. It summarises the state of knowledge, points out knowledge gaps and indicates potential mitigation options.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
The Upper Inn River is affected by hydropeaking. To mitigate hydropeaking impacts between the villages Ovella and Prutz the diversion hydropower plant GKI has been designed to buffer fast flow changes and divert water into a bypass tunnel. This Testcase enabled the comparison between the impacted and mitigated situation. We exemplify the application of the CASiMiR hydropeaking assessment module and quantify significant improvements of the fish-ecological situation.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
This chapter focuses on the topic of turbine passage as one aspect for downstream migration of fish at hydropower plants (HPP). To evaluate the impact of HPPs on downstream fish passage, it is important to quantify the mortality rate during turbine passage accurately. This chapter presents guidelines and recommendations using basic and more detailed methods. Furthermore, the results of their application while the FIThydro project at the Testcases of Guma, Bannwil, and Obernach, which are equipped with bulb turbines, are presented. Different methods to evaluate fish passage through turbines are discussed. These are modelling methods to assess the survival rate, sensor fish test at the Testcases to record physical data, as well as field tests at the laboratory Testcase in Obernach gaining a better understanding of the impact of fish behaviour on fish passage. The modelling methods reach from simple physical and empirical methods to determine the strike probability to enhanced methods including the physical reaction of the fish up to numerical simulations modelling the fish path and including behavioural aspects of the fish. The results of field tests at the Testcase sites help to improve and validate the methodologies and to develop guidelines for the application.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
Public acceptance can play an important role in determining the trajectory of hydropower development and modernization as well as the adoption of mitigation measures. Particularly in the planning stages of hydropower projects and modernization, local public resistance may delay progress and completion. For this reason, it is important to understand how to study local public perceptions of hydropower to improve project implementation and reduce public resistance. This chapter provides an overview of public perception of hydropower projects, describes methods for studying public acceptance and presents an application of the Q-methodology in four Europe case studies from hydropower-intensive regions.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
Hydropeaking negatively affects fish assemblages, but knowledge gaps still constrain our ability to rank and mitigate the impacts of different hydropower operation regimes at particular power plants. This is especially relevant for species and rivers for which the effects of hydropeaking are less investigated, such as the Iberian cyprinids and Mediterranean rivers. Therefore, a recently developed hydropeaking tool to systematically assess hydropeaking impacts on salmonids has been adapted for Iberian cyprinids within the research project FIThydro. The general tool framework developed for the salmonids was kept for the cyprinids, with the combined use of factors describing the physical effects and indicators of fish vulnerability to assess hydropeaking impact. An initial set of effect and vulnerability factors was developed for Iberian cyprinids. In addition, preliminary thresholds were established for each indicator to account for different levels of impact of hydropeaking on the focus taxa. The proposed factors/indicators and thresholds were critically reviewed by experts on Iberian cyprinids ecology and Mediterranean rivers functioning, and a final set of effect and vulnerability factors was established. The final factors retained most of the ones proposed for salmon, but included new ones, particularly for vulnerability.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
Fish passing downstream through hydraulic structures and turbines may risk dying or getting injured. Archimedes screw turbines are frequently considered more “fishfriendly” than conventional turbines. However, to date only a handful of studies assess the impact of Archimedes screws. Within the FIThydro project, we investigated injury and mortality on 2700 bream, roach and eel, including passive barotrauma sensors passing a large Archimedes hydrodynamic screw (10 m head, 22 m length) on three rotational speeds of 30, 40 and 48 Hz. The sensors measured total water pressure, linear acceleration, rotation rate, magnetic field intensity and absolute orientation. They indicated that passage is a chaotic event, and that barotrauma-related injury and mortality are indeed unlikely. Nonetheless, substantial mortality of fish was observed, specifically for bream (42%) and roach (18%) but not for eel (1%). No straightforward relation was found between rotational speeds and fish injury and mortality. The study indicates generally lower mortality and injury rates compared to conventional turbine types. However, fish can still get heavily injured or die, depending on the fish species. Therefore, we stress the need for further studies on Archimedes screws to identify the causes of the observed species-specific injury and mortality rates.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
Although the costs of fish-related mitigation measures can play an important role in the adoption of mitigation measures, there is relatively little information about this aspect. This chapter presents an overview of the range of costs for different mitigation measures and compares their magnitudes. As many mitigation measures are adopted in combination, one of the challenges related to cost analysis is the lack of disaggregated cost data. Thus, this chapter also reviews costs of adopting combined mitigation measures such as morphological changes and environmental flow. In turn, case studies demonstrate how to compare costs if multiple types of mitigation measures are adopted.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
Hydropower is at the cross-road of different policies on renewable energy, climate change, water and nature. Knowledge of current policies and regulations at different levels is crucial for understanding the framework conditions for more sustainable hydropower. This chapter examines the role of policy in planning and implementing mitigation actions for European hydropower. The overarching framework is set by European Union legislation in particular the Water Framework Directive, EU policies on nature/biodiversity and the EU agenda for energy and climate. All these different policies should be taken into account in a balanced way considering synergies and trade-offs. EU policies are complemented by national legislation that sets the regulatory framework for hydropower mitigation measures in each country. The impacts of hydropower for which mitigation is most commonly required by legislation are the disruption of upstream fish migration and the modification of flow conditions. Supported by a policy analysis of eight European countries, this chapter shows that recent changes in environmental legislation and societal pressure have reduced permit duration for hydropower plants. Further, the Water Framework Directive and national policy revisions have triggered modifications in authorisation procedures for hydropower at the benefit of implementing mitigation measures.
... At HPPs in which only a fraction of the original discharge remains in the residual river stretch severe consequences regarding water depths, flow velocities, and temperature extremes were observed. These do not support some fish populations anymore, cause species shifts and population declines Benejam et al. 2016;Habit et al. 2007) and sometimes even render whole river stretches uninhabitable. At some HPPs with state-of-the-art environmental flows of at least 10% mean annual stream flow (Huckstorf et al. 2008) these impacts are less pronounced. ...
This chapter focuses on the topic of measures to improve the fish passage through a turbine. Based on applications at the bulb units of the FIThydro Testcases of Guma, Bannwil and Obernach cost efficient and simple to apply measures are analysed. In the following two methods are presented. Applying a numerical analysis of the downstream fish passage typical physical stressor variables as strike, shear and barotrauma can be identified and correlated to the biological impact on the fish. In the FIThydro project, Voith applied the method to a wide range of operating conditions to derive fish-passage hill-charts. These allow a judgment of the physical impact on fish, dependent on the operating condition of the turbine. The studies at the Obernach lab performed by the team of the Technical University of Munich, show another method to improve fish survival rates by influencing fish pathways through the turbine. These promising results can be used for the Induced Drift Application (IDA), which are described in detail.
... The results of the fish survey are detailed in A total of 6 species of fish are collected on site, among which Misgurnus anguillicaudatus, Cyprinus carpio and Carassius auratus are highly resistant to pollution and are medium pollution zone indicator fish, indicating that there may be a certain degree of pollution in the watershed. Zhu et al. (2021) collected 71 species of fish in the nearshore Jingjiang section of the Yangtze River near the mouth; Wang et al. (2020) collected 64 species of fish in the Xinzhou waters of Anqing of the Yangtze River; Zheng et al. (2019) collected 56 species of fish in the Wuhan section of the Yangtze River, the fish resources in the survey basin are relatively small compared to the aquatic resources in the upper reaches of the Yangtze River, it is possible that the construction of small hydropower stations has led to changes in river volume and flow rate, which has affected the survival and reproduction of fish (Sun and Liu, 2020), reducing the space in the water column and affecting the species composition of fish (Benejam et al., 2016). The construction of small hydropower stations has a greater impact on fish diversity than other aquatic organisms. ...
At present, there is little research on the impact of small hydropower stations on aquatic biodiversity. In order to investigate whether the existence of small hydropower stations has a significant impact on the aquatic biodiversity of their watersheds, we conducted a systematic study on the abundance of plankton, benthic animal, fish and microorganism in the watersheds of 15 small hydropower stations in Qionglai City. The results showed that 59 species of phytoplankton from 3 divisions, 16 species of zooplankton from 4 categories, 25 species of benthic animal from 3 phyla and 30 species of fish were found in the study basin. The analysis of the physical and chemical indicators of water bodies and the distribution characteristics of aquatic organisms found that the operation of small diversion-type power stations in Qionglai City changed part of the aquatic habitat in the basin, with a greater impact on the activities of large aquatic animals (fish) and a smaller impact on plankton and microorganism, and the intensity of the impact was shown as fish > benthic animal > plankton > microorganism. The small hydropower stations in this study have an impact but not significant on the aquatic biodiversity in the Baimo and Wenjing River in the Qionglai City, and this study provides a data reference for the comprehensive assessment of the environmental impact of small hydropower stations.
... Dams contribute to factors with direct economic benefits, such as farmland irrigation, energy supply, flood control and reservoir fisheries (Grill et al. 2019), but affect freshwater ecosystems by inducing alteration of local hydrology (Timpe and Kaplan 2017), deterioration of water quality (Thompson et al. 2020), degradation of ecological connectivity (Kuriqi et al. 2021), loss of biological diversity (Granzotti et al. 2018), and habitat fragmentation (Barbarossa et al. 2020) of freshwater species. Among all aquatic organisms, the habitat fragmentation impact caused by damming may be most significant for freshwater fishes, as dams block their migration routes and limit their dispersal capacity and habitat connectivity (Benejam et al. 2016, Carvajal-Quintero et al. 2017, Puijenbroek et al. 2019, affecting the composition of fish communities and fish stock; thus, freshwater fish biodiversity is being threatened by an increasing number of hydropower facilities. ...
Environmental DNA methods have emerged as a promising tool in fish diversity studies and fishery management in various aquatic ecosystems. However, eDNA metabarcoding of fish communities in small hydropower dam reservoirs has received limited attention. In this study, we tested whether eDNA metabarcoding was an appropriate approach for the characterization of fish communities and fishery stock assessment by comparing its results with combined capture-based fishing methods and hydroacoustic surveys, which involved species detection and abundance/biomass evaluation. Our results indicated that the species detection performance of eDNA metabarcoding was basically similar to that of traditional capture-based fishing gear. However, it was also noteworthy that the eDNA method failed to cover all species detected by capture-based method, although some additional species were found. Besides, although we observed a significant correlation between site occurrence and sequence abundance for fishes, an effort to quantitatively establish a correlation between eDNA sequence counts and fish abundance/biomass was unsuccessful. Therefore, our study suggested that eDNA metabarcoding was an important supplementary tool to traditional capture-based fishing methods for the investigation and biomonitoring of fish diversity in small hydropower dam reservoirs. Further studies on the mechanisms of eDNA production, persistence, transportation and degradation in reservoirs might facilitate the interpretation of fish abundance and biomass from eDNA data.
... Consequently, information on the life history characteristics of Mediterranean brown trout populations is still limited, and only some ecological data are available (e.g., Champigneulle et al. 2003;Larios-López et al. 2015;Aparicio et al. 2018;Rocaspana et al. 2019). Mediterranean brown trout populations are currently declining mainly due to habitat degradation (Benejam et al. 2016), overfishing, and hybridization with non-native trout of the Atlantic lineage (Berrebi et al. 2000;Aparicio et al. 2005). In addition, an increase in water temperature due to climate change is likely to reduce its distributional range (Almodóvar et al. 2012). ...
The Mediterranean brown trout (Salmo trutta complex) is native to basins draining to the Western Mediterranean Sea, and natural populations are currently declining in abundance and distribution due to habitat degradation and introgression with stocked trout of the Atlantic lineage. Data on its life history traits are limited, although is an essential first step in developing effective conservation and management strategies. We studied age, growth and reproduction of Mediterranean brown trout from three headwater streams in northeast Iberian Peninsula. The maximum observed fork length was 382 mm in males and 322 mm in females, and six age groups (from 1+ to 6+) were identified. There was large variation in the back-calculated lengths for individual fish within ages. The von Bertalanffy growth curves were similar among streams and comparable to other European populations from small streams, but growth rate was lower when compared to larger and more productive rivers. Overall, sexual maturation began at age 1+, and the estimated L50 was 136 mm for males and 150 mm for females. Monthly variations in the gonadosomatic index showed that spawning occurred between late autumn and early winter, mainly in November and December. Mean fecundity and egg diameter were positively correlated with fish length, and values were within the typical range reported in other brown trout populations. Most of the differences among streams can be explained by differences in water temperature. These results constitute a contribution to better understanding of key aspects of Mediterranean brown trout biology, and to develop conservation and management strategies for preserving their populations.
Sharedit link: https://rdcu.be/cJQzS
... Water diversion affects river biota and processes. It reduces biofilm biomass and activity (Arroita et al., 2017), affects the storage of organic matter (OM) (Death et al., 2009;Arroita et al., 2015;Riis et al., 2017), reduces leaf-litter decomposition (Schlief and Mutz, 2009;Martínez et al., 2017), and modifies invertebrate (Dewson et al., 2007;Walters, 2011;González et al., 2018;González and Elosegi, 2021) and fish communities (Anderson et al., 2015;Benejam et al., 2016). These impacts probably are stronger during base flows, when a larger fraction of the water is diverted, but legacy effects from diversion periods can also affect the river during shutdown periods (Arroita et al., 2018). ...
Rivers are severely affected by human activities and many are simultaneously impacted by multiple stressors. Water diversion for hydropower generation affects ecosystem functioning of the bypassed reaches, which can alternate between periods with natural discharge and others with reduced flow that increase the surface of dry riverbeds. In parallel, urban pollution contributes a complex mixture of nutrients, organic matter, heavy metals, pesticides, and drugs, thus becoming an important stressor in rivers. However, there is little information on the interaction between both stressors on ecosystem functioning and, particularly, on organic matter processing, a key process linked to the input of energy to food webs. To assess the impact of water diversion and urban pollution on organic matter processing, we selected four rivers in a pollution gradient with a similar diversion scheme and compared reaches upstream and downstream from the diversion weirs. We measured leaf-litter decomposition and carbon dioxide (CO2) fluxes in both the wet channel and the dry riverbed. Water diversion and pollution in the wet channel did not affect CO2 fluxes but reduced microbial decomposition, whereas in the dry riverbed, their interaction reduced total and microbial decomposition and CO2 fluxes. Thus, both stressors affected organic matter processing stronger in dry riverbeds than in the wet channel. These results show that dry riverbeds must be taken into account to assess and manage the impacts of human activities on river ecosystems.
... In the last decade, more attention has been paid to the ecological impacts induced by SHPs, such as hydrological alteration [4][5][6], river connectivity fragmentation [7], habitat losses [8], and changes in species composition [9,10]. Research has also highlighted the cumulative impacts of SHPs to gain a better understanding of their environmental consequences [11][12][13]. ...
Releasing environmental flows is a valuable strategy for mitigating negative impacts of small-scale hydropower projects on river and riparian ecosystems. However, maintaining environmental flows has faced considerable resistance from different stakeholders, and previous studies have failed to appropriately investigate solutions. Here, online questionnaires and interviews were conducted among small-scale hydropower project owners, government administrators, and the public in Fujian Province, China. The results showed that the major hindrance to implementing environmental flows was the potential economic loss resulting from reductions in electricity production, stakeholders’ skepticism, technical difficulties, and a lack of the government supervision. Diversion-type projects pose the largest losses of electricity production after the release of environmental flows, and by adopting a 10% of mean annual flow as minimum target, most small-scale hydropower projects obtain low marginal profits without compensation. Here, we proposed an appropriate payment for ecosystem services by introducing an economic compensation program for different types of small-scale hydropower projects scaled by potential losses in electricity generation. Under such a scheme, economic losses from a reduction in electricity production are covered by the government, hydropower project owners, and electricity consumers. Our study offers recommendations for policymakers, officials, and researchers for conflict mitigation when implementing environmental flows.
... weirs, power plants and culverts) or consumptive water use can cause (i) interruption or prevention of movement and migration of aquatic organisms and (ii) habitat change or degradation. The consequences are manifold(Benejam et al., 2016). The lack of access to adequate spawning grounds can have a negative impact on the reproductive success and the stability of populations(Gosset et al., 2006;Johnsen et al., 2011). ...
Atlantic salmon Salmo salar L. and brown trout Salmo trutta fario L. are species of high socio-economic and ecological value. Declining populations make them target species of fisheries management. This paper reviews the direct effects of deficient longitudinal connectivity, changes in discharge, high water temperatures, oxygen depletion, changes in water chemistry and increasing loads of fine sediment on the critical life stages of spawning, egg incubation and emergence. It further provides an overview about the basic autecological requirements of Atlantic salmon and brown trout and summarises important thresholds of physico-chemical tolerances. This collection of information provides important baselines for assessing historical, ongoing and new threats relevant for the management of both species in fresh waters. Critical early-life stages of both species are almost identical, creating synergies in conservation and restoration. Seaward-migrating forms are exposed to further stressors, but improving starting conditions can also greatly improve their resilience.
... The impact of hydropower on river ecosystems depends largely on the water redistribution rule adopted to release environmental flows (Robson et al., 2011;Benejam et al., 2016;Gabbud and Lane, 2016). Typically, environmental flows correspond to a static redistribution rule determining a constant flow release (Minimal Flow Requirement, MFR, or Residual Flow), which is determined from the flow duration curve of the natural flow regime. ...
River regulation alters the natural flow regime of streams with consequent impacts on terrestrial and aquatic habitats of the riparian zone. The severity of such impacts can be modulated by changing the redistribution rules at water intakes and reservoirs. Contrary to minimal-flow policies, non-proportional and proportional redistribution policies result in variable environmental flow releases, namely Dynamic Environmental Flows (DEFs), which improve the global (i.e., ecological and economic) efficiency of water use practice, e.g., for energy production. DEF assessment is based on different indicators. However, the choice and aggregation method of different hydrological and fish habitat indicators affects the assessment of the global power plant performance, i.e., the Frontier of efficient solutions (sensu Pareto). This study investigates DEF assessment, and shows the extent to which the choice and method of aggregation of different indicators impacts the Frontier of Pareto-efficient solutions. The findings are supported by six case studies of hydropower practice that differ in terms of river morphology, energy production amount and technique. The relative importance of several types of indicators is examined as is their influence on optimal and sustainable water allocation solutions that lie on the Pareto Frontier. The analysis shows that DEFs arising from either proportional or non-proportional redistribution rules can positively impact strategies of sustainable management of freshwater resources.
... Among these, dams have been highlighted as the major threat to freshwater biodiversity at the global scale and can serve as a quantifiable indicator to present the impact of human activities on the longitudinal connectivity of rivers (Vörösmarty et al., 2010;Grill et al., 2019). To date, efforts to quantify dam impacts on longitudinal river connectivity (LRC) have been carried out worldwide (Benejam et al., 2016;Carvajal-Quintero et al., 2017;Van Puijenbroek et al., 2019). However, studies involving the systematic assessment of the longitudinal connectivity of China's large river systems are very limited, especially those reflecting the changing trends over the past 60 years. ...
Dams have reduced longitudinal river connectivity (LRC) worldwide, impairing habitat and migration opportunities for many freshwater fish species. However, national assessments linking LRC and threatened inland fish species distributions are lacking. Here, we show the trends in the LRC in China over the past 60 years, and quantitatively analyse their implications for threatened inland fish species. The average LRC in China decreased from 93.5% in 1960 to 25.1% in 2018, and the significant deterioration in LRC occurred over the last 20 years. Water resource regions with a high number of threatened fish species are concentrated in southern China, and the degree of threat to inland fish species increases with a decreasing average LRC. A total of 125 inland fish species are threatened by habitat degradation and loss, which is mainly caused by the construction of dams. Intrinsic factors and pollution are two other key threats to fish species in addition to the reduction of LRC. The results of this study can help us better understand the trends in LRC in China and their implications for inland fishes. Meanwhile, this study provides guidance for river management to help preserve biological diversity, including enhancing management of natural reserve areas, establishing ecological compensation mechanisms, preventing biological invasion, and monitoring and evaluation of restoration efforts.
Water diversion for hydropower plants is one of the leading causes of habitat alteration and biotic homogenization. The impacts of small hydropower plants on fish communities are usually assessed using taxonomic composition and structure indicators. Size-based indicators are useful tools to evaluate the effects of environmental factors and anthropogenic perturbations on riverine ecosystems. In this study, we investigated the impact of water diversion on fish community body size structure in 16 small hydropower plants in the upper Ter River basin (NE Iberian Peninsula). We tested the use of multiple size-based metrics under different sampling intensities (one- vs. four-pass electrofishing) and compared control vs. diverted stream stretches. Results revealed that water diversion had a negative effect on fish community average and median length, while size spectrum and size diversity metrics showed no responses to the impact. Altitude was positively related with body size metrics and was the strongest natural driver affecting them. Moreover, we found that all the size-based metrics exhibited consistent values under different sampling efforts. Our findings suggest that size-based metrics could be useful indicators for bioassessment of river flow alteration and that one-pass electrofishing was robust enough to characterize the stream fish community size structure in our study.
Los ríos temporales (RTs) son ecosistemas fluviales en los que los efectos de las perturbaciones antrópicas se mezclan con los de la propia perturbación natural que impone la temporalidad del flujo. A pesar de los avances en el conocimiento de los RTs, todavía persisten muchas lagunas de conocimiento que limitan el desarrollo de metodologías adecuadas para la evaluación de su estado ecológico. En esta revisión identificamos los retos actuales para la correcta evaluación del estado ecológico de los RTs y analizamos las oportunidades existentes para hacerles frente. Estos retos se centran en: la diferenciación entre RTs naturales o hidrológicamente impactados, la diferenciación entre perturbaciones naturales y antrópicas, el desarrollo de índices biológicos para pozas desconectadas y cauces secos, la adaptación de los índices hidrogeomorfológicos, y la aplicación de la teoría de metacomunidades en RTs. Las oportunidades están relacionadas con: el uso de nuevas herramientas moleculares, la existencia de índices alternativos a los tradicionales, la disponibilidad de datos para poder hacer modelización, y la implicación social en la evaluación del estado hidrológico y ecológico. La revisión se centra mayoritariamente en el conocimiento científico y de gestión acumulado desde la implementación de la DMA en España, pero recoge experiencias en otros RTs del mundo para guiar acciones de conservación y gestión en estos ecosistemas únicos y altamente amenazados por el cambio global.
In Spain, the largest inter-basin transfer is between the Tagus and Segura Basins. This transfer affects the regimes of the Mundo River, a tributary, and the Segura River. In this study, we examine two methodologies for the calculation of environmental flow regimes for the stretches affected by this alteration. When several methodologies are used to determine environmental flows, difficulty arises in deciding which values to propose to restore the river system hydrologically. This work tries to overcome this problem because we present a proposal to make them complementary. As a method for establishing the validity of minimum flow results, a simulation has been carried out on the river section, which has made it possible to evaluate the habitat created and the possibility of fauna movement. The results obtained by the habitat simulation method exceeded those obtained by hydrological methods in terms of habitat creation and hydraulic conditions for connectivity. These same tests have been used to assess the minimum official proposal made by the water administration.
HIGHLIGHTS
A procedure has been established that allows different results of ecological minimum flow values to be used in a complementary way to improve fish habitat.;
When results obtained by several methodologies are used in a complementary way, a more robust ecological flow regime proposal can be made.;
The method used can be applied together with other restoration measures in river stretches with strong morphological alterations.;
The construction of fish passage facilities is a promising approach to balance fish conservation and water resource development by improving river connectivity. To be successful, a fishway must efficiently attract fish to its entrance and have an interior flow field that meets the needs of migrating fish. In this paper, methods were explored to improve the efficiency of fishway passages by optimizing the flow field near the fishway entrance and the flow field inside the fishway in a case study at the Niuling Reservoir in the lower Yangtze River basin. The original engineering design was modified by designing a unique retaining wall with a notch to shape the appropriate flow pattern near the fishway entrance. The new wall optimized the flow field near the fish entrance to meet the hydraulic demands of target fishes under three operating scenarios, and the area of the suitable velocity zone increased by 48.79%, 12.71%, and 4.06% in scenarios 1 through 3, respectively. The original vertical slot fishway was modified with a sill to optimize the flow field inside the fishway. The optimized fishway design scheme reduced the main flow velocity inside the fishway to a large extent, and the maximum flow velocity in the upstream and downstream sections of the fishway decreased by 0.10 m/s and 0.09 m/s on average, respectively. The results of this study provide an important reference for the construction and optimization of fish passage facilities and have great significance for fish migration and biological diversity.
Researchers worldwide are increasingly concerned about the loss of longitudinal river connectivity. Here, we determined how the construction of serial weirs influences the nutrient regime, organic matter, solids deposition, water flow, and general water chemistry in a natural river during 2017–2021. The results indicated that the monsoon rainfall intensity primarily governed the seasonal water-quality trends. Downriver weirs were more affected than upriver weirs, highlighting the significance of water residence time (WRT). The total phosphorus (TP) showed a strong positive relationship with inflow (R2 = 0.847), outflow (R2 = 0.845), and WRT (R2 = 0.734). However, total suspended solids (TSS) had a lesser effect than TP, i.e., inflow (R2 = 0.62), outflow (R2 = 0.61), and WRT (R2 = 0.541). The sestonic Chl-α showed significant spatial variation year-round, e.g., Chl-α was < 25 µg·L−1 in up- and midriver weirs and > 25 µg·L−1 in downriver weirs pre-monsoon. A monsoon dilution effect on Chl-α was observed during intensive rainfall, further augmenting the weir impact. The principal component analysis yielded a 76.016% cumulative variance. The chemical health status was ‘fair’ in the upriver and ‘poor’ in the downriver gradients. In conclusion, sestonic Chl-a, WRT, chemical health, and inflow along the river gradient were interlinked, indicating an evident effect of weir installation on river water quality. The weirs significantly harmed the river’s lotic properties, causing it to morph into a lotic-lentic environment. Water-quality degradation was reflected in three river zones (up-, mid-, and downriver), indicative of the impact of weir installation.
In most countries, major development projects must satisfy an Environmental Impact Assessment (EIA) process that considers positive and negative aspects to determine if it meets environmental standards and appropriately mitigates or offsets negative impacts on the values being considered. The benefits of before-after-control-impact monitoring designs have been widely known for more than 30 years, but most development assessments fail to effectively link pre- and post-development monitoring in a meaningful way. Fish are a common component of EIA evaluation for both socioeconomic and scientific reasons. The Ecosystem Services (ES) concept was developed to describe the ecosystem attributes that benefit humans, and it offers the opportunity to develop a framework for EIA that is centred around the needs of and benefits from fish. Focusing an environmental monitoring framework on the critical needs of fish could serve to better align risk, development, and monitoring assessment processes. We define the ES that fish provide in the context of two common ES frameworks. To allow for linkages between environmental assessment and the ES concept, we describe critical ecosystem functions from a fish perspective to highlight potential monitoring targets that relate to fish abundance, diversity, health, and habitat. Finally, we suggest how this framing of a monitoring process can be used to better align aquatic monitoring programs across pre-development, development, and post-operational monitoring programs.
On the impact of small hydropower plants on Natura 2000 sites and water bodies in Romania.
Aim This study verified if the macrophyte banks found in two reservoirs of small hydroelectric plants (SHPs) have a functional ecological role for the initial development of ichthyofauna. Additionally, we compared the differences in the structure of the fish assemblages along each reservoir compartment and between reservoirs. Methods Sampling was performed in March 2018, in lotic, intermediate, and lentic compartments of Palmeiras and Retiro reservoirs, Sapucaí-Mirim River (SP). Three distinct macrophyte banks in each stretch (triplicates), considering the most representative in terms of composition (recurrency/dominance), were sampled, resulting in 18 samples (nine per reservoir). For fish collection we used a sieve of 1 m2 of area, mesh size of 1 mm, which was manually hauled, from the boat, in the marginal aquatic vegetation (three hauls per sample). Simultaneously, we measured basic limnological parameters with a Horiba U-52 water probe, adjacent to the banks. Results The presence of juveniles of all fish orders found in the river, Characiformes, Siluriformes, Synbranchiformes, Gymnotiformes and Cichliformes, demonstrates that, at least in certain moment of their development cycle, the macrophyte banks are used by species with different ecological requirements. It was observed significant statistical differences in the structure of the ichthyofauna along the longitudinal axes of the reservoirs, but not between reservoirs. The same was seen for the limnological data (PCA). Conclusions The macrophyte banks found in the SHPs reservoirs have a potential role as nurseries for the local ichthyofauna, mainly, but not exclusively, for sedentary species and with parental care. This association is ecologically relevant, given the absence of typical lateral habitats for the initial development of the fish fauna. Additionally, despite the reservoirs small size, spatial organization was also important for the assemblage’s structure, with differences in terms of composition, size and development stages along the distinct sampling stretches.
The implementation of vertical slot fishway (VSF) has been demonstrated to be an effective mitigation measure to alleviate extensive river fragmentation by artificial hydraulic structures such as weirs and dams. However, non-suitable flow velocity and turbulent kinetic energy significantly affect fish swimming behavior and, as a result, hinder such facilities' performance. Therefore, this study's main objective is to propose a new configuration of VSF that can allow the passage of different fish species under frequent variations of flow discharge. To achieve that objective several novel configurations of VSF were numerically investigated using the FLOW-3D® model. Namely, five variants of angles between baffles, four different pool widths, and another upgraded version of VSF by introducing cylindrical elements positioned after the opening behind the baffles were tested. Results show that smaller angles between baffles increase the Vmax and decrease the maximum turbulent kinetic energy (TKEmax); the opposite result was obtained when increasing angles between baffles. Namely, the Vmax was increased up to 17.9% for α=0° and decreased up to 20.37% for α = 37°, in contrast, TKEmax decreased up to −20% for α = 0° and increased up to 26.5% for α = 37°. Narrowing the pool width increased the Vmax linearly; nevertheless, it did not significantly affect the TKEmax as the maximum difference was only +3.5%. Using cylinders with a large diameter decreased the Vmax and increased TKEmax; in contrast, using cylinders with smaller diameters further reduces the Vmax velocity inside the pool while increasing the TKEmax. However, in the case of cylinders, the dimension of the recirculation depended on the configuration and arrangement of the cylinder within the pool. Overall, the maximum velocity was reached at near 77% of the water depth in all cases. Finally, solution-oriented findings resulted from this study would help water engineers to design cost-effective VSF fishways to support the sustainable development of hydraulic structures while preserving aquatic biodiversity.
Electricity production by hydropower is negatively affected by drought. To understand and quantify risks of less than normal streamflow for hydroelectricity production (HP) at the global scale, we developed an HP model that simulates time series of monthly HP worldwide and thus enables analyzing the impact of drought on HP. The HP model is based on a new global hydropower database (GHD), containing 8,716 geo-localized plant records, and on monthly streamflow values computed by the global hydrological model WaterGAP with a spatial resolution of 0.5°. The GHD includes 44 attributes and covers 91.8% of the globally installed capacity. The HP model can reproduce HP trends, seasonality, and interannual variability that was caused by both (de)commissioning of hydropower plants and hydrological variability. It can also simulate streamflow drought and its impact on HP reasonably well. Global risk maps of HP reduction were generated for both 0.5° grid cells and countries, revealing that 67 out of the 134 countries with hydropower suffer, in 1 out of 10 years, from a reduction of more than 20% of mean annual HP and 18 countries from a reduction of more than 40%. The developed HP model enables advanced assessments of drought impacts on hydroelectricity at national to international levels.
Fish pass assessment in the rivers of Catalonia (NE Iberian Peninsula). A case study of weirs associated with hydropower plants and gauging stations This study evaluated the effectiveness of fish passes in Catalan rivers (NE Iberian Peninsula). The aim was to test current functionality to enhance these structures for the purpose of optimising their management. We analysed river connectivity and fish pass facilities to generate information to improve the design, construction, management and assessment of solutions related to fish passage in Catalan rivers according to international best practices. In 2006, a preliminary evaluation of the locations and effectiveness of fish pass facilities in Catalonia was conducted through direct inspection of 78 fishways. Most of them were retro-fitted solutions using broad-spectrum technical structures, mainly pool fishway or pool pass facilities. An analysis of the effectiveness of 7 of the new fish passes (4, 2 and 1 passes in the Ter, Ebro and Tordera rivers, respectively) was performed between 2006 and 2009. The fish passes were located in weirs associated with hydropower plants and gauging stations. Our preliminary assessment of fish connectivity was based on a field visit and collection of information to populate a database of existing obstacles and associated fishways and calculation of the new version of the ICF index (river connectivity index) for all of them. Several methodologies were used to check the effectiveness of a selection of fish pass solutions, most of which were based on passage rates directly or indirectly estimated for each species. Direct estimation techniques involved the installation of fish traps upstream of the facility at the exit of the fish pass and visual counts. Indirect estimation techniques compared the fish population structure on each side of the obstacle in river sections with equivalent hydrology and habitat characteristics using electric fishing or trapping systems, group mark-recapture methods and individual mark-recapture methods (PIT tags). The results showed that (1) existing solutions to improve fish migration in Catalonia are insufficient (only present at approximately 8% of obstacles), and where they do exist, the fish passes are usually inadequate or poorly maintained. (2) Fish passes are generally inadequate or insufficient for the total native fish fauna from each water body. Additionally, with few exceptions, fish passage rates are too low, and in most cases, only fish with a high capacity to overcome obstacles or the largest individuals succeed in migrating. (3) Fish pass effectiveness agrees with the results of the new version of the ICF index. RESUMEN Evaluación de dispositivos de paso para peces en los ríos de Catalunya (NE de la Península Ibérica). Estudio del caso de azudes asociados con plantas hidroeléctricas y estaciones de aforo Este estudio evalua la eficacia de dispositivos o soluciones de paso para peces en los ríos de Catalunya (NE de la Península Ibérica). Se realizó con el propósito de comprobar su funcionalidad actual y también para poder mejorar elementos constructivos y/o para optimizar aspectos de gestión. El objetivo del estudio era analizar la conectividad de los ecosistemas fluviales y generar información para mejorar el diseño , construcción , gestión y evaluación de soluciones para el paso de peces
RESUMEN La evolución de la energía hidroeléctrica en España en las últimas décadas ha sido siempre creciente, aunque la participación de ésta en el total de eléctrica producida ha ido disminuyendo. Las modernas tecnologías de regulación y control han aumentado la eficiencia de las centrales y del aprovechamiento del recurso agua. Palabras clave: agua, energía, hidroelectricidad, España. ABSTRACT The evolution of the hydroelectric power in Spain during the last decades has always been increasing, though its proportion with respect to the total of produced electricity has been diminishing. The modern technologies of regulation and control have increased the efficiency of the hydroelectric industries and of the utilization of the water resources.
Recently, Minto et al. (2008), based on a fishery data set including marine, estuarine, and freshwater fishes, described higher variability in the survival rates of juveniles at low rather than at high parental density in an inversely density-dependent fashion and suggested density-dependent mechanisms underpinning those patterns. This study, based on a long-term study of brown trout (Salmo trutta; a species and habitat not included in the Minto et al. (2008) analysis), documents that survival rates in these stream-living populations exhibit a pattern that matches exactly those reported by Minto et al. (2008). Nevertheless, hypothesis testing rejected the occurrence of stock–recruitment relationships and the operation of density-dependent recruitment regulation. The patterns elucidated for these brown trout populations can be entirely explained by the operation of two single environmental factors, namely, stream discharge in March determining annual survival rates across streams and sites and site-specific depth determining site-specific survival rates. It is open to question that exactly the same patterns can be generated by two sets of opposing factors, density-dependent (i.e., Minto et al. 2008) and environmental factors (i.e., this study). The consistency of this pattern suggests that survival rates and recruitment are probably determined by environmental factors across fish populations and habitats.
A small hydroelectric power station was built in 1993 on the River Hoz Seca (Tagus basin, central Spain). Pre- and post-regulation studies provided the opportunity to test the early effects of this disturbance on the brown trout Salmo trutta L. population. Before and after comparisons of population density and biomass, age composition, growth and production were made upstream and downstream of the diversion dam. The effects of disturbance on benthic macroinvertebrates were also analysed but no changes in abundance were detected. The downstream estimated population densities and biomass of trout showed a decrease of about 50 and 43%, respectively, following regulation. Examination of length-for-age tables revealed no obvious change in growth but a significant difference in age structure. The main consequence of the imposed fluctuating flow regime was a serious reduction in trout production caused by a loss of suitable habitat and a loss of juveniles. Copyright © 1999 John Wiley & Sons, Ltd.
Long-term discharge records (17-81 yr) of 78 streams from across the continental USA were analyzed. Based on overall flow variability, flood regime patterns and extent of intermittency, 11 summary statistics were derived from the entire record for each stream. Using a nonhierarchical clustering technique, 9 stream types were identified: harsh intermittent, intermittent flashy, intermittent runoff, perennial flashy, perennial runoff, snowmelt, snow + rain, winter rain, and mesic groundwater. Stream groups separated primarily on combined measures of intermittency, flood frequency, flood predictability, and overall flow predictability, and they showed reasonable geographic affiliation. The positions of the streams in a continuous three-dimensional flow space illustrate the wide range of ecologically important hydrologic variability that can constrain ecological and evolutionary processes in streams. -from Authors
Alterations to the natural flow regime affect the structure and function of rivers and wetlands and contribute to loss of biodiversity worldwide. Although the effects of flow regulation have been relatively well studied, a lack of synthesis of the ecological consequences of low flows and droughts impedes research progress and our grasp of the mechanistic effects of human-induced water reductions on riverine ecosystems. We identified 6 ecologically relevant hydrological attributes of low flow (antecedent conditions, duration, magnitude, timing and seasonality, rate of change, and frequency) that act within the temporal hierarchy of the flow regime and a spatial context. We synthesized the literature to propose 4 principles that outline the mechanistic links between these low-flow attributes and the processes and patterns within riverine ecosystems. First, low flows control the extent of physical aquatic habitat, thereby affecting the composition of biota, trophic structure, and carrying capacity. Second, low flows mediate changes in habitat conditions and water quality, which in turn, drive patterns of distribution and recruitment of biota. Third, low flows affect sources and exchange of material and energy in riverine ecosystems, thereby affecting ecosystem production and biotic composition. Last, low flows restrict connectivity and diversity of habitat, thereby increasing the importance of refugia and driving multiscale patterns in biotic diversity. These principles do not operate in isolation, and many of the ecological pathways that are affected by low flows are likely to overlap or occur simultaneously, potentially resulting in synergistic and complex effects. Last, we outlined major human-induced threats to low-flow hydrology and how they act upon the ecologically relevant hydrological attributes of low flow to affect potential changes in riverine ecosystem integrity. The mechanistic links described in this synthesis can be used to develop and test hypotheses of low-flow hydrological–ecological response relationships in a cause–effect framework that will have value for both research and river flow management. Continued experimental research and ongoing consolidation of ecological information will improve our understanding and ability to predict consequences of low-flow alteration on river, floodplain, and estuarine ecosystems.
Nonnative brook trout Salvelinus fontinalis are abundant in Pine Creek and its main tributary, Bogard Spring Creek, California. These creeks historically provided the most spawning and rearing habitat for endemic Eagle Lake rainbow trout Oncorhynchus mykiss aquilarum. Three-pass electrofishing removal was conducted in 2007–2009 over the entire 2.8-km length of Bogard Spring Creek to determine whether brook trout removal was a feasible restoration tool and to document the life history characteristics of brook trout in a California meadow stream. After the first 2 years of removal, brook trout density and biomass were severely reduced from 15,803 to 1,192 fish/ha and from 277 to 31 kg/ha, respectively. Average removal efficiency was 92–97%, and most of the remaining fish were removed in the third year. The lack of a decrease in age-0 brook trout abundance between 2007 and 2008 after the removal of more than 4,000 adults in 2007 suggests compensatory reproduction of mature fish that survived and higher survival of age-0 fish. However, recruitment was greatly reduced after 2 years of removal and is likely to be even more depressed after the third year of removal assuming that immigration of fish from outside the creek continues to be minimal. Brook trout condition, growth, and fecundity indicated a stunted population at the start of the study, but all three features increased significantly every year, demonstrating compensatory effects. Although highly labor intensive, the use of electrofishing to eradicate brook trout may be feasible in Bogard Spring Creek and similar small streams if removal and monitoring are continued annually and if other control measures (e.g., construction of barriers) are implemented. Our evidence shows that if brook trout control measures continue and if only Eagle Lake rainbow trout are allowed access to the creek, then a self-sustaining population of Eagle Lake rainbow trout can become reestablished.
a b s t r a c t We describe a tolerance classification based on the physicochemical parameters of water and habitat quality indices for native and introduced fish species in northeastern Spain. Although fish are widely used as biological indicators, the tolerance categories currently available for Spanish Mediterranean fish species are uncertain or subjective. We sampled 430 sites covering a wide range of river conditions, allowing us to develop tolerance scores based on a quantitative assessment. We used indirect ordina-tion methods to establish stress gradients between the environmental variables compiled during the monitoring surveys carried out from 2002 to 2008. We then drew up a tolerance classification for the most common species in our dataset using weighted average inference models based on the following gradients: water quality and the state of physical habitat. The results were corroborated by multivariate gradient analysis. The fish scores obtained were applied to an independent dataset and a positive corre-lation was found between assessment protocols. Our results corroborate the use of fish, including exotic fish species, as biological indicators. Our findings may be used in a regional Index of Biotic Integrity and for the use of fish in bioassessment studies based on scores.
The Three-Georges Dam holds many records in the history of engineering.
While the dam has produced benefits in terms of flood control,
hydropower generation and increased navigation capacity of the Yangtze
River, serious questions have been raised concerning its impact on both
upstream and downstream ecosystems. It has been suggested that the dam
operation intensifies the extremes of wet and dry conditions in the
downstream Poyang Lake, and affects adversely important local wetlands.
A floodgate has been proposed to maintain the lake water level by
controlling the flow between the Poyang Lake and Yangtze River. Using
extensive hydrological data and generalized linear statistical models,
we demonstrated that the dam operation induces major changes in the
downstream river discharge near the dam, including an average
“water loss”. The analysis also revealed considerable
effects on the Poyang Lake water level, particularly a reduced level
over the dry period from late summer to autumn. However, the dam impact
needs to be further assessed based on long-term monitoring of the lake
ecosystem, covering a wide range of parameters related to hydrological
and hydraulic characteristics of the lake, water quality,
geomorphological characteristics, aquatic biota and their habitat,
wetland vegetation and associated fauna.
The age structure, growth and reproduction of Barbus sclateri in a non-regulated section of the Segura River were similar to previously studied populations of undisturbed areas. Differences in the duration of the growth period or the reproductive cycle are considered evidence of the plasticity of the species as it adapts to different latitudes and local habitat characteristics. However, this population differed from one in a section with artificial water flow regulation. The non-regulated river population had a greater number of age groups, displayed a regular condition cycle, reached maturity earlier at lower ages and lengths and showed greater fecundity than the regulated river population. The mean lengths at age were longer in the regulated river population, possibly owing to the longer river section studied and/or to selective mortality of smaller specimens within a particular age group from the high water velocity when sluices are opened.
The concentrations of Zn, Cu, and Cd in the interrenal tissue and liver of yellow perch, Perca flavescens, sampled in six lakes in the mining region of Abitibi (Quebec) revealed a gradient of contamination: Reference lakes, intermediate-contaminated lakes, and highly contaminated lakes. Interrenal and hepatic metallothionein concentrations followed a similar gradient, and there was a strong relationship between metallothionein and total metal (Zn + Cu + Cd) content in the liver and Cu + Cd content in the interrenals. Following a standardized confinement stress test, plasma cortisol and glucose were significantly higher in fish from reference lakes compared with the two most contaminated lakes. No differences in plasma chloride were observed. The secretory response of the interrenal tissue to in vitro stimulation by adrenocorticotropic hormone and dibutyryl cyclic AMP was significantly lower in fish from a contaminated lake compared with fish from a reference lake. Condition factor was significantly lower in yellow perch from the most contaminated lakes. This study demonstrated that a chronic field exposure to base metals increases hepatic and interrenal tissue metallothionein concentrations and disrupts the physiological capacity of yellow perch to generate the normal hormonal stress response.
Regression relations which describe the density of mammalian populations as functions of adult body mass were built using data for carnivores and herbivores from 4 continents. Global and temperate relations are similar to previous descriptions: herbivores are more abundant than carnivores and population density declines as body size increases. Regressions within biogeographic regions support this pattern but depart in detail. North American species are more abundant than tropical species and species from tropical America and central Africa are more abundant than mammals from East Africa and southern Asia. Within regions, herbivore density is less affected by size and presumably more affected by other factors than the global regressions would suggest. Although the general regressions explain c70% of the variance in animal density, more geographically-restricted relations are less successful and none of the regressions are effective tools for the prediction of the abundance of individual populations. However, the mean tendency of population density described by these regressions can be of use in depicting the probable role of different-sized mammals in community structure and dynamics. -Authors
The health or fitness of fish populations in aquatic ecosystems can be assessed by a variety of criteria ranging from individual biochemical and physiological measures to population level attributes such as growth, reproductive success, or year-class strength. Lipid storage and dynamics within the organism, however, are a particular important attribute of fish health and future population success. Lipids are critical not only to the survival and fitness of individuals but also to the success of reproduction and recruitment of future year classes within the population. This chapter discusses four areas in which lipids play an important role in fish health including (1) overwinter starvation and survival, (2) energy allocation strategies, (3) reproductive performance and early life history. and (4) environmental stress.
Weight-length relationships were used as a simple method to test differences in condition between several populations of Mediterranean barbel and to examine possible correlations between fish condition and ecological factors. We analysed 14 populations of Mediterranean barbel from two basins with different ecological conditions. Statistical analysis (ANCOVA) showed that there were significant differences (P < 0.05) in condition between populations, which could imply differences in habitat characteristics. Oxygen availability and riparian cover seem to be the main ecological factors affecting the condition of this species in the area studied. Therefore, the condition of the Mediterranean barbel may be a good indicator of habitat quality in stream ecosystems.
Hydropower is a key source for renewable electricity generation and it has an important potential to be marketed as green energy. There has been a substantial increase in the number of hydroelectric power plants in recent years in Turkey. While offering ecological advantages from a global perspective, such as climate change mitigation, emergency management, and reduction of flooding risk, the operation and construction of hydroelectric power plants may cause some environmental impacts on the local and regional level. These include harm to fish populations, a loss of aquatic habitat, a significant change in natural flow regimes, and deterioration of the landscape. The article aims to suggest various ways to resolve these issues, and to research the problems of 24 hydroelectric power plants operated and constructed on dams, rivers, and canals by the State Hydraulic Works (DSI) or private sector in the Buyuk Menderes Basin and in the West Mediterranean Basins in Turkey.
A new approach for analysing morphometric data of reproductive cycles is proposed, involving multivariate analysis of covariance of the directly measured variables (e.g., total weight and gonadal weight), with body length being the covariate. Multivariate, univariate, and between-group tests can be used, progressively if significant differences have been found previously. Seasonal variation and other factors of interest can be described with predicted means of the model, adjusted for covariate, rendering the use of indices such as condition factor and gonadosomatic index unnecessary. A special design of multivariate analysis of covariance, with a pooled covariate by factor interaction, can be used to test the fundamental assumption of homogeneous slopes (parallelism hypothesis) in the standard multivariate analysis of covariance. Data for an Iberian brackish water cyprinodontid fish are used to demonstrate the proposed method.
The Marne reservoir (Der and Champaubert Lakes, 48 km2, 8 m mean depth) is one of the three major reservoirs constructed on the upper reaches of the Seine river to regulate its flow. The major features of the ecological functioning of the reservoir were analysed on the basis of results obtained in a 3-year routine sampling programme where the main variables of water quality were determined upstream, downstream and within the reservoir. Planktonic and benthic processes were also investigated in 1 year. A model of the reservoir was developed by coupling the RIVE model (which describes the major microbiological processes involved in the ecological functioning of aquatic systems), with a description of the morphology and hydrology of the reservoir. The model was used to simulate the seasonal and year-to-year variations of nutrients (N, P, Si) and phytoplankton biomass, and to compare them with the observed data. The model was then used to explore the effect of different control factors on denitrification, namely residence times and phosphorus loading. The results showed little influence on the absolute amount of nitrate denitrified within a realistic range of residence times and phosphorus loading. The Marne reservoir appears however to be a significant sink for nitrate (40% of the influx is eliminated), but this reduction represents only 10% of the nitrate flux at the outlet of the Marne sub-basin. Copyright © 2000 John Wiley & Sons, Ltd.