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The Herting Project

This project is aiming for a ecosystem based management of the Ätran river to increase biodiversity, while still being able to use the river to produce energy from hydro power stations.

Ätran river from the sky.

Summary

The river Ätran in Southern Sweden has been subject to extensive efforts to improve water quality by liming operations since 1978, exceeding 100 000 metric tons of limestone, to counteract acidification caused by acid deposition. Massive economical efforts are made by authorities, industries and individuals to improve water quality and reduce nutrient impact. These efforts aims to restore ecosystems and populations of numerous migrating fish species in the river. The water shead is widely used for production of electricity and 35 hydro power stations are located in the water system. Only one of these sites, the Herting hydropower station, now provide a satisfactory solution for free fish migration.

The situation for migrating fish was not acceptable according to the ecological and sustainable strategies of the Municipality and caused considerable economical losses of tourist incomes for the Municipality and its operators and inhabitants. The Municipality of Falkenberg took action for Sourceto-Sea Management and engagement in collaborative projects, promote best practices, and to improve the management of land, water, coastal and marine linkages as expressed in the Manilla
Declaration adopted by 65 countries in 2012. This Action Platform facilitated contact between decision-makers and experts to provide on-demand knowledge, support, advice and guidance to policy making and implementation on freshwater, land, coast and sea. By doing so, we enhanced the efforts of the international community to fulfill its commitments to the Manila Declaration.

River connectivity is thereby one crucial factor concerning ecological functionality as most waters in Sweden partly suffers from heavily modified water bodies (HMWB) with thousands of dam constructions. The Municipality of Falkenberg consequently took part, together with seven European countries, in an Interreg IVB project named "Living North Sea" aiming to enhance "Free Fish Migration from Sea to Source".

The Municipality is the owner of two hydro power stations situated in a N2000 area close to the river mouth facing the Atlantic ocean. These stations were before 2013 a severe obstacle to upstream and downstream migration of genetically unique salmon (Salmo salar) and sea trout (Salmo trutta) populations in the river. Weak swimming fish species such as European eel (Anguilla anguilla), Sea lamprey (Pteromytzon maritimus), river lamprey (Pteromytzon fluviatilis), bullhead (Cottus gobio), lake (Lota lota) and cyprinide fishes were totally excluded from their important migration routes in the river totally drained by a massive hydropower dam built in 1944 and removed in 2013.

Main practical actions at the hydro power stations

  • Remove the hydro power dam.
  • Restore the pristine, original river bed.
  • Release a minimum of 11 kbm/s of water in the dried original river bed. 
  • Install a fish safe β-bar in front of the remaining hydro power station.
  • Install fish counters, video cameras and fish traps for monitoring of effects. All these practical actions were introduced in 2013.

The present report is mainly a summary of the project work and numerous positive effects generated during the work as a result of the measures taken to improve and restore the connectivity and ecosystem functions of the heavily modified river bed. The fish populations in Ätran and it´s important tributary Högvadsån has been constantly investigated since the 1950´s. The University of Karlstad had the mission to investigate the effects on fish populations some years before and after actions. Among other techniques they used telemetry and specially designed fish traps. The main conclusions concerning the Herting project are:

  • Best possible technique has been used.
  • The project is unique as both upstream and downstream fish migration has been solved properly.
  • Investigations are the most thorough ever in a project like this and is extremely well documented.
  • The results are the best and most positive ever recorded in similar projects, concearning both upstream and downstream migration of different fish species.

Conclusions concerning impact of fish populations

  • European eel and sea lamprey Upstream catches of alevines increased a hundred times at Ätrafors and five times in the tributary
    Lillån. Fish guidance efficiency (FGE) for silver eel increased from 0 % to 73 %. Passage efficiency (PE) for sea lamprey increased from 0 % to
    67 %.
  • Atlantic Salmon smolt and kelt FGE for smolt increased 400 % to
    85 %. Following actions PE for kelt measured 96 %.
  • Registered silver bright salmon in the Vaki counter/ Video camera increased after mitigation 2013 with 50 % or with 1500 to 2000 additional migrating salmon. This improvement is due to the Herting project
    combined with other positive actions.
  • Migration of Atlantic salmon starts one month earlier and spawning salmon reach the upper parts of spawning areas in Högvadsån one month earlier which is of grat importance ecologically and for an
    extended sport fishing period. Natural salmon migration is restored.
  • Estimated salmon fry production in the Herting rapids, the old pristine river bed restored as bypass, is 13 000 salmon fry. This considerably increase total salmon production and enhance sport fishing.

Swedish Agency for Marine and Water Management states about the project

New fish pass solutions at Herting hydro power station in River Ätran have radically improved migration for Atlantic Salmon, European eel and Sea lamprey. The innovative solutions with a big pristine fish pass and a
leaning β-bar illustrates the potential in replacement of old fish pass solutions with new designed solutions according to recommendations of Best Possible Technique (BPT). The Swedish Agency for Marine and Water Management states about the project: New fish pass solutions at Herting hydro power station in River Ätran have radically improved migration for Atlantic Salmon, European eel and Sea lamprey. The innovative solutions with a big pristine fish pass and a leaning β-bar illustrates the potential in replacement of old fish pass solutions with new designed solutions according to recommendations of Best Possible Technique (BPT). 

Natural fish migration and reproduction has radically improved in the Ätran river system following action within the Herting project 2013. These actions are crucial and beneficial in heavily modified water bodies (HMWB) to reach good ecological status, ecosystem resilience and salmon production in accordance with Swedish and international legislation.

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Published: 2017-11-02

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