The global navigable waterways encompass a network of 700,000 km that connects river basins across geographic regions. In the European Union, more than 50,000 km navigable rivers and canals create a dense web of waterways. Today, you may travel from southern France to western Siberia without entering the sea. Waterways facilitate the spreading of exotic and invasive organisms, which may lead to a homogenisation of freshwater biodiversity. Plans exist to upgrade and enlarge existing waterways, such as the Danube-Main-Rhine Waterway, and to create new waterways. At the same time, most of the planned interbasin transfer projects (Table 4.2) will support inland navigation too.
In South America, the 3,440 km Parana-Paraguay waterway, called Hidrovia, will connect Cáceres (Brazil) with Nueva Palmira (Uruguay). The main aim is to facilitate the export of soybeans, minerals, timber and other commodities from the interior. Extensive wetlands, in particular the Pantanal, will be affected by this project (Huszar et al. 1999; Gottgens et al. 2001). About 7.3 × 106 m3 of sediment are dredged to enforce and straighten the rivers for navigation and to build ports. The calculated investment costs for a total of 88 individual projects are estimated at USD 4 billion (iirsa.org).
Hydropower Mega Dams
Currently, at least 161 very large hydropower dams, with a capacity of more than 1,000 MW each, are globally either under construction or planned. For illustration, a dam of 1,000 MW could, if to 100 % efﬁciently working, provide the annual electric consumption for 1.2 million people, assuming the electric consumption per capita in Germany in 2011 (World Bank 2014). This corresponds to sufﬁcient energy to fully power a city almost as large and wealthy as Munich (2011: 1.38 million). The total capacity of the future mega dams amounts to 440 GW; most of the dams are planned in developing countries and emerging economies (Fig. 4.1), where consumption rates per capita are much lower than in Germany.
Not surprisingly, the global distribution of these future dams is not equal (Fig. 4.1). The largest number of large dams will be constructed in the Asian countries of China, Pakistan and Myanmar, in the South American countries of Brazil and Peru as well as the African countries of the Democratic Republic of Congo, Ethiopia and Nigeria.
What does this mean for the ecology? The Yangtze basin will be fragmented by
the highest number of hydropower dams in Asia (33 % of the continental total). In South America, the Amazon basin will receive 61 % of the future hydropower dams of the continent providing 69 % of the planned capacity. And in Africa, mainly the Zambesi basin will be confronted with new dams (35 % of continental total) while the Grand Inga hydropower dam alone and planned in the Congo basin will provide 55 % of the capacity planned in Africa. The Yangtze and the Zambesi basins have already been classiﬁed as heavily fragmented, whereas the Amazon and the Congo
Fig. 4.1 Global distribution of future hydropower dams >1,000 MW that are under construction or planned, status 2014 (Data: Zarﬂ et al. (2015))
basins are among the moderately fragmented river systems (Nilsson et al. 2005). This means that these additional huge hydropower dams might change the fragmentation degree. There are also basins that have been classiﬁed as not fragmented so far that will face an increase in fragmentation, e.g. the Salween basin in Asia with 11 hydropower dams planned. Fragmentation leads to habitat destruction and prevents migration of aquatic organisms which might result in a decrease of biodiversity. In addition, hydropower dam operation will change discharge patterns, transport of sediments and water temperature.
For some of the “smaller” very large dams (1,000–2,000 MW) data on the size of the planned reservoir is known, which ranges up to 1,230 km2 for the Mupata George in the Zambesi basin. This exceeds the size of Lake Yssel in the Netherlands and just indicates the area that might be required for huge hydropower dam constructions. One of the largest reservoirs by surface area, Lake Volta in Ghana, is ﬂooding more than 8,500 km2. This does not only affect the environment like ﬂooding of terrestrial habitats, but also has social impacts due to the required relocation of the residential human population.