Case Study of Transient Dynamics in a Bypass Reach

Burman, Anton; Andersson, Anders G.; Hellström, J. Gunnar I.; Angele, Kristian

doi:10.3390/w12061585

Cited by 5 publications

(12 citation statements)

References 25 publications

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“…Similarly, it is observed that frequent sub-daily ramping dampens the dewatering effect far downstream in the river as the river starts rising again before the previous stop has reached the minimum level. A similar effect was seen by Burman et al (2020) running similar hydropeaking studies in a bypass reach in the Ume river in Sweden. The downstream effect of a hydropeaking operation in a river will be closely related to the ramping rate and longitudinal dampening in the river due to the morphology which has a large effect on dewatering rates (Hauer et al, 2014;Hauer et al, 2017).…”

Section: Discussionsupporting

confidence: 73%

Mitigation of environmental effects of frequent flow ramping scenarios in a regulated river

Alfredsen

Juárez-Goméz

Kenawi

et al. 2022

Front. Environ. Sci.

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In the transition to a society based on renewable energy, flexibility is important in balancing the energy supply as more intermittent sources like wind and solar are included in the energy mix. The storage-based hydropower systems are a renewable energy source that provides the needed flexibility since a hydropower plant can be started and stopped in minutes, and the reservoirs provide stored energy that can be utilized when the demand arises. Thereby, the hydropower plants can balance the variability in other energy sources, e.g., when there is no wind or when solar input is low. This need for increased flexibility has led research toward new hydropower turbines to provide larger ramping rates, more frequent starts and stops, and other system services. A possible drawback of the ramping operation of hydropower plants (often termed “hydropeaking”) are the adverse effects on the environment in receiving water bodies downstream of the power plant outlet, particularly when the hydropower outlets are in rivers. Rapid changes in flow can lead to stranding of fish and other biota during the shutdown of turbines and flushing of biota during the start of turbines. These effects can also be caused by other sudden episodes of water withdrawal, such as during accidental turbine shutdowns. The main objective of this study is to describe a method of designing the necessary volume of water required to mitigate a fast ramping turbine, and present the effect this has on the downstream river reach. We used a 2D hydraulic model to find the areas affected by hydropeaking operation and, furthermore, to define areas with a faster ramping rate than 13 cm/h which is used as a limit in Norwegian guidelines. Based on this, we developed a ramping regime that would prevent fast dewatering of critical areas and provide this as a basis for mitigating the effects of fast dewatering in the downstream river (River Nidelva in Norway was used as a test case). Furthermore, the effect of increasing the frequency of start–stop cycles was studied, and the proposed mitigation was evaluated for the new operational regime.

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Section: Discussionsupporting

confidence: 73%

Mitigation of environmental effects of frequent flow ramping scenarios in a regulated river

Alfredsen

Juárez-Goméz

Kenawi

et al. 2022

Front. Environ. Sci.

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“…An overview of the study reach in the proximity of Stornorrfors can be seen in Figure 1. The water level dynamics of the study reach was calibrated and validated for a hydropeaking cycle of 21 m 3 /s → 50 m 3 /s → 21 m 3 /s with a 5‐min flow change time in a previous study (Burman et al, 2020). The well‐defined flow conditions as well as validation data from previous work (Andersson et al, 2012; Angele & Andersson, 2018; Burman et al, 2020) performed in the reach made it a suitable study site.…”

Section: Methodsmentioning

confidence: 99%

“…One such effect, the hysteresis in the increase-decrease cycle causes, likely adds additional spikes to the spectrum. The hysteresis in turn depends on 3D effects, such as turbulence, as well as longitudinal distance from the spillways (Burman et al, 2020).…”

Section: Fourier Analysismentioning

confidence: 99%

“…The risk of dewatering for potential salmonid spawning habitat was reduced for high‐frequency hydropeaking (Burman et al, 2021). Furthermore, the magnitude of the water level variation reduced as the hydropeaking frequency increased (Burman, Andersson, Hellström, & Angele, 2020), indicating that very high‐frequency hydropeaking might reduce dewatering in the downstream parts of the reach. Hence, it is of interest to further investigate the role of hydropeaking frequency and how it affects the hydrodynamics in the downstream reach.…”

Section: Introductionmentioning

confidence: 99%

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Hydraulic classification of hydropeaking stages in a river reach

Burman

Andersson

Hellström

2023

River Research & Apps

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Hydropower is an important tool in the struggle for low-emission power production.In the Nordic countries, hydropower operating conditions are expected to change and work more in conjunction with intermittent power production. This in turn might increase the amount of hydropeaking events in the reaches downstream of hydropower plants. The current work investigates the influence of highly flexible, highfrequency hydropeaking on the hydrodynamics in the downstream reach. By quantifying four different dynamic stages in the study reach, the influence of the hydropeaking frequencies was investigated in the bypass reach of the Stornorrfors hydropower plant in the river Umeälven in northern Sweden. The hydrodynamics in the study reach were numerically modelled using the open source solver Delft3D.Eight different highly flexible future hydropeaking scenarios, varying from 12 to 60 flow changes per day, were considered. A method for identifying four hydropeaking stages-dewatering, dynamic, alternating and uniform -was introduced. The hydropeaking frequency directly decided the stage in most of the study reach.Furthermore, a Fourier analysis showed a significant difference between the stages and their corresponding power spectra. The classification of stages put forward in this work provides a novel, simple method to investigate the hydrodynamics due to hydropeaking in a river reach.

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“…To assess the influence of the flow rate in the old river channel on the preferences for the fish in a biotope perspective, a biological and hydraulic field investigation was made, Angele [2]. A 2D transient, hydraulic model using Hydraulic Engineering Center River Analysis System (HEC-RAS) was also conducted, see also Burman [10], in which different flow scenarios were tested. The conclusion was that the fish preferences in terms of local water velocity and water depth were optimized for a flow rate of 10 m 3 /s in the old river channel.…”

Section: Figurementioning

confidence: 99%

A Contraction Based Solution for the Improvement of Fish Ladder Attraction Flow

Angele¹,

Andreasson²,

Forssen³

et al. 2021

AJWSE

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A new, potentially cost efficient, concept for improving the attraction flow to a fish ladder has been investigated in a case study. For the upstream migrating Atlantic salmon to reach the fish ladder and by-pass the case study hydropower plant, it must be able to localize the attraction flow where it enters the main flow from the tailrace of the hydropower plant in the so-called confluence area. Here the comparatively small and limited attraction flow from the old river channel must be improved in order to be able compete with the substantially larger main flow. The objective of the present study is to investigate the feasibility of a new concept for further improvement of the attraction flow using guiding walls forming a contraction channel. Field measurements were performed tracing tagged fish in the confluence area downstream of the case study hydropower plant in order to understand the movement pattern of the fish. Based on the results, and results from bathymetry measurements in the same area, a physical scale model was constructed where it was experimentally demonstrated that it is hydraulically feasible to construct guiding walls, forming a contraction, which accelerate the attraction flow and generate a concentrated turbulent jet with a higher velocity, while keeping the flow rate unchanged. The attraction flow penetrates about half-way (70 m) into the main flow and reaches the position where most fish are positioned according to fish position measurements and therefore potentially has a good ability to attract upstream migrating fish. There is no negative impact on the water level in the confluence area and thereby not on electricity production. It was shown that the results can be scaled up to prototype conditions and the strategy can presumably be generalized to similar flow situations, existing at other hydropower plants, allowing for improved upstream fish migration in coexistence with a sound hydropower production.

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Case Study of Transient Dynamics in a Bypass Reach

Cited by 5 publications

References 25 publications

Mitigation of environmental effects of frequent flow ramping scenarios in a regulated river

Mitigation of environmental effects of frequent flow ramping scenarios in a regulated river

Hydraulic classification of hydropeaking stages in a river reach

A Contraction Based Solution for the Improvement of Fish Ladder Attraction Flow

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