Trends in number of global freeflowing rivers greater than 1,000km in length Trends from pre-1900 to the present day and estimated to 2020 (line), in comparison with the number of rivers dammed over time (bars). worldwildlife.org

Trends in number of global freeflowing rivers greater than 1,000km in length Trends from pre-1900 to the present day and estimated to 2020 (line), in comparison with the number of rivers dammed over time (bars). WWF, 2006

The rapid development of water management infrastructure – such as dams, dykes, levees, and diversion channels – have left very few rivers entirely free flowing. Of the approximately 177 rivers greater than 1,000km in length, only around a third remain free flowing and without dams on their main channel (WWF, 2006a).

While clearly this infrastructure provides benefits at one level, such as hydropower or irrigation, there is often a hidden cost to aquatic ecosystems and the wider ecosystem services that they provide. In order to sustain the wealth of natural processes provided by freshwater ecosystems – such as sediment transport and nutrient delivery, which are vital to farmers in floodplains and deltas; migratory connectivity, vital to inland fisheries; and flood storage, vital to downstream cities – it is imperative to appreciate the importance of free flowing rivers, and developing infrastructure with a basin-wide vision.

2012 Living Planet Report [pdf]

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