Research projects on hydropower

Research reports on studies on the use of hydropower

Energy transition, climate change as well as water management and nature conservation requirements for waterways, combined with a growing need for energy, are global challenges that demand new and sustainable solutions. 

VERBUND promotes the understanding of the interactions and impacts of using hydropower on our environment through various research projects with the aim of contributing to sustainable, environmentally compatible solutions. The following studies give insight into current research activities, especially in the area of ecology and hydropower.

Sediment Management

The remediation of solids management in flowing bodies of water is a generational project. Higher level framework conditions (catchment area, sediment input, hydrology, etc.), local circumstances and different uses (flood protection, nature conservation, agriculture, power plant use, etc.), as well as legal framework conditions with sometimes different objectives (nature conservation, flood protection, WFD) represent big challenges for sediment management.

The complex of topics therefore requires a systematic consideration that takes into account river basin-related and local circumstances, issues of hydromorphological condition evaluation as well as underlying hydrological and sedimentological conditions.

Against this backdrop, VERBUND has been participating in research projects on this topic for many years – in some instances in a leadership capacity. For example, the University of Natural Resources and Life Sciences (Vienna) has spent several years systematically investigating the possibilities for improving sediment management along rivers in Austria influenced by power plants at the Christian Doppler Laboratory for Sediment Research and Management. Several investigations deal with the impacts and optimisation of reservoir flushing. Investigations in this regard took place within the scope of the Interreg project “ALPRESERV” on the Mur and in recent years on the Möll.


Baustelle Fischwanderhilfe Kraftwerk Altenwörth

Project descriptions of sediment management

Achieving sustainable operation of hydropower plants requires a sound understanding of the dynamic processes in flowing bodies of water. One management challenge and an important point for the river as an ecosystem is the transport of sediments.

The CD Laboratory researches the principles of erosion and sedimentation and analyses the transport and remobilisation of solids. Through optimised sediment management, ecological, economic and technical solutions can be elaborated, flood protection ensured and acceptance in society increased.

A better understanding of the process is acquired in a combination of laboratory trials and investigations in the field. The dimensions considered extend from the μm range to entire river catchment areas.

The findings obtained serve as a basis for the development of new monitoring and modelling technologies and for the creation of new standards for the use of hydropower. They additionally support the development of sustainable management concepts in riverscapes.

Martin Mühlbauer, Wolfgang Lauber, Florian Derntl, Clemens Ratschan, Roland Schmalfuß, Gerald Zauner (2022) Dynamische Dotation und Sedimentmanagement zur Gewährleistung funktioneller Fließgewässerhabitate in Fischwanderhilfen. Österreichische Wasser- und Abfallwirtschaft (2022):

Cornelia Haeck, Ralf Klocke, Karl-Heinz Strasser, Georg Loy, Walter Reckendorfer (2022) Workshop zum Sedimentmanagement an Stauanlagen an großen Gewässern im Donaueinzugsgebiet. WASSERWIRTSCHAFT, Band 112, Ausgabe 6, Seiten 54-57

Walter Reckendorfer (2022) Sedimentmanagement in Stauketten-Ökologische Ziele und Herausforderungen. WASSERWIRTSCHAFT, Band 112, Ausgabe 2-3, Seiten 57-60

Georg Loy  (2022) Sedimentmanagement in Staustufenketten - Notwendigkeit, Herausforderungen und Umsetzungsbeispiele. WASSERWIRTSCHAFT, Band 112, Ausgabe 2-3, Seiten 45-50

Roland Schmalfuß (2022) Sedimentmanagement bei Stauanlagen: Herausforderungen und Lösungen. WASSERWIRTSCHAFT, Band 112, Ausgabe 2-3, Seiten 65-68

Reckendorfer, W., Badura, H., & Schütz, C. (2019). Drawdown flushing in a chain of reservoirs—Effects on grayling populations and implications for sediment management. Ecology and Evolution, 9(3), 1437-1451.

Badura, H., Knoblauch, H., Schneider, J., Harreiter, H., & Demel, S. (2007). Wasserwirtschaftliche Optimierung der Stauraumspülungen an der oberen Mur. Österreichische Wasser- und Abfallwirtschaft, 5(59), 61-68.

Hauer, C., Haimann, M., Holzapfel, P., Flödl, P., Wagner, B., Hubmann, M., ... & Schletterer, M. (2020). Controlled Reservoir Drawdown—Challenges for Sediment Management and Integrative Monitoring: An Austrian Case Study—Part A: Reach Scale. Water, 12(4), 1058.

Hauer, C., Holzapfel, P., Flödl, P., Wagner, B., Graf, W., Leitner, P., ... & Schletterer, M. (2020). Controlled reservoir drawdown—Challenges for sediment management and integrative monitoring: An Austrian case study—Part B: Local Scale. Water, 12(4), 1055.

Surge & Drop

Due to the energy transition and the increased use of volatile renewable energy required for it, it is becoming increasing important to provide stabilising and flexible balancing measures for the grid. (Pumped) storage power plants and their ability to store energy and make it available as and when needed are of fundamental importance here.

However, the sections of water in the surge diversion sections can be ecologically impeded by short-term draining fluctuations (surge & drop).  An in-depth evaluation of different operating methods of hydropower plants is currently possible only to a limited extent, due to a lack of sufficient expertise.

The goal is to achieve optimal improvements for the water ecology without this resulting in considerable economic and business management restrictions in power plant operation. This would negatively impact implementation of the steps needed to achieve fully renewable energy generation.

Together with the University of Natural Resources and Life Sciences, the Federal Ministry of Agriculture, Regions and Tourism (BML) as well as numerous partners, VERBUND has initiated several research projects (SuREmMa, SuREmMa+, ÖkoResch).

The projects deal with fundamental questions such as the influence of surge and drop on the drift and stranding rates of aquatic lifeforms and subsequently on the systemic and economic impacts of possible compensation measures.

Ultimately, the projects should contribute to determining “good ecological potential” in the sense of the Water Framework Directive for the stretches of water affected by surge. Initial results are evaluation criteria and recommend actions for the best possible surge damping. In the ÖkoResch project, launched in 2021, the elaborated approaches are tested for their applicability and impact and extensively accompanied by scientific support.

Project descriptions on Surge & Drop

The research project investigates the impacts of surge and residual water loads on aquatic life. The possibility of alleviating these loads through ecological measures was investigated and evaluated along selected pilot sections. 

At the same time, the energy industry and system-relevant restrictions that can arise during the implementation of ecological measures are assessed. The project also elaborates scientific principles on the possibilities and impacts of an improved residual water discharge, especially in the high mountains. The research work will continue for a period of six years. The long project duration is mainly due to the necessary field work in the high alpine habitat. This is carried out in influenced waters and reference waters. In addition, dotation trials at representative trial sites will be started. Building on this, an ecological evaluation and monitoring system will be developed by the end of the project term.

The basis for the current research project ÖkoResch was the project “Sustainable River Management – Energy and environmental evaluation of possible surge-damping measures”, with the two modules “SuREmMa” and “SuREmMa+”. For the first time, these projects created the basis for an Austria-wide, standardised evaluation tool for surge remediation measures. 

In a first step, an economic and ecological evaluation system for surge-damping measures, such as operation restrictions, surge damping ponds, surge discharge power plants and morphological remediation measures, was developed. From an economic perspective, restrictions on the use of storage power plants result directly in balancing energy having to be provided for grid stabilisation through fossil energy sources or nuclear energy in the event of the absence of volatile forms of energy such as wind and solar. The water ecological effectiveness of the measures was compared with these economic and operating effects and evaluated. The evaluation toolset was representatively tested at ten Austrian storage power plants. 

In SuREmMa+, the measures evaluation was refined, a monitoring concept matched to the evaluation methods was developed and applied to selected case studies. The evaluation encompasses the stranding and drifting of aquatic organisms (fish, macrozoobenthos), the availability and quality of habitat as well as an estimate of the economic impacts.

Using the elaborated evaluation criteria, it is possible to put in place targeted measures for certain sections of waterway in order to achieve a good aquatic-ecological condition or potential under consideration of ecological and energy industry impacts.

Schmutz S., Fohler N., Friedrich T., Fuhrmann M., Graf W., Greimel F., Höller N., Jungwirth M., Leitner P., Moog O., Melcher A., Müllner K., Ochsenhofer G., Salcher G., Steidl C., Unfer G., Zeiringer B. 2013: Schwallproblematik an Österreichs Fließgewässern – Ökologische Folgen und Sanierungsmöglichkeiten. BMFLUW, Wien.

Greimel, F., Neubarth J., Fuhrmann, M., Führer, S., Habersack H., Haslauer, M., Hauer, C., Holzapfel, P., Auer, S., Pfleger, M., Schmutz, S. & Zeiringer, B. (2017): SuREmMa, Sustainable River Management - Energiewirtschaftliche und umweltrelevante Bewertung möglicher schwalldämpfender Maßnahmen. Forschungsbericht, Wien, 92 Seiten.

Greimel, F., Neubarth, J., Fuhrmann, M., Zoltan, L., Zeiringer, B., Schülting, L., Führer, S., Auer, S., Leitner, P., Dossi, F., Holzapfel, P., Pfleger, M., Leobner, I., Sumper, R., Pazmandy, J., Graf, W., Hauer, C. und Schmutz, S.: SuREmMa+: Entwicklung einer Methode zur ökologischen und energiewirtschaftlichen Bewertung von Maßnahmen zur Minderung von negativen schwall- und sunkbedingten ökologischen Auswirkungen. Forschungsbericht, Wien 2021, 158 Seiten.

Greimel, F., Grün, B., Hayes, D. S., Höller, N., Haider, J., Zeiringer, B., ... & Schmutz, S. (2022). PeakTrace: Routing of hydropeaking waves using multiple hydrographs—A novel approach. River Research and Applications. 

Consistency & Habitat

A central demand of the EU’s Water Framework Directive (WFD) and the national water management plans that build upon it involves restoring the passability of structures that lie across flowing waterways. This also requires appropriate measures to be put in place at the run-of-river power plants of VERBUND. 

Experiences in fish habitats to date show that the restoration of technical consistency in itself is not enough to achieve the required objectives of good ecological condition or good ecological potential. To achieve these objectives, a systematic approach is required that places the creation of habitat above the goal of pure consistency. Key habitats for our domestic river fish are undeveloped, flat gravel banks, but above all dynamic side waters that are used as spawning and juvenile fish habitats on the one hand, and as migration corridors on the other.

Against this backdrop, several research projects are currently in progress that deal with different aspects of fish consistency, habitat availability and the habitat selection of fish. Open questions concern aspects of the findability and passability of fish passes on the one hand, and the cumulative or large-scale impact of measures on the other.

A research team headed up by Univ. Prof. Helmut Mader at the University of Natural Resources and Life Sciences, Vienna, mainly focuses on the question: "What are the key stimuli that trigger fish migrations?" To answer this, state-of-the-art methods are applied and further developed which enable an analysis of the flow, light and temperature conditions, but also of the acoustic environment around the entrances to fish passes. 

The large-scale impact of habitat improvements in combination with the interconnection of waterway systems remains under-researched. To obtain a better understanding of this, research projects were started both on the Austrian Danube under the direction of Univ. Prof. Thomas Hein from the University of Natural Resources and Life Sciences, Vienna, and on the Bavarian Inn under the direction of Univ. Prof. Jürgen Geist at the Technological University of Munich, which deal with the various focal points of this question.

Project description of Consistency & Habitat

For many years now, projects to improve habitat and species diversity in aquatic habitats have been carried out on the Danube. However, little is known about the cumulative added value of the individual projects and their spillover effects. The CD Laboratory MERI, under the professional direction of the University of Natural Resources and Life Sciences, deals with these questions.

To better understand the dynamic processes occurring in the Danube, the meta-ecosystem approach combines biological processes, human activities and ecosystem services on different spatial and temporal scales. Thus, for example, migration behaviour and the habitat selection of fish are investigated to identify habitat preferences and deficits. Food web relationships in different sections of river are also analysed, as are the ecosystem performance of the river landscape and the way in which fishing impacts the river. The findings obtained should in future be used to develop strategies for even more purposeful ecological measures and facilitate the taking of targeted management decisions.

Initial results show that the newly created habitats on the Traisen or Grosse Tulln are accepted by Danube fish to a large extent as spawning habitats. The large bypass rivers created on the Danube within the scope of LIFE (LIFE-NETZWERK-DONAU.AT) even enable fish from the Freudenau reservoir to spawn in the newly created underflow of the Traisen (LIFE-TRAISEN.AT).

Passive Integrated Transponder (PIT) tag technology is in used on a large scale in several research projects in Austria and Bavaria. It is particularly good at recording the migration behaviour of fish over a longer period of time and reconstructing their movement patterns.

It enables the investigation of passability, findability and use of fish passes as a means of descent, as well as the temporal and spatial progression of the migrations, the distribution of the fish and the use of habitat. The objective of the investigations is to improve understanding of the habitat requirements of fish fauna and in particular to investigate pan-regional questions of migration behaviour and habitat selection. In this way, it should be possible to better assess the effectiveness of aquatic ecological measures in the future. These findings can subsequently be used for the further development of previously implemented land restoration measures and fish passes.

PIT tags are passive transponders used for the electronic marking of fish. When marked fish swim past an antenna installed in the river or in a fish pass, they are registered and identified. With the aid of recordings made in a waterway system with many antennae, the migration behaviour of both individual fish and entire populations can be traced. The project area being worked on by VERBUND extends from the power plant at Freudenau near Vienna along the Danube as far as the Inn in Bavaria. 

Initial investigations are revealing some surprising results. For example, it was discovered that shipping locks are used by fish to a not inconsiderable extent for migration purposes. They also showed that the fish - in contrast to prevailing opinion - also use the fish passes to migrate downstream. It was also confirmed that several species exhibit a distinct sense of homing, i.e. they return to the same stretch of water every year to spawn.

Measures to protect the fish populations in waterways characterised by hydropower have so far concentrated almost entirely on longitudinal consistency for fish. These measures are mainly aimed at fish that migrate over medium and long distances. Fish that migrate of short distances in particular can probably benefit much more from habitat-improving measures in waterways and their wetlands than from the pure restoration of consistency.

In order to better understand the importance of individual measures and their interconnectedness for the fish populations in the Inn, a research concept was initially elaborated within the scope of preliminary investigations in 2013-2015. 

Building on those, practical field studies have been carried out by the Technical University of Munich since 2015. The main project is set up for a period of ten years and arranged into three project sections investigating measures in the side and still waters of the Innaue wetlands (Part I), bank widening and hydrological structures in the Inn main channel (Part II) and the interconnecting of the various partial habitats (Part III). Results obtained so far clearly show that the near-natural bypass rivers represent an important habitat for fish and benthic invertebrates and function as a source of biodiversity for the main channel.

Since 2018, the research project has dealt with a range of open questions on what triggers fish migrations and how fish orientate themselves in waterways. Current opinion assumes that fish primarily orientate themselves in response to hydraulic stimuli. Other external factors such as light, acoustic stimuli, oxygen content or temperature are largely ignored. Field investigations creating a link between the ascent behaviour of migrating fish and the various key stimuli in a high temporal resolution have so far been lacking.

The four stimuli of acoustics, light, water temperature and flow are investigated within the scope of the project. Thermal stimuli, acoustic stimuli and light stimuli are generated in situ at the entrance to the fish pass. To measure the flow and temperature conditions, drone-supported, high-resolution optical cameras and thermal imaging cameras are used. The flow is measured contactlessly using optical methods such as Particle Image Velocimetry (PIV) and Particle Tracking Velocimetry (PTV). This involves photographing particles in the water at short time intervals. The direction and velocity of movement can be determined from the positions of the particles. Moreover, existing software tools are trialled, further developed and then adapted and optimised to the questions at hand. 

Results obtained to date indicate that of the parameters investigated, only the temperature plays a role in triggering fish migration and the way in which fish orientate themselves. No effect of acoustic stimuli, flow and light could be established. These results also call into question the currently prevailing paradigm that river fish need a distinct “lure current” in order to find the entrance to fish passes.

Bondar-Kunze, E., Funk, A., Haidvogl, G., Unfer, G., Muhar, S., Hohensinner, S., ... & Hein, T. (2022). Der Meta-Ökosystem Ansatz in der Praxis–Integration von hydromorphologischen Veränderungen und menschlichen Eingriffen in die Meta-Ökosystem-Theorie zur Entwicklung eines nachhaltigen Flussmanagements an der österreichischen Donau. Österreichische Wasser-und Abfallwirtschaft, 1-9.

Reckendorfer, W., Michael Schabuss and Regina Petz-Glechner. “Abwärtswanderung durch eine Fischaufstiegsanlage - neue Erkenntnisse durch Untersuchungen mittels PIT-Tags.” WASSERWIRTSCHAFT 113 (2023): 31 - 34.

Reckendorfer, W., Zornig H., Schabuss, M., & Petz-Glechner, R. (2023). Effekte der Dotation auf die Auffindbarkeit von Fischwanderhilfen – Ergebnisse von PIT Tag Untersuchungen an der Donau. Wasserbausymposium Wallgau

Loy, G., & Reckendorfer, W. (2022). Creation and Use of “Compensation” Habitats—An Integrated Approach. In Novel Developments for Sustainable Hydropower (pp. 157-165). Cham: Springer International Publishing.

Nagel, C., Mizerakis, V., Pander, J., & Geist, J. (2022). The overlooked contribution of a fish bypass channel to the density and diversity of macroinvertebrate drift in a heavily modified river system. River Research and Applications, 38(10), 1696-1707.

Pander, J., Nagel, C., Ingermann, H., & Geist, J. (2022). Water level induced changes of habitat quality determine fish community composition in restored and modified riverbanks of a large alpine river. International Review of Hydrobiology, 107(1-2), 46-59.

Nagel, C., Mueller, M., Pander, J., Stoeckle, B. C., Kuehn, R., & Geist, J. (2021). Going with the flow: Spatio‐temporal drift patterns of larval fish in a large alpine river. Freshwater Biology, 66(9), 1765-1781.

Nagel, C., Mueller, M., Pander, J., & Geist, J. (2020). Making up the bed: Gravel cleaning as a contribution to nase (Chondrostoma nasus L.) spawning and recruitment success. Aquatic Conservation: Marine and Freshwater Ecosystems, 30(12), 2269-2283.

Nagel, C., Pander, J., Mueller, M., & Geist, J. (2020). Substrate composition determines emergence success and development of European nase larvae (Chondrostoma nasus L.). Ecology of Freshwater Fish, 29(1), 121-131.

Brandl, A., Käfer, S., Fillitz, B., Pinter, G., Laaha, G., & Mader, H. (2020). Relevance of key stimuli, in particular light and acoustics, for the findability of fish passes. Österreichische Wasser-und Abfallwirtschaft, 72, 187-201.

Brandl, A., Käfer, S., Laaha, G., & Mader, H. (2022). Temperatur Als Schlüsselreiz Für Die Auffindbarkeit von Fischaufstiegsanlagen. Wasserwirtschaft, 12-18.

Brandl, A., Laaha, G., Käfer, S., & Mader, H. (2022). Key Factors for the Findability of Fish Passes in Large Epipotamal Rivers: The Case of the River Drava. Water, 14(10), 1530.

Perks, M. T., Dal Sasso, S. F., Hauet, A., Jamieson, E., Le Coz, J., Pearce, S., ... & Manfreda, S. (2020). Towards harmonisation of image velocimetry techniques for river surface velocity observations. Earth System Science Data, 12(3), 1545-1559.

Strelnikova, D., Paulus, G., Käfer, S., Anders, K. H., Mayr, P., Mader, H., ... & Schneeberger, R. (2020). Drone-based optical measurements of heterogeneous surface velocity fields around fish passages at hydropower dams. Remote Sensing, 12(3), 384.

Strelnikova, D., Perks, M. T., Paulus, G., Käfer, S., Anders, K. H., Mayr, P., ... & Schneeberger, R. (2022). Rapid Detection of the Change in Surface Flow Patterns Near Fish Passages at Hydropower Dams With the Use of UAS Based Videos Under Controlled Discharge Conditions. Frontiers in Remote Sensing, 3, 14.

Strelnikova, Dariia, Gernot Paulus, Sabine Käfer, Karl Anders, Peter Mayr, Helmut Mader, Ulf Scherling and Rudi Schneeberger. “Drohnenbasierte optische Ermittlung von heterogenen Oberflächenströmungsmustern in der Nähe von Fischaufstiegshilfen” AGIT Journal Angew. Geoinformatik 6 (2020): 206-216.

Käfer (S. 2019) Verbesserung der ökonomischen Effzienz bei gleichbleibender ökologischer Effektivität. WASSERWIRTSCHAFT, Band 109, Ausgabe 10, Seiten 45-47

Thomas Kaufmann, Gerd Frik, Roland Schmalfuß, Gertrud Haidvogl, Jürgen Eberstaller, Helmut Wimmer, Mathias Jungwirth (2018) LIFE+ Traisen: Der lange Weg zum neuen Fluss. Österreichische Wasser-und Abfallwirtschaft, Band  70, Ausgabe 5-6, Seiten 264-271

Oberlerchner D. (2018) LIFE Netzwerk Donau Umsetzung ökologischer Projekte im Spannungsfeld von Kosten und Schutzwasserwirtschaft. Wasserbausymposium 2018 Wasserwirtschaft Innovation aus Tradition, Seiten 147-152 

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