Large Hydropower Plants Research Articles

Equivalent circuit modelling of large hydropower plants with complex tailrace system for ultra-low frequency oscillation analysis

Focused on the hydraulic factor-induced ultra-low frequency oscillation phenomenon occurring in a large hydropower plant, this paper investigates the precise modelling of hydraulic transient characteristics in its complex tailrace system and reveals the feasible oscillation suppression schemes from the source side. Combining the telegraphist's equations with the Saint-Venant equations, the mathematical expression of equivalent circuit model (ECM) for open channels is deduced, thus to expand the utilization of ECM to hydraulic transients description in pressurized pipe and open channel combination systems and to establish the high-order equivalent circuit topology of the overall tailrace system in a real hydropower plant. Based on the mathematical model, the feasibility and effectiveness of two different oscillation suppression approaches involving increasing the hydraulic losses on the branch tailrace channels or the main tailrace channel, respectively, are discussed in detail via numerical simulation. Furthermore, the superiority of the oscillation suppression scheme involving increasing hydraulic losses in branch channels in reducing the extra power generation loss is demonstrated. The application of equivalent circuit theory in complex hydraulic systems can contribute to the mechanism-related research on ultra-low frequency oscillations in hydro-dominant power systems.

Operational characteristics and parameter sensitivity analysis of hydropower unit damping under ultra-low frequency oscillations

Hydropower is probably the largest sustainable energy source in use and plays an important role in maintaining power and frequency stability of the power system. However, in hydropower-dominated power systems (HDPS), hydropower units often exhibit negative damping, increasing the risk of ultra-low frequency oscillations (ULFO). In this paper, the operating characteristics and parameter sensitivities of hydropower unit (HPU) damping in an HDPS are investigated, taking a large hydropower plant in southwest China as an example. To this end, a refined mathematical model of a cluster of HPUs is established, and an improved damping quantification method and parameter sensitivity analysis indices are proposed for the complex energy system. On this basis, the damping of the HPU with different control modes under a ULFO is investigated with the change of operating conditions represented by guide vane opening, water head and the number of parallel-running units. Meanwhile, the sensitivity of the damping to the system parameters is analyzed to reveal the influence mechanism of the parameters on the ULFO. Also, measures to suppress the ULFO are formulated from two levels of operation and control combined with theoretical analysis.

Climate Change Effects on Fish Passability across a Rock Weir in a Mediterranean River

Climate change represents a major challenge for the management of native fish communities in Mediterranean rivers, as reductions in discharge may lead to a decrease in passability through small barriers such as weirs, both in temporary and perennial rivers. Through hydraulic modelling, we investigated how discharges from a large hydropower plant in the Tagus River are expected to affect the passability of native freshwater fish species through a rock weir (Pego, Portugal), equipped with a nature-like fish ramp. We considered not only mean daily discharge values retrieved from nearby gauging stations (1991–2005) for our flow datasets, but also predicted discharge values based on climatic projections (RCP) until the end of the century (2071–2100) for the Tagus River. Results showed that a minimum flow of 3 m3 s−1 may be required to ensure the passability of all species through the ramp and that passability was significantly lower in the RCP scenarios than in the historical scenario. This study suggests that climate change may reduce the passability of native fish species in weirs, meaning that the construction of small barriers in rivers should consider the decreases in discharge predicted from global change scenarios for the suitable management of fish populations.

Comprehensive approach to the strategy of low-carbon socio-economic development of Russia

The article discusses the key risks of implementing a strategy for long-term socio-economic development of Russia with a low level of greenhouse gas emissions. In recent years, the climate agenda has been the most important driver of structural shifts in the world economy and is viewed by leading countries as a factor in intensifying economic growth and consolidating their technological leadership at the global level. In this context, Russia’s efforts to reduce its carbon footprint without direct import of low-carbon technologies and equipment from developed countries will run into non-recognition (of the carbon sink by Russian forests and carbon-free nature of nuclear and large hydro power plants) and increase in requirements for even more radical reduction in emissions. At the same time, Russia is already making a significant contribution to achieving the goals of the Paris Agreement. The article provides a list of measures that should underlie a balanced national climate policy. The strategy for the socio-economic development of Russia with a low level of greenhouse gas emissions should provide for a balance between solving the problems of preserving the population, improving the quality of its life, and ensuring dynamic and inclusive economic growth in the country. Russia’s potential announcement of commitments to unequivocally achieve carbon neutrality by mid-century carries serious risks to national interests. Instead, a more flexible language should be used to strive for carbon neutrality.

How green can Amazon hydropower be? Net carbon emission from the largest hydropower plant in Amazonia.

The current resurgence of hydropower expansion toward tropical areas has been largely based on run-of-the-river (ROR) dams, which are claimed to have lower environmental impacts due to their smaller reservoirs. The Belo Monte dam was built in Eastern Amazonia and holds the largest installed capacity among ROR power plants worldwide. Here, we show that postdamming greenhouse gas (GHG) emissions in the Belo Monte area are up to three times higher than preimpoundment fluxes and equivalent to about 15 to 55 kg CO2eq MWh-1 Since per-area emissions in Amazonian reservoirs are significantly higher than global averages, reducing flooded areas and prioritizing the power density of hydropower plants seem to effectively reduce their carbon footprints. Nevertheless, total GHG emissions are substantial even from this leading-edge ROR power plant. This argues in favor of avoiding hydropower expansion in Amazonia regardless of the reservoir type.

Central Asian and Middle Eastern policy towards Tajikistan

The article analyzes the main policy directions towards Tajikistan, neighboring countries of Central Asia and culturally related to the Tajiks of the Middle East towards Tajikistan. The civil war in Tajikistan between supporters of the country’s secular and religious paths of development (1992-1997) caused mixed attitudes and policies on the part of various state, political and religious circles in Afghanistan. However, after it became clear that the struggle between secular and Islamist forces in Tajikistan could destroy the country as such, the culturally and linguistically close to the Tajiks political elite of Afghanistan (B. Rabbani and A. Masood) and Iran (A. Rafsanjani) made significant efforts to end the civil war in Tajikistan as mediators and expressed interest in the sustainable development of Tajikistan. In the 2000s, Iran abandoned attempts to influence Tajik policy in order to promote the establishment of a religious state in Tajikistan, turning to cooperation with the secular Tajik authorities in the economic sphere.
 Important issues complicating relations between Uzbekistan and Kyrgyzstan and Tajikistan are the construction by Tajiks of large hydropower plants on mountain rivers, which Uzbekistan considers a threat to national security, and unresolved border disputes, which are a source of constant aggravation in Kyrgyz-Tajik. In general, Tajikistan has complex problems of various kinds with most of its neighbors (with Afghanistan - drug trafficking and Islamic influences, with Uzbekistan - water energy, with Kyrgyzstan - border), which prevent bilateral relations to reach a new level of quality.

Cooperative operation of the Grand Ethiopian Renaissance Dam reduces Nile riverine floods

AbstractThe construction of the Grand Ethiopian Renaissance Dam (GERD) on the Nile River has triggered much debate between Ethiopia, Sudan, and Egypt on the dam's effects. Once completed, the GERD will be Africa's largest hydropower plant. This study analyzes the implications of cooperative long‐term operation of the GERD for Nile riverine flooding downstream of the dam. A daily river system model of the Eastern Nile is developed and used to examine how cooperative long‐term operation of the GERD would affect the occurrence of three flood alarm levels (alert, critical, and flooding) in Sudan downstream of the dam. A reconnaissance‐level flood inundation model is developed for the Nile within Khartoum State (Sudan's capital) to assess the GERD's impacts on the flood extent in the state based on simulated flows from the river system model. Assuming the GERD is operated to achieve a 90% power reliability and active upstream‐downstream data sharing between Ethiopia and Sudan on the dam's daily outflows, results show that the GERD would reduce the occurrence of the three alarm levels. Based on 34 simulated river flow sequences, the proportion of years with at least one flooding alarm day at Khartoum Gage declined from 37% without the GERD to 11% with the GERD. Seasonal coordination and planning between Ethiopia and Sudan are necessary to mitigate the remaining riverine flood hazard. Although cooperative long‐term operation of the GERD could play a positive role in reducing the riverine flood hazard in Sudan, the associated river flow alterations would adversely impact recession agriculture and the environment.

Integrated Impact Assessment for Sustainable Hydropower Planning in the Vjosa Catchment (Greece, Albania)

Mitigating climate change, while human population and economy are growing globally, requires a bold shift to renewable energy sources. Among renewables, hydropower is currently the most economic and efficient technique. However, due to a lack of impact assessments at the catchment scale in the planning process, the construction of hydropower plants (HPP) may have unexpected ecological, socioeconomic, and political ramifications in the short and in the long term. The Vjosa River, draining parts of Northern Greece and Albania, is one of the few predominantly free-flowing rivers left in Europe; at the same time its catchment is identified an important resource for future hydropower development. While current hydropower plants are located along tributaries, planned HPP would highly impact the free-flowing main stem. Taking the Vjosa catchment as a case study, the aim of this study was to develop a transferable impact assessment that ranks potential hydropower sites according to their projected impacts on a catchment scale. Therefore, we integrated established ecological, social, and economic indicators for all HPP planned in the river catchment, while considering their capacity, and developed a ranking method based on impact categories. For the Vjosa catchment, ten hydropower sites were ranked as very harmful to the environment as well as to society. A sensitivity analysis revealed that this ranking is dependent upon the selection of indicators. Small HPP showed higher cumulative impacts than large HPP, when normalized to capacity. This study empowers decision-makers to compare both the ranked impacts and the generated energy of planned dam projects at the catchment scale.

Temporary turbine and reservoir level management to improve downstream migration of juvenile salmon through a hydropower complex

Developing management rules to improve downstream migration of salmon smolts in large hydropower plants is essential to limit mortality and migration delay. A 2-year telemetry study was conducted to assess the efficiency of temporary measures to enhance the safety and speed of juvenile salmon passage through the Poutès dam (Allier River, France). 124 smolts were tracked through the reservoir and downstream of the dam, during implementation of turbine modulation and/or shutdown during night and reservoir level lowering. Level lowering significantly reduced median residence time from 3.4 days to 4.4 hours. However, even with high spill during turbine modulation, the risk of smolt being drawn toward the turbines was increased at low reservoir level due to the site's configuration, greater proximity to the surface and weak repulsive effect of the rack. Moreover, results revealed that a substantial proportion of smolts can migrate during daytime and twilight during floods, even at the beginning of the migration period. Thus targeted turbine shutdown has a good potential to protect smolts, but implementation requires studies taking account of site specificities and a flexible approach.

Overview of hydropower resources and development in Uganda

<abstract> <p>Even though hydropower plants are currently the most dominant source of electricity in Uganda, the rate of development of these resources for power generation remains low. Using a semi-systematic review approach, this paper seeks to understand why there is a slow rate of hydropower development in Uganda (challenges) and thereby provide potential solutions to these challenges. With current total capacity of about 1011 MW, findings indicate that there is a higher future prospect for hydropower generation in Uganda, with an estimated potential of over 4500 MW. In terms of number of projects, small-scale hydropower plants dominate power plants in Uganda, currently accounting for 19 out of 35 grid-connected power plants. However, with 855 MW installation capacity, large hydropower plants dominate the power generation plants landscape in Uganda. This study found that the challenges to hydropower development in this country are multi-dimensional including technical, economic, environmental, and social factors, and shows that the cross-cutting challenge is lack of human capacity that possess adequate skills to handle hydropower projects in the country. Furthermore, this study discussed practical solutions to address the identified problems facing hydro power in Uganda.</p> </abstract>

Present requirements of drawing up necessary changes in our petroleum usage to alleviate the detrimental aftermath of environmental contamination

Climate change is one of the major issues in the current world. Such climate change-related problems have not only problematic for the environment, but also a major issue for the world as a whole. Orderly and properly analysis made in such regards is the need of the time. And in no cases, there is any time left to ignore such necessary steps for mitigating the negative impacts of climate change on our environment. Climate change-related mitigation is all about reducing the overall release of greenhouse gas emissions that are ultimately heating up our world. Mitigation strategies consist of analyzing and taking necessary steps to make the utilization of natural resources more energy efficient. It includes helping cities in creating more feasible transportation systems, such as increasing the uses of electric vehicles and biofuels in place of crude oils; enhancing the utilization of renewable energy sources such as solar power plants, wind energy-related equipment, and small and large hydropower plants for generating the electricity. Mitigation measures include all such functioning that is undertaken to decrease and control the greenhouse emissions outflows. Adaptations of all such measures can support the reduction in the vulnerability factors which have adverse impacts on global climate and results in climate changes. When we considered the transportation sector of the country India, which heavily depends upon fossil fuel usages. And such led to challenges relating to air pollution, energy security, and greenhouse gas emissions, which directly related to the increase in the demand for taking some concrete and mitigation steps by making transportation and energy sectors much more effective and efficient. Petrol and diesel fuel accounts for more than 90% of India's transportation sector's energy utilization. The transportation sector is India's one of the fastest-growing as well as highly energy consuming sector with a growth rate of 6.8 %. Because of such huge demand in the transportation sector, the utilization of petroleum related product increased significantly. As a result of which 7 of the top 10 polluted cities in the whole world are belonging to country India. According to the world air quality report 2018. For instance, in Delhi, vehicle emissions have been considered as the major contributor to rising air pollution compared to all other sources including manufacturing sectors, households, thermal power plants, and the agricultural sector. In India, 2018 alone estimated death of 1.25 million people due to air pollution is about 12.5% of the total deaths. The Government of India has emphasized the target of making the country's energy sector more reliable, secure, and consistent & for achieving the above targets the government had decided to reduce the overall consumption of fossil fuel by 10% by the year 2022.

A Review on Real-Size Epoxy Cast Resin Insulators for Compact High Voltage Direct Current Gas Insulated Switchgears (GIS) and Gas Insulated Transmission Lines (GIL)—Current Achievements and Envisaged Research and Development

Due to the ever-increasing demand for electricity in the one hand and the environmental constraints to use clean energy on the other hand, the global production of energy from remote renewable sources, particularly from large hydropower plants and offshore wind farms and their connection to the grid are expected to grow significantly in the future. Consequently, the demand to carry this electric power by high voltage direct current (HVDC) technology will increase too. The most suitable HVDC power transmission technology to deliver large amounts of power, exceeding a capacity of 5 GW per bipolar system over long distances with lower losses is by using compact HVDC gas insulated transmission lines (DC GIL) and gas insulated switchgears (DC GIS) with rated voltage (maximum continuous operating voltage) of ±550 kV and 5000 A which are presently under development worldwide. Among the critical challenges for the development of these HVDC gas insulated systems, there are the epoxy cast resin insulators that are used to separate gas compartments also called spacers. Indeed, thorough research studies have been and still being carried out to well understand and clarify the electrical insulation characteristics of HVDC spacers using mainly cylindrical samples and small insulator models, where useful results have been obtained and proposed for implementation in real compact gas insulated systems. However, few practical investigations have been undertaken on real size spacers (product scale) to verify such research outcomes and validate the reliability of the spacers to collect experiences or for commercial use. This paper reviews the current achievements of real size HVDC spacers development. It describes the basic electric field calculation and spacers design, the verification of the insulation performance and validation testing. It gives today’s commercially available compact HVDC GIS/GIL and finally it presents the envisaged future research and development.

A New Admittance Approach Applicable to the Coordination Between the Loss-of-Excitation Protection and the Underexcitation Limiter

The performance of salient-pole synchronous generators protection is of great importance for the stability of power systems, as they are present in large hydropower plants, subject to various abnormal operating conditions such as three-phase or two-phase faults, electromechanical disturbances and loss-of-excitation. In this context, this work proposes a testing philosophy of salient-pole synchronous generators, in order to define more accurately the setting of the protections and controls of this asset. Thus, in the developed methodology, the admittance plan (G-B) proves applicable to analyze the coordination between the loss-of-excitation protection and the underexcitation limiter, as an alternative to the power (P-Q) and impedance (R-X) planes, normally employed in literature. In modeling the problem, real data for both the hydrogenerators and the electrical network are used. The simulations were performed in a hardware-in-the loop scheme integrated by a Real Time Digital Simulator and a physical relay. Thus, analyzes are made for situations of stable power swing and partial and total loss-of-excitation. The results are useful to prove, through the monitoring of relevant variables of the hydrogenerators, the feasibility and accuracy of the G-B plane in the coordination between the protection and the control of the synchronous machine.

Short-term generation scheduling of cascade hydropower plants with strong hydraulic coupling and head-dependent prohibited operating zones

A lot of large hydropower plants have been built in China in the past few decades. Large-capacity hydropower units usually have multiple prohibited operating zones (POZs) varying with the net head. Many cascade hydropower plants are hydraulically coupled because the distance between the upstream and downstream reservoirs is so small that the forebay water level of the downstream reservoir will influence the tailwater level of its immediate upstream reservoir. The integrated consideration of the strong hydraulic coupling between cascade hydropower plants, the head-dependent POZs of individual units, and other operation constraints make the daily operation of cascade hydropower plants very challenging for both operators and researchers. Therefore, this paper has developed an accurate optimization model for determining the hourly generation scheduling of cascade hydropower plants with strong hydraulic coupling and head-dependent POZs. The objective is to maximize the total profits of the cascade hydropower plants from selling electricity in the day-ahead market. To solve such a complicated mathematical model with non-convex and nonlinear features, the model is converted into a mixed-integer linear programming (MILP) formulation using multiple linear approximation techniques so as to take full advantage of the effective and mature commercial solvers. The MILP formulation focuses mainly on addressing two nonlinearities, namely the three-dimensional tailwater level curves and head-dependent POZs, which are approximated through the piecewise linear interpolations based on the meshing and triangulation technique. The developed model is applied to the optimal operation of the Tianshengqiao cascade hydropower plants which are located on the Hongshui River, China. The optimization results demonstrate that the proposed model is able to be applied in the short-term generation scheduling of cascade hydropower plants in different hydrological conditions, and the optimized total profits for the cascade hydropower plants on typical days in dry season and flood season are 1,809,842 USD and 1,856,964 USD, respectively. Moreover, the developed model is computationally efficient and produces more realistic and executable generation scheduling than the state-of-the-art optimization model which only considers the head-dependent characteristics of POZs without considering the strong hydraulic coupling.

Assessing concurrent effects of climate change on hydropower supply, electricity demand, and greenhouse gas emissions in the Upper Yangtze River Basin of China

Hydropower importantly provides flexible low-carbon electricity, however, climate change will affect the hydropower system through altering hydrologic regimes while also affecting electricity demands for heating and cooling that hydropower resources serve. This study assesses the effect of climate change on hydropower and electricity demand in the Upper Yangtze River Basin (UYRB) in China on the regional net electric load and greenhouse gas (GHG) emissions. This is accomplished by using climate projections from five global climate models (GCMs) to simultaneously force (1) a physically-based hydrological model and a statistically-based hydropower model to estimate the future generating capacity of 21 large hydropower plants in the UYRB and (2) an empirical electricity demand model accounting for socioeconomic and climatic factors. Under climate change, the projected hydropower generation in the UYRB tends to increase in the 21st century but is far less than the increase in electricity demand, increasing the gap between demand and supply. Future increases in overall electricity demand are driven by GDP growth, but climate change will alter the distribution of the seasonal electricity demand. Climate warming decreases electricity demand for heating in winter and increases electricity demand for cooling in summer, but ultimately increases demand. Meanwhile, there is an increasing mismatch between electricity demand and hydropower supply associated with inter- and intra-annual variations, owing to the temporal climate change and increase in compound climate extremes (droughts and heatwaves). Finally, meeting the gap between supply and demand due to climate change is estimated to contribute 79.0–184.6 and 50.6–316.2 MMT CO2e/yr of additional GHG emissions by the mid and end of 21st century, respectively.

Development of hydropower in Afghanistan for clean and sustainable energy

There are promising opportunities to produce clean and sustainable energy from micro, mini, small and large hydro power plants in Afghanistan. The Government of Afghanistan has planned to build several hydro power plants. One of them is Baghdara Dam Hydro Power project in Kapisa province and is expected to produce 210 MW. In the feasibility study, two dam axis configurations were considered, one creating a small reservoir, the other creating a large reservoir. However, a recommendation comparing advantages and disadvantages was not addressed. In this paper, we compare possible Baghdara Dam axis locations and recommend one for future construction that produces optimal electric power especially during the winter season and provides clean potable water to New Kabul City. We have determined that dam location A (with a small reservoir) would need a long tunnel to the power station which requires advanced technology and accurate geological surveying that is not available in Afghanistan. Axis D (with a large reservoir) will recharge downstream hydropower plants such as Kapar (120 MW), Naghlo (100 MW), Sarobi-1 (22 MW), Sarobi-2 (180 MW), and Daronta (12 MW). The large reservoir will also stop sediment ponding at the Naghlo hydropower reservoir. This case study shares an in-depth technical and practical lessons-learned with researchers, students, and practitioners.

Application of Geographical Information System in Environmental and Economic assessment of Run-of-river Hydropower in Central Vietnam

Conventional hydropower exploitation includes building large dams and reservoirs would pose significant impact to the environment. Recently there is trend to switch from building large hydropower plant to small and medium size, particular run-of-river hydropower plant. This study assesses the feasibility of installing run-of-hydropower scheme in the Vu Gia Thu Bon river basin with regards to the environmental and economic impact. The analysis was performed using GIS to identify the location of power plant that might have environmental constrains. The economic payback of each power plant was calculated and spotted on the digital maps. The methodology proposed in this study could be helpful for decision-makers in the preliminary identification of the most suitable locations to install run-of-river plants in the Vu Gia Thu Bon river basin.

The Punatsangchhu-I dam landslide illuminated by InSAR multitemporal analyses

We use multitemporal analyses based on Synthetic Aperture Radar differential interferometry (DInSAR) to study the slope adjacent to the large Punatsangchhu-I hydropower plant, a concrete gravity dam under construction in Bhutan since 2009. Several slope failures affected the site since 2013, probably as a consequence of toe undercutting of a previously unrecognised active landslide. Our results indicate that downslope displacement, likely related to the natural instability, was already visible in 2007 on various sectors of the entire valley flank. Moreover, the area with active displacements impinging on the dam site has continuously increased in size since 2007 and into 2018, even though stabilization measures have been implemented since 2013. Stabilisation measures currently only focus on a small portion of the slope, however, the unstable area is larger than previously evaluated. Highly damaged rock is present across many areas of the entire valley flank, indicating that the volumes involved may be orders of magnitude higher than the area on which stabilisation efforts have been concentrated after the 2013 failure. The results highlight that satellite-based DInSAR could be systematically used to support decision making processes in the different phases of a complex hydropower project, from the feasibility study, to the dam site selection and construction phase.

An Assessment of Hydropeaking Metrics of a Large-Sized Hydropower Plant Operating in a Lowland River, Lithuania

This paper discusses rapid flow and stage fluctuations in a large lowland river downstream from a large hydropower plant (HPP) in Lithuania. The main problem arises when the HPP is operating in peak mode. Such operation of HPP causes rapid flow and stage fluctuations, which can have a certain impact on river ecosystems. The study analyzes general abiotic indicators such as upramping and downramping rates and stage fluctuations downstream of the HPP. The main idea was to assess recorded stage upramping and downramping rates along the river downstream of large HPP. To assess stage fluctuation statistics, COSH software was used. A maximum upramping rate of 1.04 m/h and maximum downramping rate of 0.88 m/h were identified using data from temporary and permanent gauging stations. Obtained results revealed that stage fluctuations exceed ecologically acceptable rates up to 20 km downstream of HPP. The effect of hydropeaking fades out only at a chainage of 45 km downstream of HPP. In mountainous regions, ecologically acceptable rates are reached at much smaller distances. The study shows that the traditional coefficient of variation of stage fluctuation data can be used to describe hydropeaking indicators. The main results of this study can be used for environmental impact assessment downstream from HPPs.

Influences of small hydroelectric power plants on homogenization of the ichthyofauna in a tropical river

The native fishes of the Neotropical region have been heavily impacted by the construction of reservoirs that block the rivers in different degrees. Small Hydroelectric Power Plants (SHPP) have been an alternative way to take advantage of small electricity production potential, with low cost. However, there is no basis in the belief that SHPP have less deleterious effects on river habitat than large hydropower plants. The aim of this study was to evaluate eventual changes in the ichthyofauna because of the influences of SHPP in the middle reaches of a tropical river in south-eastern Brazil. The raised hypothesis is that SHPP change the ichthyofauna composition and increase the taxonomic and functional similarities (homogenization). Fish collections were carried out quarterly at six locations along a 20 km stretch of the Paraiba do Sul River, before and after the construction of the SHPP. The fish community structure changed between the two periods, with a decrease in the fish numerical abundance, whereas the species richness did not change. Sensitive species with specialized feeding habits (namely, Hartia loricariformis, Steindachineridium parahybae, Hypomasticus mormirops, Characidium alipioi, Chyphocharax gilbert, Corydoras nattereri and Pogonopoma parahybae) occurred only before the SHPP, being replaced by several species of Characiformes, among them four of genus Astyanax (namely, A. giton, A. hastatus, A. taeniatus, and A. intemedium) that are tolerant and omnivores; however, most of functional traits were maintained. The taxonomic dissimilarity increased significantly, whereas the functional dissimilarity did not differ between the two periods. The hypothesis of ichthyofauna homogenization was not confirmed in this study, probably because of the short time period since the SHPP construction.