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Hydraulic Modelling of Hydropeaking in Regulated Rivers
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0003-3408-9237
2023 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The role of hydropower is expected to change in the close future in the Nordic countries. In order to fulfill targets set by the Paris agreement, the reliance on low emission intermittent power production such as solar and wind power is likely to increase. This in turn means that the operating conditions of Nordic hydropower plants are expected to change to balance the volatility of intermittent power production. Hence, rapid flow fluctuations due to changes in power demand, so called hydropeaking, is likely to increase in the future. Hydropeaking is associated with many negative impacts on the reach downstream of the hydropower plant. It is with this background that the research consortium HydroFlex was created. One of the aims of HydroFlex is to investigate the effects of very high frequency hydropeaking on adjacent river reaches. In this work, several model scenarios involving high frequency hydropeaking in a bypass reach in the river Umeälven were investigated. The river dynamics was modeled using the solver Delft3D. By using LIDAR measurements in the winter, when the reach was mostly dry, it was possible to capture the bathymetry with high spatial resolution. A 2D model was then set up using the measured bathymetry and calibrated using eight pressure sensors placed along the reach. The transient response in the reach was then compared between the measured depth from the sensors and the model (Paper A). Once the calibration had been performed, the effects of an increase in hydropeaking frequency on the downstream reach, could be investigated. A hysteresis effect in the depth increase-decrease cycle was observed in both measurements and simulations. Additionally, high hydropeaking frequency led to a hydraulic stage in the river where steady state is never achieved (Paper B). This effect, and how it might affect downstream salmonid spawning areas, was then further investigated. It was observed that an increase in hydropeaking frequency could reduce the proportion of potential spawning areas in the downstream reach that would dry out. Furthermore, a general method of computing dewatering time for numerical models was provided. This method was then applied, in tandem with a stranding model, to investigate how different spill gate closing times affected salmonids propensity to stranding. The likelihood of stranding varied between species and life-stage. Moreover, the tendency of stranding decreased longitudinally downstream (Paper C). The findings of a hydraulic stage in (Paper B) merited further investigation. By investigating model scenarios, where the hydropeaking frequency varied between 10 and 80 flow changes per day, four different hydraulic stages that occur in the reach, were identified. A method of classifying the hydraulic stages was suggested. The identified hydraulic stages were: the dewatering stage, the alternating stage, the previously identified dynamic stage and lastly the uniform stage. The relation between the hydraulic stages and the hydropeaking frequency were then investigated using Fourier analysis. It was observed that the hydropeaking frequency is the dominant variable in the dynamic and uniform stages, while the alternating stage is more complex. Additionally, the dynamics of the stages could be predicted by performing a Fourier transform of one increase-decrease cycle. The Fourier spectrum could also be used as an alternative way of classifying the stage (Paper D). Numerical methods on their own is not a holistic tool to predict river flows, they require field measurements for calibration and validation. In (Paper E) an overview of the methods used in the field in this work is given. Moreover, a discussion on the limitations of 2D modeling for large scale river applications is presented.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2023. , p. 134
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-94342ISBN: 978-91-8048-225-7 (print)ISBN: 978-91-8048-226-4 (electronic)OAI: oai:DiVA.org:ltu-94342DiVA, id: diva2:1714378
Public defence
2023-03-21, E246, Luleå tekniska universitet, Luleå, 09:00 (English)
Opponent
Supervisors
Funder
EU, Horizon 2020Available from: 2022-11-29 Created: 2022-11-29 Last updated: 2023-02-22Bibliographically approved
List of papers
1. Inherent damping in a partially dry river
Open this publication in new window or tab >>Inherent damping in a partially dry river
2019 (English)In: E-proceedings of the 38th IAHR World Congress, International Association for Hydro-Enviroment Engineering and Research (IAHR) , 2019, p. 5091-5100Conference paper, Published paper (Refereed)
Abstract [en]

As intermittent power sources such as solar power and wind power gains traction in Scandinavia it is likely that the electricity production will become increasingly dependent on hydro power as a buffer in times of power deficit from intermittent power sources due to weather conditions. Rapid changes in hydro power demand can rapidly change the flow conditions in proximity to the power plant. This paper aims to model the transient behavior and quantify the inherent damping in a dry reach in proximity to the largest hydro power plant in Sweden, with respect to production. A two-dimensional model solving the Navier-Stokes equations with shallow water approximations was set up using the open-source solver Delft3D. The Manning numbers in the reach was calibrated with measured steady state water surface elevation data. The simulation data was then validated with transient water level measurements. The results show that it's possible to calibrate the Manning numbers using steady state water level measurements. The model also shows that it's possible to capture the inherent damping and more transient behavior using Delft3D. The results can be used to better model rivers without the need for resolving the upstream reach. The results can also be used for ecohydraulical applications where the transient behavior is important.

Place, publisher, year, edition, pages
International Association for Hydro-Enviroment Engineering and Research (IAHR), 2019
Series
Proceedings of the IAHR World Congress, ISSN 2521-7119, E-ISSN 2521-716X
Keywords
Ecohydraulics, Delft3D, Damping, Manning number, Damping
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-76457 (URN)10.3850/38WC092019-0281 (DOI)2-s2.0-85087453963 (Scopus ID)
Conference
38th IAHR World Congress, 1-6 September, 2019, Panama City, Panama
Available from: 2019-10-21 Created: 2019-10-21 Last updated: 2024-03-07Bibliographically approved
2. Case Study of Transient Dynamics in a Bypass Reach
Open this publication in new window or tab >>Case Study of Transient Dynamics in a Bypass Reach
2020 (English)In: Water, E-ISSN 2073-4441, Vol. 12, no 6, article id 1585Article in journal (Refereed) Published
Abstract [en]

The operating conditions of Nordic hydropower plants are expected to change in the coming years to work more in conjunction with intermittent power production, causing more frequent hydropeaking events. Hydropeaking has been shown to be detrimental to wildlife in the river reaches downstream of hydropower plants. In this work, we investigate how different possible future hydropeaking scenarios affect the water surface elevation dynamics in a bypass reach in the Ume River in northern Sweden. The river dynamics has been modeled using the open-source solver Delft3D. The numerical model was validated and calibrated with water-surface-elevation measurements. A hysteresis effect on the water surface elevation, varying with the downstream distance from the spillways, was seen in both the simulated and the measured data. Increasing the hydropeaking rate is shown to dampen the variation in water surface elevation and wetted area in the most downstream parts of the reach, which could have positive effects on habitat and bed stability compared to slower rates in that region.

Place, publisher, year, edition, pages
MDPI, 2020
Keywords
inherent damping, hydropeaking, river dynamics, hydraulic modeling, delft3d
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-79175 (URN)10.3390/w12061585 (DOI)000550865600001 ()2-s2.0-85087451637 (Scopus ID)
Projects
HydroFlex
Note

Validerad;2020;Nivå 2;2020-07-15 (alebob)

Available from: 2020-06-04 Created: 2020-06-04 Last updated: 2023-08-28Bibliographically approved
3. Modelling the downstream longitudinal effects of frequent hydropeaking on the spawning potential and stranding susceptibility of salmonids
Open this publication in new window or tab >>Modelling the downstream longitudinal effects of frequent hydropeaking on the spawning potential and stranding susceptibility of salmonids
Show others...
2021 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 796, article id 148999Article in journal (Refereed) Published
Abstract [en]

Hydropower plant operating conditions are expected to change to be more in tandem with intermittent power production so as to meet the requirements of the Paris Agreement, which in turn may negatively impact ecological conditions downstream of the hydropower plants. The current study investigates how highly flexible hydropower operating conditions may impact several salmonid species (European grayling, Atlantic salmon and brown trout) in the River Umeälven, a major river in northern Sweden; specifically, how changes in hydropeaking frequency may affect the area of the downstream watercourse that is hydraulically suitable for spawning (potential spawning area) and how changes in spill gate closing time may affect the propensity to stranding. River hydrodynamics were modeled using the open-source solver Delft3D, with a range of hydropeaking frequencies (from 10 to 60 starts and stops per day) and a range of spill gate closing times from (1–30 min). Increasing the hydropeaking frequency caused a reduction in potential spawning area, but also a reduction in dewatering of potential spawning area at low flows. Increasing spill gate closing time caused a decrease in propensity to stranding. Effects were dependent on both species and life-stage, and declined longitudinally with distance downstream from the spillway outlet. The modelling approach used here provides an effective method for predicting likely outcomes of flexible hydropower operating conditions, taking into account fish species and life-stages present and watercourse characteristics.

Place, publisher, year, edition, pages
Elsevier, 2021
Keywords
Hydropeaking, Spawning habitat, Salmonids, Modelling, Dewatering
National Category
Fluid Mechanics and Acoustics Ecology
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-86377 (URN)10.1016/j.scitotenv.2021.148999 (DOI)000697347800016 ()34280623 (PubMedID)2-s2.0-85110532565 (Scopus ID)
Funder
EU, Horizon 2020, 764011
Note

Validerad;2021;Nivå 2;2021-07-26 (beamah)

Available from: 2021-07-15 Created: 2021-07-15 Last updated: 2022-11-29Bibliographically approved
4. Hydraulic classification of hydropeaking stages in a river reach
Open this publication in new window or tab >>Hydraulic classification of hydropeaking stages in a river reach
2023 (English)In: Rivers Research and Applications: an international journal devoted to river research and management, ISSN 1535-1459, E-ISSN 1535-1467, Vol. 39, no 4, p. 692-702Article in journal (Refereed) Published
Abstract [en]

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, high-frequency 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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
delft3d, Fourier analysis, hydraulic stage, hydropeaking, hydropeaking frequency
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-94340 (URN)10.1002/rra.4098 (DOI)000907519300001 ()2-s2.0-85145677139 (Scopus ID)
Funder
EU, Horizon 2020, 764011
Note

Validerad;2023;Nivå 2;2023-07-21 (sofila);

This article has previously appeared as a manuscript in a thesis.

Available from: 2022-11-29 Created: 2022-11-29 Last updated: 2023-07-21Bibliographically approved
5. Ecohydraulical Applications and Limitations of Calibrated Numerical 2D Models
Open this publication in new window or tab >>Ecohydraulical Applications and Limitations of Calibrated Numerical 2D Models
2022 (English)In: Proceedings of the 39th IAHR World Congress: From Snow To Sea / [ed] Miguel Ortega-Sánchez, International Association for Hydro-Environment Engineering and Research (IAHR) , 2022, p. 1557-1564Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
International Association for Hydro-Environment Engineering and Research (IAHR), 2022
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-94339 (URN)10.3850/IAHR-39WC2521711920221796 (DOI)2-s2.0-85176466987 (Scopus ID)
Conference
39th IAHR World Congress, Granada, Spain, June 19-24, 2022
Funder
EU, Horizon 2020, 764011
Note

ISBN for host publication: 978-90-832612-1-8

Available from: 2022-11-29 Created: 2022-11-29 Last updated: 2023-12-20Bibliographically approved

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Citation style
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  • modern-language-association-8th-edition
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  • en-GB
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Output format
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