The experimental flume “Kungsrännan” under construction in Älvkarleby.

Hydropower dams block migration routes and disrupt longitudinal connectivity in rivers, thereby posing a threat to migratory fish species. Various fish passage solutions have been implemented to improve connectivity with varying success. For downstream migrating fish, low sloping turbine intake racks are used to guide fish to bypasses. Current knowledge, however, is based on hydropower plants with intake capacities <72 cm. There is also a trade-off between electricity generation and fish guidance (smaller bar spacing – better for fish, larger bar spacing – better for hydropower). Currently, gap widths/bar spacings of 10-20 mm are recommended but behavioral guidance effects open up the possibility of larger bar spacings.

During spring, Karlstad University in collaboration with Vattenfall and NINA, will experimentally study the behavior and passage performance of downstream migrating salmon smolts approaching a variety of low sloping intake racks. The experiments will be conducted in a new large experimental flume – Kungsrännan – at the Vattenfall hydraulic laboratory in Älvkarleby, Sweden. We will study the passage behavior and performance of smolts for alpha racks – inclined from the bottom up – and beta racks – angled from one side of the channel to the other – with different gap-widths (15-30 mm).

For this, we are looking for one interested and ambitious assistant to join us in Älvkarleby. The assistant will be salaried and is needed from mid-April to mid-June. Housing in the area can be provided. Are you interested in joining us? Contact Olle Calles for more information.

The principle behind downstream fish passage solutions using low sloping intake racks. The fish is swept and guided along a beta rack to a bypass at the rack’s downstream end.

Marius Heiß, a master student who has been working by River Ätran has finished his thesis titled “Evaluation of innovative rehabilitation measures targeting downstream migrating Atlantic salmon smolt (Salmo salar) at a hydroelectric power plant in southern Sweden” . In the abstract he writes:

“The ecological state of streams and rivers has aggravated on a global scale due to a wide range of anthropogenic influences. The disruption of migratory routes for diadromous fishes by hydroelectric power plants have led to major stock declines over the last century. As a result fishways have been built at many hydroelectric power plants in Europe to improve migration conditions at such obstacles. This measure may improve upstream migration, but typically does not solve corresponding passage problems for downstream migrating fish. Consequently large numbers of downstream migrants, e.g. Atlantic salmon smolt (Salmo salar), are forced to pass turbines on their way to the ocean. There are few rehabilitation measures specifically targeting downstream passage conditions and most of them lack scientific evaluation.

This thesis reports on a radio-telemetric-study to evaluate innovative rehabilitation measures targeting downstream migrating Atlantic salmon smolt, at a hydropower plant in southern Sweden. There had been extensive renovation works at the study site to improve passage conditions for migrating fishes. The conventional turbine rack and a modified conventional trash gate were replaced by a low sloping β-rack adjacent to a full depth bypass channel. Moreover, a nature-like fishway was built at the site.
The results show that the evaluated rehabilitation measures were able to significantly improve downstream passage conditions for Atlantic salmon smolts. Total passage success was high (94%) and bypass efficiency has increased by 68%, whereas the number of smolts passing through the turbines was reduced by 63%. Although there were some issues associated with the monitoring station in the new bypass, the results are promising and so prospective constructions of low-sloping β-racks with full-depth bypasses should lead to improved downstream passage conditions at additional hydroelectric power plants.”

Read the master thesis here.

På tisdag, den 17:e september, klockan 13:15 inleds höstens seminarie-serie på Biologiavdelningen vid Karlstads Universitet. Det är vår egen John Piccolo som ska prata om smoltvandring i Klarälven. Alla är välkomna! Rum 5F416 är det som gäller.