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Since 2005, the last Sunday of September has been celebrated annually as World Rivers Day. This global celebration of the rivers around the world is aimed at highlighting the value of rivers and the importance of sustaining river health. Global activities include riverside cleanups, school projects, art exhibitions, music festivals and more.

World Rivers Day originated in Canada, where a very successful BC Rivers Day, held in British Columbia since 1980, led to the creation of Canadian Rivers Day. This eventually gave rise to World Rivers Day, launched in 2005 as part of the United Nations’ Water for Life Decade initiative.

The Fish River Canyon, Namibia. Rivers are the arteries of the earth – keeping them clean, unblocked and free-flowing is critical for the health of the planet.
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According to the World Rivers Day website, the two key global issues requiring attention are the decline of river fish populations and the construction of dams.

The construction of large dams in rivers can have severe environmental, economic and human impacts.

Environmentally, one of the biggest issues relate to the impact of dams on fish populations – dam walls block fish migrations and in some cases completely separate the fish’s spawning habitats from their rearing habitats, which can have disasterous effects on river fish populations. The dam walls also trap sediments, affecting physical processes and habitats downstream. The establishment of a dam also changes the upstream part of the river from a free-flowing ecosystem to a stationary reservoir habitat, affecting it chemically and physically, threatening existing fauna and flora and introducing new, invasive species. To quote the International Rivers Organisation, “Large dams have led to the extinction of many fish and other aquatic species, the disappearance of birds in floodplains, huge losses of forest, wetland and farmland, erosion of coastal deltas, and many other unmitigable impacts.”

Large dams are an important source of hydropower and drinking water, but they can have negative economic impacts as well. Aside from the huge cost of building and maintaining these dams, excessive dependence on hydropower can be a risky strategy in a world where climate change can severely affect rainfall patterns, potentially leading to drought induced power blackouts. While hydropower is an important sustainable power source, and an important part of an energy-secure future, it should be included as one component in a diversified power supply regime (including wind, solar etc) to mitigate economic risk.

Finally, there is the human impact, with the World Commission on Dams estimating that the development of large dams have forced between 40 and 80 million people from their land in the past half century. This has particularly impacted the poorer countries of the world, where most of the world’s large dams are being constructed. Beyond those directly displaced by the dam reservoir, large dams affect millions of people living downstream and upstream from the dam, as availability of clean water, food sources and other natural resources have been affected. Changed ecosystems, particularly in the tropics, have also resulted in the introduction of diseases like urinary and intestinal schistosomiasis (bilharzia).

The Gariep Dam, South Africa. Dams are critical sources of energy and continuous water supply, but can also severely affect river-related ecosystems.
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Considering the importance of dams in energy creation, provision of drinking water etc, a balance obviously has to be struck between the advantages and disadvantages of building dams. Perhaps the key message lies in the following recommendation from the World Commission on Dams:

“Rivers, watersheds and aquatic ecosystems are the biological engines of the planet. They are the basis for life and the livelihoods of local communities. Dams transform landscapes and create risks of irreversible impacts. Understanding, protecting and restoring ecosystems at river basin level is essential to foster equitable human development and the welfare of all species.

Options assessment and decision-making around river development prioritises the avoidance of impacts, followed by the minimisation and mitigation of harm to the health and integrity of the river system. Avoiding impacts through good site selection and project design is a priority. Releasing tailor-made environmental flows can help maintain downstream ecosystems and the communities that depend on them.”