Hydropower Development – Ecological Effects

Abstract

Hydropower development has taken place in salmon rivers in different countries since the 1880s, and peaked during the 1950s and 1960s. In some countries there have been serious negative effects for Atlantic salmon populations, but in others the effects have been negligible. The negative effects on single populations vary greatly, ranging from complete extinction to small negative effects; there have even been a few cases where populations have actually benefi ted from the regulation. One major concern is that large dams may impair the upstream migration of Atlantic salmon and also affect the downstream migration of smolts and kelts through hydropower turbines and reservoirs. River regulations often change the hydrological scheme in rivers, thus affecting water discharge, water temperature and water quality, all of which are parameters that may affect the survival of salmon both directly and indirectly.Traditional mitigatory measures in regulated rivers are fi sh stocking, weirs, fi sh ladders, downstream fi sh -passage facilities, and different kinds of habitat adjustments.Minimum water fl ow has been one of the oldest mitigatory actions, and there is documentation of a positive correlation between winter discharge and the survival of juvenile salmon in winter. An inproved understanding for a broader use of water for environmental purposes has in some cases resulted in new manoeuvring rules for power plants that should improve the environment for the salmon population.It is imperative for future research to identify the bottlenecks that may cause high mortality, and a major task for the future management will be to maintain river -specifi c populations at levels that ensure natural reproduction and recruitment. Different types of hydropower facilities, depending on the landscape and the amount and distribution of water, have been developed in Atlantic salmon rivers. This development has resulted in serious negative effects for Atlantic salmon populations in some countries and rivers, while the effects have been negligible in other countries and/or rivers. As a backdrop, we present briefl y the history of hydropower development in countries where the effects on Atlantic salmon have been substantial. NorwayThe fi rst hydropower station in Europe was built in Norway in 1882 and this event initiated a period of construction of hydropower development for local use. Between 1945 and 1961, more than 200 new power stations were built (Hveding 1992 ). The period from 1961 to 1980 witnessed the completion of many large hydropower projects. Storage is the most common type of hydropower development in Norway. The impacts of this kind of hydropower development are very complex and depend on the running of power stations, the release strategy of water from reservoirs and the water quality in the different parts of the watercourse.In Norway there are 452 rivers which have or have had a self -reproducing population of Atlantic salmon. In 84 (19%) of these rivers, hydropower development is a signifi cant factor infl uencing the s...

Can the river location within a fjord explain the density of Atlantic salmon and sea trout?

“…This is in contrast to studies that have shown that salmonids can be strongly affected by these factors (Aas et al 2010;Johnson et al 2011;Jonsson & Jonsson 2011). This discrepancy could either reflect the true situation for our sites and years, or be explained by a suboptimal model design.…”

Linking individual behaviour and migration success inSalmo salarsmolts approaching a water withdrawal site: implications for management

“…Dam building in rivers and streams has occurred globally for decades (Roscoe and Hinch 2010;Johnsen et al 2011). In potamodromous and diadromous fishes, dams and weirs often delay or inhibit access to spawning (Gehrke et al 2002;Gosset et al 2006), nursery (Saunders 1960;Arnekleiv and Rønning 2004) and foraging (Agostinho et al 2002;Aarestrup and Koed 2003) areas.…”

The major threats to Atlantic salmon in Norway

“…The effects on Atlantic salmon vary substantially among rivers (Johnsen et al, 2011;Birkel et al, 2014). This impact factor ranked high along the effect axis because it affects nearly 20% of the populations, and 19 populations may have been lost due to hydropower development (Johnsen et al, 2011).…”

“…This impact factor ranked high along the effect axis because it affects nearly 20% of the populations, and 19 populations may have been lost due to hydropower development (Johnsen et al, 2011). The effect in terms of reduced adult returns was classified as being between moderate and strong, based on published studies from Norway and elsewhere (Murchie et al, 2008;Ugedal et al, 2008;Johnsen et al, 2010Johnsen et al, , 2011Otero et al, 2011;Birkel et al, 2014;Hvidsten et al, 2015;Stich et al, 2015;Bilotta et al, 2016). Hydropower developments in Norway started in 1882, peaked during 1945-1961, and many of the extensive regulations were completed by 1980 (Johnsen et al, 2011).…”