Ecological connectivity for fish in regulated rivers


While solutions for upstream migration of salmonid fishes are well developed, downstream migration and measures to prevent fatal turbine passage remains a major challenge for most species. This project will find and test various methods for guiding fish away from the turbines.

Small bar-spacing racks that prevents fish from entering the turbine area represent “best practice” solutions and should be used in new facilities. However, the design of several existing large hydropower facilities in Norway and cost-benefit trade-offs for rack solutions point towards the need for alternative solutions.

The SafePass project (NRC: 2015 - April 2019) address the topic of downstream migration along two major lines of research: First, by providing basic knowledge on the migration behavior and links to hydraulic conditions of target species in front of HP intakes to provide design criteria for guiding measures, away from the intake and into bypass structures. Second, by developing small bar-spacing rack solutions applicable for HP facilities in Norway.

We have performed detailed studies of hydraulic properties (including head losses) of different rack designs with small bar-spacing (15 mm), and during 2018 SafePass will explore the guiding efficiency (salmon smolts and eel) of the most promising designs, also when bar spacing are increased somewhat (25 mm).

A major challenge with small bar-spacing racks are rack cleaning. While some systems have been developed internationally, the technology cannot be directly transferred to many Norwegian facilities, due to the size and design of the intake structures (often a tunnel, in contrast to intake channels in many European facilities).

Based on the interdisciplinary competence profile of HydroCen, we aim at developing and testing innovative rack cleaning systems applicable to Norwegian HP intake structures and small bar-spacing racks (including horizontal bar designs).

Unique data

The SafePass project has provided detailed migration tracks of salmon smolts (rivers Mandalselva and Orkla), salmon kelts (river Orkla), brown trout smolts and kelts (river Gudbrandsdalslågen) and silver eel (river Ätran, Sweeden).

These datasets are of unique quality and combined with hydraulic modelling the aim is to develop migrations model that can predict migration route and allow model based evaluation of the effects of different guiding measures. The analyses of these extensive datasets have proven to be time- and resource demanding, and project 4.2 will provide additional resources to fully exploit the potential of the data collected.

Guiding fish away from the intake

The major limitation for SafePass in terms of data analyses has been economy, because of the high allocation to the field studies.

However, the field studies in River Mandalselva and Orkla has already shown that the risk of turbine passage depend on the entry position of the fish to the intake area, relative to the intake position. Fish entering the area on the opposite bank to the intake had much higher probability of bypass migration. Moreover, a simple 1 m deep louvre in front of the HP intake in Mandalselva significantly reduced the risk of turbine passage.

These observations support an assumption that floating devises (louvres) may guide fish away from turbine areas.

There are limited knowledge available on the design and guiding efficiency of louvres and in this project we aim to develop and test innovative louvre designs, both in terms of guiding efficiencies, material, hydraulic and operational properties. Preferred and avoided hydraulic properties (velocities, turbulence, eddies) identified in the field and laboratory studies will be used as starting points for the designs.

Publications 2019

Conference Proceedings 2019

Forseth, Torbjørn. Overview of SafePass & HydroCen - Solutions for downstream migration of fish past hydropower installations. Workshop SafePass, HydroCen & FitHydro; 2019-03-18 - 2019-03-19

Publications 2018

Hedger, Richard David; Sauterleute, Julian Friedrich; Sundt-Hansen, Line Elisabeth Breivik; Forseth, Torbjørn; Ugedal, Ola; Diserud, Ola Håvard; Bakken, Tor Haakon. Modeling the effect of hydropeaking‐induced stranding mortality on Atlantic salmon population abundanceEcohydrology 11(5):e1960 · March 2018

Fjeldstad, Hans-Petter; Pulg, Ulrich; Forseth, Torbjørn. Safe two-way migration for salmonids and eel past hydropower structures in Europe: a review and recommendations for best-practice solutionsMarine and Freshwater Research. 2018, 69 1834-1847.

Thomas Schleker a, Hans-Petter Fjeldstad b, Hydropower and fish – Report and messages from workshop on research and innovation in the context of the European policy framework. Science of The Total Environment. Volume 647, 10 January 2019, Pages 1368-1372

Silva, Ana T.; Midwood, Jonathan D.; Aarestrup, Kim; Pottinger, Tom G.; Madsen, Steffen S.; Cooke, Steven J..  The Influence of Sex, Parasitism, and Ontogeny on the Physiological Response of European Eels (Anguilla anguilla) to an Abiotic Stressor. Physiological and Biochemical Zoology 2018 ; Volum 91.(4) s. 976-986.

Szabo-Meszaros, M., Navaratnam, C.U., Aberle, J., Silva, T.A., Forseth, T., Calles, O., Fjeldstad, H-P. & Alfredsen, KExperimental hydraulics on fish-friendly trash-racks: an ecological approach. Ecological Engineering

Conference Proceedings 2018

Hedger R. D., Sauterleute J., Sundt-Hansen L.E, Forseth T., Ugedal, O., Diserud O., Bakken T. H.  Dynamically modelling the sensitivity of an Atlantic salmon population to hydropeaking-induced stranding mortality. EcoHydrology

Fjeldstad, H-P., Pulg, U. & Forseth, T. Sikker toveis fiskevandring forbi vannkraftverk. Kunnskapsoppsummering og mønsterpraksis. SINTEF Energi AS

Forseth, Torbjørn. HydroCen og miljødesign Nea. Åpent folkemøte; 2018-10-24 - 2018-10-24. NINA

Forseth, Torbjørn. Nye løsninger for fiskevandringer forbi kraftverk. Teknologidagen Hydro Energi; 2018-11-22 - 2018-11-22. NINA 

Forseth, Torbjørn. SafePass - et kvantesprang for kunnskap om vandringsløsninger i Norge. Kraftverkshydrologi og miljøforhold; 2018-11-20 - 2018-11-21. NINA 

Helland, Ingeborg Palm. Fremtidens energisystem – på lag med naturen?. Energiforskningskonferansen; 2018-05-30. NINA 

Helland, Ingeborg Palm; Eloranta, Antti; Power, Michael. Towards an environmental design of hydropower operations in reservoirs. ASLO Summer meeting 2018; 2018-06-10 - 2018-06-15. NINA


Ana da Silva

Research scientist
Project leader


Phone: 455 03 711

Torbjørn Forseth

Senior Research Scientist


Phone: +47 926 43 437

About the project

Full project title: Ecological connectivity for fish in regulated rivers

Duration: 2018-2020

Objective: The primary objective will be obtained by a joint effort on analyses of experimental data from SafePass and through new laboratory and field experiments.

Researchers working on the project: Ana da Silva, Torbjørn Forseth, Karl Øystein Gjelland, Richard Hedger, Knut Alfredsen, Leif Lia, Ole Gunnar Dalhaug, Hans-Petter Fjeldstad, Ulrich Pulg, Sebastian Strazl, Lennart Schöenfelder, Marcell Szabo-Meszaros.

R&D Partners: NINA, SINTEF Energi, NTNU and UNI Research

Associated projects: SafePass (CEDREN)

Ph.D. working on the project: Halvor Kjærås