Robert Michael Boes

• Director at ETH Zurich

Electrified fish guidance and trash racks at water intakes are a promising technology to divert downstream moving fish away from turbines and towards a safe bypass route. Current recommendations on pulsed direct current (pDC) waveforms to electrify such racks are based on a limited number of field studies, and hence investigations comparing pDC wav...

Water storage and water reservoirs are key to the Water-Energy-Food-Ecosystem (WEFE) nexus, especially when they store water for hydropower. However, there is not a uniform view on existing energy storage capacity and on the potential for future deployment of pumped-storage hydropower (PSH) and conventional reservoir storage hydropower (RSHP) acros...

Sedimentation challenges water reservoir operations globally, particularly for storage hydropower plants (HPPs), necessitating effective management strategies. One such strategy, fine sediment venting through turbines, though effective in managing sediment continuity, increases hydro-abrasive erosion on turbines due to the additional sediment load....

Desanding facilities (DFs) limit particle sizes and reduce the suspended sediment load in hydropower plants. Multiple successive tranquilizing racks (TRs) at settling chamber inlets are a cost-efficient structural measure to homogenize the flow and reduce local velocities and turbulence in the chambers. We summarized the state of the art of TRs and...

The analysis of bubbly two-phase flows is challenging due to their turbulent nature and the need for intrusive phase-detection probes. However, accurately characterizing these flows is crucial for safely designing critical infrastructure such as dams and their appurtenant structures. The combination of dual-tip intrusive phase-detection probes with...

Most fish species are ectothermic and rely on behavioral strategies to control their body temperature in heterothermal environments. Both thermotaxis and thermokinesis have been suggested as important underlying mechanisms. However, to what extent these behaviors allow fish to respond to rapid (timescales of minutes) and strong thermal disturbances...

Most fish species are ectothermic and rely on behavioral strategies to control their body temperature in heterothermal environments. Both thermotaxis and thermokinesis have been suggested as important underlying mechanisms. However, to what extent these behaviors allow fish to respond to rapid (timescales of minutes) and strong thermal disturbances...

Wave assessment is essential for the design and monitoring of coastal structures, assisting engineers to ensure infrastructure integrity. Common methods for wave monitoring involve measuring water surface height or hydrostatic pressure, with pressure-based systems offering significant advantages, especially in the detection of small wave heights su...

The Proceedings of the 10th IAHR International Symposium on Hydraulic Structures (ISHS 2024), held at ETH Zurich, Switzerland, from June 17 to 19, 2024, followed by the 9th International Junior Researcher and Engineer Workshop (9th IJREWHS) on Hydraulic Structures on June 20, contain technical papers on diverse and novel aspects of hydraulic struct...

The present study deals with the development, construction, operation, and success-control of the downstream fish passage system for the pilot hydropower plant (HPP) Herrentöbeli on the Thur River in Switzerland. This system is called foiledshape Curved-Bar Rack – Bypass System (f-CBR-BS) and functions as mechanical behavioural fish guidance system...

Hydropower plants (HPPs) and other barriers interrupt the longitudinal connectivity in river networks, which hinders or delays fish migration. One potential solution for downstream fish passage is to use conventional spillways and weirs, e.g., in periods of pronounced fish downstream migration. However, the knowledge of fish injury and mortality du...

Wood plays an important ecological role in rivers. Yet challenges arise when large wood (LW) is mobilised and transported during floods. Due to a lack of quantitative data, movement behaviour of LW during floods is still not well understood to date. A proof-of-concept study was conducted at three Swiss rivers to test state-of-the-art sensor-tagged...

Most fish species are ectothermic and rely on behavioral strategies to control their body temperature in heterothermal environments. Both thermotaxis and thermokinesis have been suggested as important underlying mechanisms. However, to what extent these behaviors allow fish to respond to rapid (timescales of minutes) and strong thermal disturbances...

Sediment Bypass Tunnels (SBTs) are proven to be an effective measure to reduce or even stop reservoir sedimentation by bypassing sediment laden flows around reservoir dams to the downstream river reach. They are mostly used in Switzerland, Japan, and Taiwan. However, hydraulic and sedimentological operating conditions and the resistance of the inve...

Modeling the morphological response of gravel-bed rivers subject to repeated sediment bypass tunnel operations. Introduction: Sediment bypass tunnels (SBTs) are operated during floods to re-establish sediment continuity past dams with the ultimate goal of decreasing accumulation in reservoirs. Depending on the location of the intake structure and o...

As climate warms, hydrology and geomorphology in glacierized catchments are evolving, changing sediment export from these catchments, thus impacting downstream ecosystems and communities. Currently, much uncertainty persists regarding interactions among geomorphic processes that evacuate sediment from glacierized catchments. Here, we present a catc...

To study the fish behavioral response to up- and downstream fish passage structures, live-fish tests are conducted in large flumes in various laboratories around the world. The use of multiple fisheye cameras to cover the full width and length of a flume, low color contrast between fish and flume bottom and non-uniform illumination leading to fish...

Fish guidance racks with adjacent bypass systems (FGR-BSs) are effective solutions for safe downstream passage at hydropower plants for many fish species. However, the bypass discharge is usually lost for electricity production because it reduces the available turbine discharge. Therefore, a gate with local openings is often installed at the bypass...

Spillways are critical appurtenant structures of reservoir dams, designed to prevent uncontrolled overtopping during extreme flood events. The highly turbulent nature of free-surface flows on spillways typically results in entrainment of air, forming a chaotic air-water mixture flow. The accurate description of such flows for a range of chute slope...

Dear colleagues, We are pleased to announce that the 10th International Symposium on Hydraulic Structures (ISHS) will take place at ETH Zurich, Switzerland on the 17 – 19 June 2024. We invite you to submit an abstract for a presentation at the 10th ISHS. Abstract should be 1-page maximum and should follow the guidelines on https://ishs2024.ethz.c...

Infolge gesetzlicher Grundlagen (EU-Wasserrahmenrichtlinie, Schweizer Gewässerschutzgesetz) haben der Fischschutz und Fischabstieg an Wasserkraftanlagen (WKA) in den letzten Jahren in Mitteleuropa stark an Bedeutung gewonnen. In der Schweiz müssen bis 2030 an rund 700 WKA Fischabstiegsanlagen saniert oder neu errichtet werden (Baumgartner et al., 2...

Schwemmgut kann an Hochwasserentlastungsanlagen von Talsperren Verklausungen verursachen, welche die Abflusskapazität maßgeblich reduzieren. Wird das erforderliche Freibord infolge des resultierenden Aufstaus nicht mehr eingehalten, kann es gar zur Überströmung von Sperrenbauwerken kommen. Ausreichend weit ins Oberwasser auskragende Pfeiler vermöge...

Das Kraftwerk (KW) Saldur ist eine alpine Kleinwasserkraftanlage im Norden Italiens mit teilweise vergletschertem Einzugsgebiet. In den ersten Betriebsjahren wurde deren Pelton-Turbine stark abgenutzt. Um den hydro-abrasiven Verschleiß zu reduzieren, wurden das Laufrad und die Düsen durch beschichtete Bauteile ersetzt. In einem Forschungsprojekt wu...

Reservoir dams play a significant role in society and the economy. Low-level outlets (LLOs) are key safety devices providing reservoir drawdown for maintenance and emergency purposes, sediment flushing, and release of environmental flow. High velocities and turbulence levels of the free-surface flow lead to air entrainment and air transport along t...

Hydro-abrasive erosion negatively affects the energy and cost efficiency of hydropower plants (HPPs). To optimize their operation, temporary shutdowns during exceptionally high suspended sediment loads are an option. In a case study at HPP Fieschertal with large, hard-coated Pelton turbines, a threshold value of suspended sediment concentration (SS...

Quantification and assessment of large wood (LW) accumulations in fluvial systems is still considered difficult due to the complex nature of wooden deposits. Although knowledge about volumetric measures and porosity parameters of LW accumulations is crucial for the prediction of hydraulic and geomorphic effects, it has not yet been possible to obta...

During flood events, river topography and fluvial habitats can change drastically, potentially affecting the ecological status. In case of multiple floods, whether each single event modifies the habitat characteristics in the same direction or not, is still an open question. We gathered high quality topographical data of one braided Alpine reach be...

Reach‐scale widening of channelized rivers can locally reactivate morphodynamic processes and increase habitat heterogeneity. Following process‐based restoration principles, construction efforts are often limited to bank protection removal and local bank erosion initiation. Despite significant advances in our understanding of fluvial processes, the...

The present study deals with the hydraulic and fish-biological performance of an innovative curved-bar rack bypass system (CBR-BS). CBR is a mechanical behavioral fish guidance structure typically combined with a BS, that was developed at VAW of ETH Zurich for safe downstream fish passage at hydropower plants. A hydraulically optimized CBR with a f...

Downstream moving fish may have to pass through turbines or spillways of run-of-river hydropower plants (HPPs), which can result in life-threatening injuries. Fish guidance structures such as a vertical curved-bar rack (CBR) or horizontal bar rack (HBR) in combination with a bypass can safely guide different fish species around HPPs, thereby provid...

Mechanical behavioural fish guidance racks (FGR) with vertical bars are a promising technical solution for the safe downstream movement of fish at run-of-river hydropower plants (HPP) and water intakes. They do not pose a physical barrier to most fish but rather create flow patterns that deter fish from passing the bar rack and guide them towards a...

Chapter 7 deals with the fish guidance structures (FGS) with narrow bar spacing and focuses on both vertically inclined and horizontal bar racks as well as vertically inclined perforated plate with bypass systems. These FGSs are physical barriers and placed in front of a water intake with either vertical or horizontal angle to the flow direction. T...

This chapter deals with the fish guidance structures (FGS) with wide bar spacing and focuses on Curved-Bar Rack-Bypass Systems (CBR-BS) (Beck 2020) for fish protection and fish guidance at water intakes. In: Boes RM (ed) VAW-Mitteilung, vol 257. VAW, ETH Zurich, Switzerland. https://vaw.ethz.ch/en/the-institute/publications/vaw-communications/2010-...

Air-water flows commonly occur in hydraulic structures such as spillway chutes and low-level outlets. In high-velocity flows, air entrainment is a dominant feature and must be considered for a sound design of these safety-relevant appurtenant structures. Most applied research and engineering design recommendations for such structures have been base...

High-velocity air-water flows are frequently observed at hydraulic structures, e.g., spillways and low-level outlets, and they are characterized by a strong interaction between the two phases and by void fractions ranging from a few percent to up to 100% at the free surface. Intrusive phase-detection probes represent the most widely used instrument...

Sedimentation is one of the main eco-morphological and technological challenges associated with reservoirs. Sedimentation not only reduces the functional capacity of a reservoir by filling it, but also changes downstream sediment dynamics and habitat availability for the aquatic biota. Additionally, dams hinder free bi-directional fish passage, eme...

Hydropower plants act as a barrier to fish moving in rivers. Fish guidance structures like angled bar racks with horizontal or vertical bars are used to protect downstream moving fish from turbine passage, guiding them to a bypass as an alternative passage corridor. The function of the bypass system is to safely collect, carry and reintroduce the f...

Turbinen von Hoch- und Mitteldruck-Wasserkraftanlagen können bekanntlich durch Schwebstoffpartikel im Wasser stark abgenutzt werden, was zu erheblichen Unterhaltskosten, Wirkungsgradabnahmen, Minderproduktion und somit zu Ertragseinbussen führt. Diese Problematik wurde am Hochdruck-Laufwasserkraftwerk Fieschertal (Wallis) in einem Forschungsprojekt...

Sediment management at reservoirs is gaining importance to maintain the active storage volume to fulfil the reservoir’s purpose(s) and the exigencies as to the eco-morphological sediment requirements of river reaches downstream of reservoir dams. For reservoirs where delta formation by bed load deposition is the governing sedimentation process, the...

Due to climate change and political efforts to increase the share of renewable energy sources, more large-scale water and electricity storage up to the seasonal timescale is needed besides a higher annual hydropower production. A possible response to these demands is to implement new multipurpose reservoirs in regions of retreating glaciers. Anothe...

This paper investigates the hydraulics and fish guidance efficiency of a Horizontal Bar Rack-Bypass System (HBR-BS) installed at a hydropower plant with a design discharge of 33 m³/s. The HBR is placed at a horizontal rack angle of 38° to the flow direction with clear bar spacing of 20 mm. The BS has a vertical-axis flap gate with two openings. The...

During their life cycle, fish carry out distinct movements within rivers and migrate upstream and downstream to reproduce, to feed, and to shelter in refuge habitats. During downstream movements, they can incur severe injuries that may be lethal directly or indirectly over time when passing through hydropower plants or when being entrained at other...

Turbine wear caused by hydro-abrasion due to suspended sediment in the turbine water has a negative impact on the power production and revenue of hydropower schemes. Efficiency of desanding facilities that reduce suspended sediment load ahead of turbines is key to limiting hydro-abrasion. Existing facilities built according to common design approac...

Numerical hydrodynamic models enable the simulation of hydraulic conditions under various scenarios and are thus suitable tools for hydropeaking related assessments. However, the choice of the necessary model complexity and the consequences of modelling choices are not trivial and only few guidelines exist. In this study we systematically evaluate...

The ambition of this symposium was to review and create knowledge and praxis in bedload management, support the implementation of restoration measures in Switzerland and strengthen the international network among scientists and practitioners. Switzerland has the legal goal and the financial tools to restore its rivers from the impacts of sediment...

Horizontal bar rack bypass systems (HBR-BS) are characterized by a horizontal bar rack (HBR) with narrow clear bar spacing of 10–20 mm and an adjacent bypass (BS) to efficiently protect and guide downstream moving fish at water intakes. The small bar spacing may lead to operational challenges, such as clogging and high head losses. This study inves...

Although horizontal bar rack bypass systems (HBR-BS) are a state-of-the-art technology for fish downstream passage, which has been installed at many European hydropower plants in recent years, in-depth technical knowledge regarding hydraulics, operational aspects, and fish behaviour has so far been missing. To fill these research gaps, we conducted...

A new type of fish guidance structure with vertical, curved bars in combination with a bypass system (BS) represents a promising technical solution for fish protection and fish guidance at run-of-river hydropower plants and water intakes. These so-called curved-bar rack bypass systems (CBR-BS) are characterized by low hydraulic head losses, a symme...

Horizontal bar rack bypass systems (HBR-BS) are a state-of-the-art technology for fish downstream passage, which has been installed at many European hydropower plants in recent years. However, in-depth technical knowledge regarding hydraulics, operational aspects, and fish behavior has so far been missing. This research gap was filled with an exten...

About 50% of all hydropower plants (HPPs) worldwide were originally commissioned more than 40 years ago, so that the advanced age of the fleet is a major concern across all continents, and especially in Europe. The modernization of HPPs can generate several benefits in terms of generation, flexibility, safety, operation, and may have neutral or eve...

Anthropogenic alterations of sediment supply and transport processes may impact the ecological state of riverscapes and threaten infrastructure along the river. Sediment replenishment is one restoration method that is employed in channels impacted by sediment deficit. We performed flume experiments to investigate the channel bed response of a chann...

Hydro-abrasive erosion on hydraulic turbines is economically and energetically important. To better understand the causes and consequences of turbine erosion and to further develop mitigation measures, the suspended sediment concentration (SSC) and size distribution of mineral particles in the turbine water of the 64 MW high-head run-of-river hydro...

Acoustic Doppler Current Profilers (ADCPs) are widely used for flow measurements in field. A moving-vessel ADCP application decreases the measurement duration compared to stationary measurements. The minimum number of required transects at each cross section for accurate velocity and discharge measurements under different flow conditions is a funda...

Hydro-abrasive erosion on hydraulic turbines is economically and energetically important. To better understand the causes and consequences of turbine erosion and to further develop mitigation measures, the suspended sediment concentration (SSC) and size distribution of mineral particles in the turbine water of the 64 MW high-head run-of-river hydro...

There are many options to reduce reservoir sedimentation. For hydropower reservoirs, one option is to increase the transport of fine sediments through power waterways and hence the turbines. This has ecological advantages because the suspended sediment concentrations (SSC) in downstream river reaches are similar to pre-dam conditions. However, the...

Habitats that mitigate the effects of a disturbance event (e.g. flood) are referred to as refugia. Their occurrence in heavily impacted river systems is often limited, and their restoration rarely pursued. This paper presents the results of a combined laboratory and numerical modeling study to assess flood refugia availability to mobile aquatic org...

The spread of two‐dimensional numerical hydrodynamic tools for ecohydraulic applications allowed for the development of automatic habitat detection methods, adopted as predicting tools for river habitat analysis. These automatic approaches differ for the employed identification rules, such as preference curves, fuzzy rules and clustering methods. P...

New types of fish guidance structures with vertical curved bars and a subsequent bypass system represent a promising technical solution for the protection and guidance of downstream moving fish at run-of-river hydropower plants and water intakes. These so-called "curved-bar rack bypass systems" (CBR-BSs) function as a mechanical behavioral barrier...

In this paper, we present secondary current effects on the turbulence characteristics of supercritical narrow open channel flows over a smooth fixed bed. The main hydraulic parameters are low channel width to flow depth ratios varying between 1 and 2, and Froude numbers (F) ranging from 2 to 4. Detailed profiling of instantaneous streamwise and ver...

Impulse wave trains are generated by subaerial landslides, rockfalls, or avalanches impacting a water body. Especially in engineered reservoirs, the run-up of waves with small relative heights is critical due to the small freeboard between the still water level and the dam crest. To prevent overtopping, an accurate prediction of the maximum run-up...

Numerical models are used increasingly to tackle aerated flows for example in spillway design. However, these models are usually empirical and often lack thorough calibration. Herein a mixture model is calibrated with experimental data on uniform aerated flow from literature. A commercial code was used to solve the mixture Reynolds-averaged Navier–...

Historical reports and recent studies have shown that tsunamis can also occur in lakes where they may cause large damages and casualties. Among the historical reports are many tsunamis in Swiss lakes that have been triggered both by subaerial and subaqueous mass movements (SAEMM and SAQMM). In this study, we present a simplified classification of l...