This week the BBC featured an article describing the largest-scale project of dam removal to date on the Klamath River in the Western USA. The project involves the gradual disassembling of four out of eight hydroelectric dams. These dams were built during the dam-boom in the America that lasted from the late 19th to the mid 20th century. Removal is now planned at a cost of $450m as a result of campaigning from environmental groups and the Yurok native American tribe, whose livelihoods were severely damaged by the dams’ effects on fishing.
Last year, 90 dams were removed in America, putting the total figure of dam deconstruction in America at 1,700 according to America Rivers. This drive for dam reduction stems from pressure to restore habitats and livelihoods, but also because of legislative changes that are forcing dam-owners to mitigate the infrastructure’s impact. Often installing fish ladders or changing hydroelectric production are simply too costly to justify re-licensing dams.
This latest case of dam removal reminds us that dams’ impacts are not only on displacement and the creation of a reservoir. Downstream of the dam wall, river flow is greatly modified. A reduced baseline flow tends to form a shallower, sometimes warmer habitat where deposition of fine sediment increases. This influences the ability of animal species, especially fish, to survive, feed and reproduce. Hydropower dams tend to create a harsher environment of extremes flows, as water is released to meet energy demands that plants and animals find harder to adapt to. This undermines riparian zones and makes them less habitable to species of plants and also animals such as mammals and birds.
The dam itself also forms a barrier on the river landscape which, unless carefully planned, impedes the travel of migratory species in either upstream or downstream direction, affecting breeding potential and survival. The most iconic example of this is for salmonids fish, which breed in river headwaters but spend their adult life at sea, thus requiring free movement along the river continuum.
The growing trend of dam dismantling in America therefore reminds us that when negative impacts are fully measured, dams may not be worth building.
However, this trend lies in stark contrast to the ongoing resurgence of dam building seen across the ‘Global South’. Fuelled by the internationalisation of finance and dam-builders from China, India, Brazil and Turkey dam building increased from the mid-2000s. The return to dam-financing by the World Bank, alongside growing global interest in renewable energy, has spurred this resurgence further. Whilst academics have demonstrated important changes in the way dams are built, the rising number of dam removals in the USA reminds us of the infrastructure’s potential long-term impacts over a river’s geography. Thus, the World Commission on Dams’ 2000 message to always assess dams alongside other development alternatives continues to ring true.
If dams are deemed necessary, holistic assessment of their long-term and short-term impacts will be necessary. Analysis should not only consider the impact of a reservoir, but also the downstream effects on rivers and particularly on the operation of dams.
Note: This article gives the views of the author/academic featured and does not represent the views of FutureDAMS as a whole.