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Prof. Dr. Knut Alfredsen
Department of Hydraulic and Environmental Engineering, Norwegian University of Science and Technology, S.P.Andersensvei 5, 7491 Trondheim, Norway

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0 water resources management
0 Hydrological model
0 Lakes and Rivers
0 Mitigation measures
0 River regulations

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Hydrological model
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water resources management
Hydropower systems

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Encyclopedia
Published: 29 July 2021 in Reference Module in Earth Systems and Environmental Sciences
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Snow and ice plays an important role in hydropower planning and operation in cold climates. Demand for production is usually highest in the season when inflow is the lowest due to snow accumulation, and assessment of the snow storage and snow melt is crucial for planning of reservoir operation to meet demand in low inflow periods. The formation of ice in rivers and reservoirs is important for the design of hydropower structures and for operational and environmental aspects of hydropower in cold regions.

ACS Style

Knut Alfredsen; Oddbjørn Bruland. Hydropower in Cold Regions. Reference Module in Earth Systems and Environmental Sciences 2021, 1 .

AMA Style

Knut Alfredsen, Oddbjørn Bruland. Hydropower in Cold Regions. Reference Module in Earth Systems and Environmental Sciences. 2021; ():1.

Chicago/Turabian Style

Knut Alfredsen; Oddbjørn Bruland. 2021. "Hydropower in Cold Regions." Reference Module in Earth Systems and Environmental Sciences , no. : 1.

Journal article
Published: 07 July 2021 in Water
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Floods are among the most damaging of natural disasters, and flood events are expected to increase in magnitude and frequency with the effects of climate change and changes in land use. As a consequence, much focus has been placed on the engineering of structural flood mitigation measures in rivers. Traditional flood protection measures, such as levees and dredging of the river channel, threaten floodplains and river ecosystems, but during the last decade, sustainable reconciliation of freshwater ecosystems has increased. However, we still find many areas where these traditional measures are proposed, and it is challenging to find tools for evaluation of different measures and quantification of the possible impacts. In this paper, we focus on the river Lærdal in Norway to (i) present the dilemma between traditional flood measures and maintaining river ecosystems and (ii) quantify the efficiency and impact of different solutions based on 2D hydraulic models, remote sensing data, economics, and landscape metrics. Our results show that flood measures may be in serious conflict with environmental protection and legislation to preserve biodiversity and key nature types.

ACS Style

Ana Juárez; Knut Alfredsen; Morten Stickler; Ana Adeva-Bustos; Rodrigo Suárez; Sonia Seguín-García; Bendik Hansen. A Conflict between Traditional Flood Measures and Maintaining River Ecosystems? A Case Study Based upon the River Lærdal, Norway. Water 2021, 13, 1884 .

AMA Style

Ana Juárez, Knut Alfredsen, Morten Stickler, Ana Adeva-Bustos, Rodrigo Suárez, Sonia Seguín-García, Bendik Hansen. A Conflict between Traditional Flood Measures and Maintaining River Ecosystems? A Case Study Based upon the River Lærdal, Norway. Water. 2021; 13 (14):1884.

Chicago/Turabian Style

Ana Juárez; Knut Alfredsen; Morten Stickler; Ana Adeva-Bustos; Rodrigo Suárez; Sonia Seguín-García; Bendik Hansen. 2021. "A Conflict between Traditional Flood Measures and Maintaining River Ecosystems? A Case Study Based upon the River Lærdal, Norway." Water 13, no. 14: 1884.

Journal article
Published: 28 April 2021 in Water
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Fish swimming performance is strongly influenced by flow hydrodynamics, but little is known about the relation between fine-scale fish movements and hydrodynamics based on in-situ investigations. In the presented study, we validated the etho-hydraulic fish swimming direction model presented in the River Mandal from Southern Norway, using similar behavioral and hydraulic data on salmon smolts from the River Orkla in Central Norway. The re-parametrized model explained the variation of the swimming direction of fish in the Orkla system in same degree as the original model performed in the Mandal system (R2: 84% in both cases). The transferability of the model when using it from one river to predict swimming direction in the other river was lower (R2: 21% and 26%), but nevertheless relatively high given that the two localities differed in hydraulic conditions. The analyses thus provide support for the fact that the identified hydraulic parameters and their interaction affected smolt behavior in a similar way at the two sites, but that local parametrization of the base model is required. The developed etho-hydraulic models can provide important insights into fish behavior and fish migration trajectories and can be developed into prediction models important for the future development of behavioral downstream migration solutions.

ACS Style

Marcell Szabo-Meszaros; Ana Silva; Kim Bærum; Henrik Baktoft; Knut Alfredsen; Richard Hedger; Finn Økland; Karl Gjelland; Hans-Petter Fjeldstad; Olle Calles; Torbjørn Forseth. Validation of a Swimming Direction Model for the Downstream Migration of Atlantic Salmon Smolts. Water 2021, 13, 1230 .

AMA Style

Marcell Szabo-Meszaros, Ana Silva, Kim Bærum, Henrik Baktoft, Knut Alfredsen, Richard Hedger, Finn Økland, Karl Gjelland, Hans-Petter Fjeldstad, Olle Calles, Torbjørn Forseth. Validation of a Swimming Direction Model for the Downstream Migration of Atlantic Salmon Smolts. Water. 2021; 13 (9):1230.

Chicago/Turabian Style

Marcell Szabo-Meszaros; Ana Silva; Kim Bærum; Henrik Baktoft; Knut Alfredsen; Richard Hedger; Finn Økland; Karl Gjelland; Hans-Petter Fjeldstad; Olle Calles; Torbjørn Forseth. 2021. "Validation of a Swimming Direction Model for the Downstream Migration of Atlantic Salmon Smolts." Water 13, no. 9: 1230.

Review paper
Published: 17 March 2021 in River Research and Applications
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Water temperatures control life histories and diversity of aquatic species. Hydropower regulation, particularly in high head systems, alters natural water temperature regimes, which may have profound and long‐term impacts on aquatic environments. Temperatures in by‐pass sections and reaches affected by residual/environmental minimum flows fluctuate more than in natural flow regimes, driven more by influence of air temperatures. Reaches downstream of power plant outlets tend to become warmer in winter and colder in summer, driven by stratification behind the reservoir dam. In hydro‐peaked systems high‐low temperature effects may thus be aggravated. We review alterations of hydropower to natural thermal regimes, impacts on key organisms in terms of survival, development and behavioral thresholds, and potential mitigation measures, with focus on Atlantic salmon and brown trout in high northern latitude stream systems. Previous syntheses have focused mainly on flow changes and ecological impacts. Temperature effects may not always be correlated with flow changes, although there are some unique challenges with temperature changes in far northern latitudes, for example, related to the seasonal and colder climates. To help knowledge‐based management and identify potential knowledge gaps, we review how hydropower regulation may impact seasonal water temperatures, what impacts changes to stream system temperature regimes may have to key organisms, for example, Atlantic salmon and brown trout, and what adaptations and behavioral variations they may exhibit to respond to changed temperature regimes, and finally what good practices can be recommended for mitigating temperature impacts. This synthesis indicates that there are impacts to the fish and their supporting food webs, in particular related to growth and development, and the potential for negative impacts seems higher, and better studied, than positive impacts in northern river systems. Some of these impacts may be modified by directed hydropower regulation practices, but here effect studies and knowledge are limited.

ACS Style

Jan Heggenes; Morten Stickler; Knut Alfredsen; John E. Brittain; Ana Adeva‐Bustos; Ari Huusko. Hydropower‐driven thermal changes, biological responses and mitigating measures in northern river systems. River Research and Applications 2021, 37, 743 -765.

AMA Style

Jan Heggenes, Morten Stickler, Knut Alfredsen, John E. Brittain, Ana Adeva‐Bustos, Ari Huusko. Hydropower‐driven thermal changes, biological responses and mitigating measures in northern river systems. River Research and Applications. 2021; 37 (5):743-765.

Chicago/Turabian Style

Jan Heggenes; Morten Stickler; Knut Alfredsen; John E. Brittain; Ana Adeva‐Bustos; Ari Huusko. 2021. "Hydropower‐driven thermal changes, biological responses and mitigating measures in northern river systems." River Research and Applications 37, no. 5: 743-765.

Journal article
Published: 04 February 2021 in Animal Biotelemetry
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Background Behaviour of potential host fish during chemical treatment against the ectoparasite Gyrodactylus salaris is a vital factor in designing treatment strategies, evaluating risk factors and establishing insights into previously failed treatments. The effectiveness of any chemical treatment may be compromised if fish either are forced to, or seek out actively, areas of the river where the water quality is less affected by the chemicals. The aim of this study was to develop and apply an acoustic fish tag for fish localization with sensors for in situ measurement of water conductivity and temperature to investigate fish behaviour before, during and after an aluminium (Al) treatment. The sensor tag allowed discrimination between water qualities, and thereby quantification of exposure to treatment water. Findings Adult Atlantic salmon and anadromous brown trout from river Lærdalselva were tagged with external conductivity transmitters and followed daily by a network of passive receivers and by manual tracking 1 week ahead of treatment, during a 2-week aluminium (Al) treatment period and one week after an Al treatment. The results show no avoidance behaviour related to the Al treatment and most of the fish exhibited a behaviour during the treatment that did not differ significantly from the behaviour observed before or after the treatment. Data collected from the tags showed that the fish experienced increased conductivity during Al administration, suggesting successful exposure to treatment water. The tag gave verifiable environmental information and functioned well in the turbulent and acoustically demanding river environment, albeit with variable detection range. Conclusions The conductivity and temperature tag provided novel data on fish behaviour and exposure during the Al treatment period. Results show that fish exhibit normal behaviour during this period and no avoidance response can be detected in the collected data.

ACS Style

Knut Tore Alfredsen; Henning Andre Urke; Torstein Kristensen; Marte Kvakland; Aage Gronningsater; Anders Gjørwad Hagen; Jo Arve Alfredsen. An acoustic sensor transmitter for in situ assessment of water quality and fish behaviour during chemical treatment of a parasite-infected river system: tag design and practical use. Animal Biotelemetry 2021, 9, 1 -14.

AMA Style

Knut Tore Alfredsen, Henning Andre Urke, Torstein Kristensen, Marte Kvakland, Aage Gronningsater, Anders Gjørwad Hagen, Jo Arve Alfredsen. An acoustic sensor transmitter for in situ assessment of water quality and fish behaviour during chemical treatment of a parasite-infected river system: tag design and practical use. Animal Biotelemetry. 2021; 9 (1):1-14.

Chicago/Turabian Style

Knut Tore Alfredsen; Henning Andre Urke; Torstein Kristensen; Marte Kvakland; Aage Gronningsater; Anders Gjørwad Hagen; Jo Arve Alfredsen. 2021. "An acoustic sensor transmitter for in situ assessment of water quality and fish behaviour during chemical treatment of a parasite-infected river system: tag design and practical use." Animal Biotelemetry 9, no. 1: 1-14.

Journal article
Published: 07 September 2020 in Sustainability
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Repeat spawners constitute an important component of Atlantic salmon populations, but survival of post-spawning individuals (kelts) are often compromised by anthropogenic structures such as hydropower plants (HPPs). Potential effects of HPPs include migration delays and associated increased energy depletion, which potentially results in increased overall mortality. We combined a detailed 3D hydraulic model with high-resolution 3D tracking of tagged kelts (length 73–104 cm) to obtain estimates of kelt movement through water. These estimates were then used in an energetics model to estimate hourly energy expenditure while negotiating the HPP area. Hourly kelt energy expenditure varied between 0.8 and 10.1 kJ × h−1 and was dependent on kelt length. Degree of additional energy depletion can amount to several percent of remaining energy content (our study indicates 4–5 percentage points) potentially leading to reduced post-spawning survival. In turn, this can nullify the iteroparous breeding strategy and jeopardize long-term stability and persistence of Atlantic salmon populations inhabiting HPP rivers.

ACS Style

Henrik Baktoft; Karl Gjelland; Marcell Szabo-Meszaros; Ana Silva; Milan Riha; Finn Økland; Knut Alfredsen; Torbjørn Forseth. Can Energy Depletion of Wild Atlantic Salmon Kelts Negotiating Hydropower Facilities Lead to Reduced Survival? Sustainability 2020, 12, 7341 .

AMA Style

Henrik Baktoft, Karl Gjelland, Marcell Szabo-Meszaros, Ana Silva, Milan Riha, Finn Økland, Knut Alfredsen, Torbjørn Forseth. Can Energy Depletion of Wild Atlantic Salmon Kelts Negotiating Hydropower Facilities Lead to Reduced Survival? Sustainability. 2020; 12 (18):7341.

Chicago/Turabian Style

Henrik Baktoft; Karl Gjelland; Marcell Szabo-Meszaros; Ana Silva; Milan Riha; Finn Økland; Knut Alfredsen; Torbjørn Forseth. 2020. "Can Energy Depletion of Wild Atlantic Salmon Kelts Negotiating Hydropower Facilities Lead to Reduced Survival?" Sustainability 12, no. 18: 7341.

Journal article
Published: 01 April 2020 in Hydrology Research
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ACS Style

Kolbjørn Engeland; Knut Alfredsen. Hydrology and water resources management in a changing world. Hydrology Research 2020, 51, 143 -145.

AMA Style

Kolbjørn Engeland, Knut Alfredsen. Hydrology and water resources management in a changing world. Hydrology Research. 2020; 51 (2):143-145.

Chicago/Turabian Style

Kolbjørn Engeland; Knut Alfredsen. 2020. "Hydrology and water resources management in a changing world." Hydrology Research 51, no. 2: 143-145.

Editorial
Published: 19 September 2019 in Water
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Hydraulic habitat simulation models were designed for the quantitative determination of environmental flows that consider the needs of aquatic fauna in rivers and streams. In the past 50 years, the modeling techniques were significantly developed, but expectations associated with model utility also increased. Nowadays, the tools are expected to be applicable across a range of spatial and temporal scales and to protect entire aquatic communities, while being inexpensive as well as easy to use in administrative and legal environments. Addressing these challenges is the focus of this volume. We invited papers that present recent developments in habitat modeling, supported by real life case studies. The submitted papers well represent the wide applicability of habitat simulation models, allowing us to address both ends of river management requirements: the ability to address very detailed site specific issues as well as the ability to address the coarse scale applications necessary in regional management.

ACS Style

Piotr Parasiewicz; Paweł Prus; Christos Theodoropoulos; Knut Alfredsen; Mikołaj Adamczyk; Claudio Comoglio; Paolo Vezza. Environmental Flows Determination and Monitoring with Hydraulic Habitat Models—Pushing the Boundaries of Habitat Models Application. Water 2019, 11, 1950 .

AMA Style

Piotr Parasiewicz, Paweł Prus, Christos Theodoropoulos, Knut Alfredsen, Mikołaj Adamczyk, Claudio Comoglio, Paolo Vezza. Environmental Flows Determination and Monitoring with Hydraulic Habitat Models—Pushing the Boundaries of Habitat Models Application. Water. 2019; 11 (9):1950.

Chicago/Turabian Style

Piotr Parasiewicz; Paweł Prus; Christos Theodoropoulos; Knut Alfredsen; Mikołaj Adamczyk; Claudio Comoglio; Paolo Vezza. 2019. "Environmental Flows Determination and Monitoring with Hydraulic Habitat Models—Pushing the Boundaries of Habitat Models Application." Water 11, no. 9: 1950.

Journal article
Published: 27 May 2019 in Environmental Modelling & Software
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This study presents a dynamic forecast combination approach adapted to incorporate multiple sources of precipitation. Dynamic combination serves to utilise the varying merit each data source exhibits with time. The dynamic model combination framework presented merges a nonparametric k-nearest neighbour (k-nn) estimation of radar precipitation with Thin Plate Spline (TPS) interpolated gauge precipitation. Since air temperature is an essential variable to discriminate the phase of the precipitation in cold climates, this study uses radar precipitation and air temperature as the two variables in the dynamic combination algorithm. The merging of k-nn and TPS estimates is shown to reduce the RMSE by 25% compared to the original radar precipitation rates. The usefulness of air temperature is found not to be as significant in the combination as it is in the formulation of the nonparametric radar precipitation fields for cold incident temperatures.

ACS Style

Kuganesan Sivasubramaniam; Ashish Sharma; Knut Alfredsen. Merging radar and gauge information within a dynamical model combination framework for precipitation estimation in cold climates. Environmental Modelling & Software 2019, 119, 99 -110.

AMA Style

Kuganesan Sivasubramaniam, Ashish Sharma, Knut Alfredsen. Merging radar and gauge information within a dynamical model combination framework for precipitation estimation in cold climates. Environmental Modelling & Software. 2019; 119 ():99-110.

Chicago/Turabian Style

Kuganesan Sivasubramaniam; Ashish Sharma; Knut Alfredsen. 2019. "Merging radar and gauge information within a dynamical model combination framework for precipitation estimation in cold climates." Environmental Modelling & Software 119, no. : 99-110.

Journal article
Published: 29 March 2019 in Journal of Hydrology
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Streamflow data is important for studies of water resources and flood management, but an inherent problem is that many catchments of interest are ungauged. The lack of data is particularly the case for small catchments, where flow data with high temporal resolution is needed. This paper presents an analysis of regionalizing parameters of the Distance Distribution Dynamics (DDD) rainfall-runoff model for predicting hourly flows at small-ungauged rural catchments. The performance of the model with hourly time resolution has been evaluated (calibrated and validated) for 41 small gauged catchments in Norway (areas from 1 km2 – 50km2). The model parameters needing regionalization have been regionalized using three different methods: multiple regression, physical similarity (single-donor and pooling-group based methods), and a combination of the two methods. Seven independent catchments, which are not used in the evaluation, are used for validation of the regionalization methods. All the three methods (the multiple regression, pooling-group, and combined methods) perform satisfactorily (0.5 ≤ KGE < 0.75). The combined method (which combines multiple regression and pooling-group) performed slightly better than the other methods. Some model parameters, namely those describing recession characteristics, estimated by the regionalization methods, appear to be a better choice than those estimated locally from short period of hydro-meteorological data for some test catchments. The single-donor method did not perform satisfactorily. The satisfactory performance of the combined method shows that regionalization of DDD model parameters is possible by combining multiple regression and physical similarity methods.

ACS Style

Aynalem Tassachew Tsegaw; Knut Alfredsen; Thomas Skaugen; Tone M. Muthanna. Predicting hourly flows at ungauged small rural catchments using a parsimonious hydrological model. Journal of Hydrology 2019, 573, 855 -871.

AMA Style

Aynalem Tassachew Tsegaw, Knut Alfredsen, Thomas Skaugen, Tone M. Muthanna. Predicting hourly flows at ungauged small rural catchments using a parsimonious hydrological model. Journal of Hydrology. 2019; 573 ():855-871.

Chicago/Turabian Style

Aynalem Tassachew Tsegaw; Knut Alfredsen; Thomas Skaugen; Tone M. Muthanna. 2019. "Predicting hourly flows at ungauged small rural catchments using a parsimonious hydrological model." Journal of Hydrology 573, no. : 855-871.

Journal article
Published: 12 March 2019 in Sustainability
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Despite that hydromorphological restoration projects have been implemented since the 1940s, the key to improve the effectiveness of future restoration measures remains a challenge. This is in part related to the lack of adequate aims and objectives together with our limitations in understanding the effects on the physical habitat and ecosystems from interventions. This study shows the potential of using remote sensing techniques combined with hydraulic modelling to evaluate the success of physical restoration measures using habitat suitability as a quantifiable objective. Airborne light detection and ranging (LiDAR) was used to build a high-resolution two-dimensional model for Ljungan River, Sweden, using HEC-RAS 5.0. Two types of instream restoration measures were simulated according to the physical measures carried out in the river to improve salmonid habitat: (a) stones and rocks were moved from the bank sides to the main channel, and (b) a concrete wall was broken to open two channels to connect a side channel with the main river. Results showed that the hydraulic model could potentially be used to simulate the hydraulic conditions before and after instream modifications were implemented. A general improvement was found for the potential suitable habitat based on depth, velocity and shear stress values after the instream measures.

ACS Style

Ana Adeva-Bustos; Knut Alfredsen; Hans-Petter Fjeldstad; Kenneth Ottosson. Ecohydraulic Modelling to Support Fish Habitat Restoration Measures. Sustainability 2019, 11, 1500 .

AMA Style

Ana Adeva-Bustos, Knut Alfredsen, Hans-Petter Fjeldstad, Kenneth Ottosson. Ecohydraulic Modelling to Support Fish Habitat Restoration Measures. Sustainability. 2019; 11 (5):1500.

Chicago/Turabian Style

Ana Adeva-Bustos; Knut Alfredsen; Hans-Petter Fjeldstad; Kenneth Ottosson. 2019. "Ecohydraulic Modelling to Support Fish Habitat Restoration Measures." Sustainability 11, no. 5: 1500.

Journal article
Published: 24 January 2019 in Water
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Extreme, short-duration fluctuations caused by hydropeaking occurs when hydropower is regulated to cover demand peaks in the electricity market. Such rapid dewatering processes may have a high impact on the downstream biological conditions, particularly related to stranding of fish and other species. The present work analyzes these fluctuations using a two-dimensional unsteady hydraulic modelling approach for quantification of two important hydro-morphological factors on fish stranding risk: the variation in wetted area and the dewatering ramping rate. This approach was applied on the two-kilometer-long reach of Storåne downstream of the Hol 1 power plant, where topo bathymetric LiDAR (Light Detection and Ranging) data was available providing a high-resolution digital elevation model. Based on this model, hydraulic conditions could be simulated in high detail allowing for an accurate assessment of the hydro morphological factors. Results show the dried area distribution at different flows and dewatering ramping rates. The attenuation of the water level fluctuation due to the damping effect along the river reach controls the dewatering rate. We recommend an alternative scenario operation which can reduce the impact of the peaking operation and estimate the operational mitigation cost. We find that the modelling based on the fine resolution grid provides new opportunities in assessing effects of hydropower regulations on the ecosystem.

ACS Style

Ana Juárez; Ana Adeva-Bustos; Knut Alfredsen; Bjørn Otto Dønnum. Performance of A Two-Dimensional Hydraulic Model for the Evaluation of Stranding Areas and Characterization of Rapid Fluctuations in Hydropeaking Rivers. Water 2019, 11, 201 .

AMA Style

Ana Juárez, Ana Adeva-Bustos, Knut Alfredsen, Bjørn Otto Dønnum. Performance of A Two-Dimensional Hydraulic Model for the Evaluation of Stranding Areas and Characterization of Rapid Fluctuations in Hydropeaking Rivers. Water. 2019; 11 (2):201.

Chicago/Turabian Style

Ana Juárez; Ana Adeva-Bustos; Knut Alfredsen; Bjørn Otto Dønnum. 2019. "Performance of A Two-Dimensional Hydraulic Model for the Evaluation of Stranding Areas and Characterization of Rapid Fluctuations in Hydropeaking Rivers." Water 11, no. 2: 201.

Journal article
Published: 22 November 2018 in Scientific Reports
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Quantifying short-term changes in river flow is important in understanding the environmental impacts of hydropower generation. Energy markets can change rapidly and energy demand fluctuates at sub-daily scales, which may cause corresponding changes in regulated river flow (hydropeaking). Due to increasing use of renewable energy, in future hydropower will play a greater role as a load balancing power source. This may increase current hydropeaking levels in Nordic river systems, creating challenges in maintaining a healthy ecological status. This study examined driving forces for hydropeaking in Nordic rivers using extensive datasets from 150 sites with hourly time step river discharge data. It also investigated the influence of increased wind power production on hydropeaking. The data revealed that hydropeaking is at high levels in the Nordic rivers and have seen an increase over the last decade and especially over the past few years. These results indicate that increased building for renewable energy may increase hydropeaking in Nordic rivers.

ACS Style

Faisal Bin Ashraf; Ali Torabi Haghighi; Joakim Riml; Knut Alfredsen; Jarkko J. Koskela; Bjørn Kløve; Hannu Marttila. Changes in short term river flow regulation and hydropeaking in Nordic rivers. Scientific Reports 2018, 8, 17232 .

AMA Style

Faisal Bin Ashraf, Ali Torabi Haghighi, Joakim Riml, Knut Alfredsen, Jarkko J. Koskela, Bjørn Kløve, Hannu Marttila. Changes in short term river flow regulation and hydropeaking in Nordic rivers. Scientific Reports. 2018; 8 (1):17232.

Chicago/Turabian Style

Faisal Bin Ashraf; Ali Torabi Haghighi; Joakim Riml; Knut Alfredsen; Jarkko J. Koskela; Bjørn Kløve; Hannu Marttila. 2018. "Changes in short term river flow regulation and hydropeaking in Nordic rivers." Scientific Reports 8, no. 1: 17232.

Journal article
Published: 21 February 2018 in The Cryosphere
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In cold climate regions, the formation and break-up of river ice is important for river morphology, winter water supply, and riparian and instream ecology as well as for hydraulic engineering. Data on river ice is therefore significant, both to understand river ice processes directly and to assess ice effects on other systems. Ice measurement is complicated due to difficult site access, the inherent complexity of ice formations, and the potential danger involved in carrying out on-ice measurements. Remote sensing methods are therefore highly useful, and data from satellite-based sensors and, increasingly, aerial and terrestrial imagery are currently applied. Access to low cost drone systems with quality cameras and structure from motion software opens up a new possibility for mapping complex ice formations. Through this method, a georeferenced surface model can be built and data on ice thickness, spatial distribution, and volume can be extracted without accessing the ice, and with considerably fewer measurement efforts compared to traditional surveying methods. A methodology applied to ice mapping is outlined here, and examples are shown of how to successfully derive quantitative data on ice processes.

ACS Style

Knut Alfredsen; Christian Haas; Jeffrey A. Tuhtan; Peggy Zinke. Brief Communication: Mapping river ice using drones and structure from motion. The Cryosphere 2018, 12, 627 -633.

AMA Style

Knut Alfredsen, Christian Haas, Jeffrey A. Tuhtan, Peggy Zinke. Brief Communication: Mapping river ice using drones and structure from motion. The Cryosphere. 2018; 12 (2):627-633.

Chicago/Turabian Style

Knut Alfredsen; Christian Haas; Jeffrey A. Tuhtan; Peggy Zinke. 2018. "Brief Communication: Mapping river ice using drones and structure from motion." The Cryosphere 12, no. 2: 627-633.

Journal article
Published: 01 February 2018 in Journal of Hydrology
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Reliable runoff estimation is important for design of water infrastructure and flood risk management in urban catchments. We developed a spatially distributed Precipitation-Runoff (P-R) model that explicitly represents the land cover information, performs integrated modelling of surface and subsurface components of the urban precipitation water cycle and flow routing. We conducted parameter calibration and validation for a small (21.255ha) stormwater catchment in Trondheim City during Summer-Autumn events and season, and snow-influenced Winter-Spring seasons at high spatial and temporal resolutions of respectively 5mx5m grid size and 2 minutes. The calibration resulted in good performance measures (Nash-Sutcliffe efficiency, NSE = 0.65-0.94) and acceptable validation NSE for the seasonal and snow-influenced periods. The infiltration excess surface runoff dominates the peak flows while the contribution of subsurface flow to the sewer pipes also augments the peak flows. Based on the total volumes of simulated flow in sewer pipes (Qsim) and precipitation (P) during the calibration periods, the Qsim/P ranges from 21.44% for an event to 56.50% for the Winter-Spring season, which are in close agreement with the observed volumes (Qobs/P). The lowest percentage of precipitation volume that is transformed to the total simulated runoff in the catchment (QT) is 79.77%. Computation of evapotranspiration (ET) indicated that the ET/P is less than 3% for the events and snow-influenced seasons while it is about 18% for the Summer-Autumn season. The subsurface flow contribution to the sewer pipes are markedly higher than the total surface runoff volume for some events and the Summer-Autumn season. The peakiest flow rates correspond to the Winter-Spring season. Therefore, urban runoff simulation for design and management purposes should include two-way interactions between the subsurface runoff and flow in sewer pipes, and snow-influenced seasons. The developed urban P-R model is useful for better computation of runoff generated from different land cover, for assessments of stormwater management techniques (e.g. the Low Impact Development or LID) and the impacts of land cover and climate change. There are some simplifications or limitations such as the runoff routing does not involve detailed sewer hydraulics, effects of leakages from water supply systems and faulty/illegal connections from sanitary sewer are not considered, the model cannot identify actual locations of the interactions between the subsurface runoff and sewer pipes and lacks parsimony.

ACS Style

Teklu T. Hailegeorgis; Knut Alfredsen. High spatial–temporal resolution and integrated surface and subsurface precipitation-runoff modelling for a small stormwater catchment. Journal of Hydrology 2018, 557, 613 -630.

AMA Style

Teklu T. Hailegeorgis, Knut Alfredsen. High spatial–temporal resolution and integrated surface and subsurface precipitation-runoff modelling for a small stormwater catchment. Journal of Hydrology. 2018; 557 ():613-630.

Chicago/Turabian Style

Teklu T. Hailegeorgis; Knut Alfredsen. 2018. "High spatial–temporal resolution and integrated surface and subsurface precipitation-runoff modelling for a small stormwater catchment." Journal of Hydrology 557, no. : 613-630.

Journal article
Published: 01 December 2017 in Geomorphology
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ACS Style

Roser Casas-Mulet; Knut T. Alfredsen; Alexander H. McCluskey; Michael Stewardson. Key hydraulic drivers and patterns of fine sediment accumulation in gravel streambeds: A conceptual framework illustrated with a case study from the Kiewa River, Australia. Geomorphology 2017, 299, 152 -164.

AMA Style

Roser Casas-Mulet, Knut T. Alfredsen, Alexander H. McCluskey, Michael Stewardson. Key hydraulic drivers and patterns of fine sediment accumulation in gravel streambeds: A conceptual framework illustrated with a case study from the Kiewa River, Australia. Geomorphology. 2017; 299 ():152-164.

Chicago/Turabian Style

Roser Casas-Mulet; Knut T. Alfredsen; Alexander H. McCluskey; Michael Stewardson. 2017. "Key hydraulic drivers and patterns of fine sediment accumulation in gravel streambeds: A conceptual framework illustrated with a case study from the Kiewa River, Australia." Geomorphology 299, no. : 152-164.

Journal article
Published: 23 November 2017 in Water
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Preserving hydrological variability is important when developing environmental flow regimes, and a number of tools have been developed to support this process. A commonly applied method is the index of hydrological alteration (IHA), which describes a set of indices that can be used to assess changes in flow regimes. In cold climate regions, river ice can have large effects on flow regimes through frazil and anchor ice formation, ice cover formation, and ice break-up, and the impact of this is usually not included in the commonly used indexes. However, to understand the effect of ice formation and the break-up on the flow regime, the ice effects on the hydrology should be considered when assessing winter alteration indexes. This paper looks at the effects of river ice on winter flow conditions using data from Norwegian rivers, and discusses these effects in relation to hydrological variability. This paper also shows how indexes can be used to classify ice-induced variability, how this should be used to avoid ice-induced effects in the current analysis, and how this can be combined with the current indices to improve the winter flow regime classification. The findings from this paper show that frazil- and anchor-induced raises of the water level have a large impact on the perceived flow in winter, producing higher flow and deeper water than what the open water conditions discharge could do. Corresponding to this, winter lows connected to ice-induced high flows at other locations are also common. Finally, issues related to the assessment of the temporal and spatial effects of ice formation are discussed.

ACS Style

Knut Alfredsen. An Assessment of Ice Effects on Indices for Hydrological Alteration in Flow Regimes. Water 2017, 9, 914 .

AMA Style

Knut Alfredsen. An Assessment of Ice Effects on Indices for Hydrological Alteration in Flow Regimes. Water. 2017; 9 (12):914.

Chicago/Turabian Style

Knut Alfredsen. 2017. "An Assessment of Ice Effects on Indices for Hydrological Alteration in Flow Regimes." Water 9, no. 12: 914.

Journal article
Published: 01 February 2017 in Journal of Hydrology: Regional Studies
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Study region: 26 boreal catchments (mid-Norway). Study focus: We performed regional flood frequency analysis (RFFA) using the L-moments method and annual maximum series (AMS) of mean daily streamflow observations for reliable prediction of flood quantiles. We used similarity in at-site and regional parameters of distributions, high flow regime and seasonality, and runoff response from precipitation-runoff models to identify homogeneous catchments, bootstrap resampling for estimation of uncertainty and regression methods for prediction in ungauged basins (PUB). New hydrological insights for the region: The rigorous similarity criteria are useful for identification of catchments. Similarity in runoff response has the least identification power. For the PUB, a linear regression between index-flood and catchment area (R2 = 0.95) performed superior to a power-law (R2 = 0.80) and a linear regression between at-site quantiles and catchment area (e.g. R2 = 0.88 for a 200 year flood). There is considerable uncertainty in regional growth curves (e.g. −6.7% to −13.5% and +5.7% to +24.7% respectively for 95% lower and upper confidence limits (CL) for 2–1000 years return periods). The peaks of hourly AMS are 2–47% higher than that of the daily series. Quantile estimates from at-site flood frequency analysis (ASFFA) for some catchments are outside the 95% CL. Uncertainty estimation, sampling of flood events from instantaneous or high-resolution observations and comparative evaluation of RFFA with ASFFA are important

ACS Style

Teklu T. Hailegeorgis; Knut Alfredsen. Regional flood frequency analysis and prediction in ungauged basins including estimation of major uncertainties for mid-Norway. Journal of Hydrology: Regional Studies 2017, 9, 104 -126.

AMA Style

Teklu T. Hailegeorgis, Knut Alfredsen. Regional flood frequency analysis and prediction in ungauged basins including estimation of major uncertainties for mid-Norway. Journal of Hydrology: Regional Studies. 2017; 9 ():104-126.

Chicago/Turabian Style

Teklu T. Hailegeorgis; Knut Alfredsen. 2017. "Regional flood frequency analysis and prediction in ungauged basins including estimation of major uncertainties for mid-Norway." Journal of Hydrology: Regional Studies 9, no. : 104-126.

Journal article
Published: 01 January 2017 in Journal of Hydrology
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ACS Style

Teklu Hailegeorgis; Knut Alfredsen. Analyses of extreme precipitation and runoff events including uncertainties and reliability in design and management of urban water infrastructure. Journal of Hydrology 2017, 544, 290 -305.

AMA Style

Teklu Hailegeorgis, Knut Alfredsen. Analyses of extreme precipitation and runoff events including uncertainties and reliability in design and management of urban water infrastructure. Journal of Hydrology. 2017; 544 ():290-305.

Chicago/Turabian Style

Teklu Hailegeorgis; Knut Alfredsen. 2017. "Analyses of extreme precipitation and runoff events including uncertainties and reliability in design and management of urban water infrastructure." Journal of Hydrology 544, no. : 290-305.

Journal article
Published: 01 December 2016 in Science of The Total Environment
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ACS Style

Roser Casas-Mulet; Svein Jakob Saltveit; Knut Tore Alfredsen. Hydrological and thermal effects of hydropeaking on early life stages of salmonids: A modelling approach for implementing mitigation strategies. Science of The Total Environment 2016, 573, 1660 -1672.

AMA Style

Roser Casas-Mulet, Svein Jakob Saltveit, Knut Tore Alfredsen. Hydrological and thermal effects of hydropeaking on early life stages of salmonids: A modelling approach for implementing mitigation strategies. Science of The Total Environment. 2016; 573 ():1660-1672.

Chicago/Turabian Style

Roser Casas-Mulet; Svein Jakob Saltveit; Knut Tore Alfredsen. 2016. "Hydrological and thermal effects of hydropeaking on early life stages of salmonids: A modelling approach for implementing mitigation strategies." Science of The Total Environment 573, no. : 1660-1672.