Many freshwater fish species around the world need to migrate for their survival. During their journey they often encounter man-made barriers, such as dams and weirs, which impede their migrations upstream or downstream of barriers. A well known solution to this problem, is the construction of a fishway that allows fish to pass a physical obstacle. From as early as the 18th century, fishways have been implemented. Over the decennia since then, knowledge, technology and experience have developed substantially, resulting in many different fishway designs specific for different regions or fish species. This can vary from a nature-like fishway to a lock fishway (see above figure, taken out of the From Sea to Source 2.0 book). In the From Sea to Source 2.0 book there are various examples of fishways and fishway designs.
Along with the many new insights into fishway effectiveness and efficiency, there is more evidence to suggest that fishways are not the ultimate solution to fish passage. In some cases the presence of a fishway has been shown to impact fish populations, as was shown by Pompeu and his colleagues in Brazil (Pompeu et al., 2011). In other cases, the post-construction management and maintenance is often neglected, particularly in developing countries, which not only leads to severe gaps in important information about the performance of fishways, but also hampers the advantages that the fishways provide.
From more information, see the From Sea to Source 2.0 book or the various best practice guidelines from your region. In Europe, the DWA, 2014 guideline (Fischaufstiegsanlagen und fischpassierbare, Bauwerke – Gestaltung, Bemessung, Qualitätssicherung. Merkblatt DWA-M 509, D-Hennef.) and the CEN/TC 230, 2018 guideline (Guidance for assessing the efficiency and related metrics of fish passage solutions using telemetry, version 2.81), both offer comprehensive overviews of fishways.
Fishways drawings (c) From Sea to Source 2.0; Maintenance cartoon (c)Auke Herrema
There are thousands of solutions to restore rivers and their ecosystems around the world. According to many experts, one of the best solutions is to simply remove barriers from the rivers. That basically means taking out a weir, a dam or a blockage from the river.
The major advantage of this, is that the river can flow unhindered and go back to functioning naturally. You may be asking yourself: “why would this be important?”
The answer is that ultimately a naturally flowing, healthy and balanced river can help ensure that there:
is enough water for all water uses along the river,
are fewer extreme conditions caused by droughts and flooding,
are fewer impacts from climate change,
are more resources in the river for people to use,
are better flow levels and water quality in the river,
are better habitats for animals in the ecosystem,
is a higher biodiversity of animals (birds, fish, bugs, frogs, crocodiles and more) for future generations,
are enough healthy populations of fish for people to catch and to eat, etc.
There are thousands of dams that have been built over the years, however, many of them now do not have a purpose, have become a safety hazard and/or are an economic drain. In the From Sea to Source 2.0 book the incentives for dam removals are further detailed.
Here are two examples of how a dam removal has improved the economy of an area:
17 dams were removed in the Conestoga River in USA resulted in rejuvenated fisheries that were expected to generate approximately $2-3 million in revenue for local economies
In Sweden, a dam removal quadrupled the fish stocks in the region and increased the value of a fishing day for local fishermen.
Of course the removal of a dam can be a really expensive endeavor, but it also doesn’t have to be. For example removing a small dam can cost as little as $2,000.
Do you want to know more?
There are currently many sources of information online, ranging from smaller watershed groups to large organisations. Here are some examples of the sources of updated information about dam removals currently available online:
American Rivers: A non-profit organization in USA that collects data annually on dam removals.
Dam Removal Europe:A collaborative project of 5 organisations with over 20 supporters, which intends to create a movement in Europe around a common ambition to have healthy free-flowing rivers full of fishes by removing barriers.
From Sea to Source 2.0: In the downloadable book there are several dam removal case studies, details of dam removals from around the world and a flow chart summarising the four basic steps within the dam removal process.