Clearwater river (river type)

Like many clearwater rivers, the Xingu has sections with rapids that are home to many threatened rheophilic fish found nowhere else in the world[1]

A clearwater river is classified based on its chemistry, sediments and water colour. Clearwater rivers have a low conductivity, relatively low levels of dissolved solids, typically have a neutral to slightly acidic pH and are very clear with a greenish colour.[2][3][4] Clearwater rivers often have fast-flowing sections.[3]

The main clearwater rivers are South American and have their source in the Brazilian Plateau or the Guiana Shield.[4][5][6] Outside South America the classification is not commonly used, but rivers with clearwater characteristics are found elsewhere.[7]

Amazonian rivers fall into three main categories: clearwater, blackwater and whitewater. This classification system was first proposed by Alfred Russel Wallace in 1853 based on water colour, but the types were more clearly defined according to chemistry and physics by Harald Sioli [de] from the 1950s to the 1980s.[2][8][9] Although many Amazonian rivers fall clearly into one of these categories, others show a mix of characteristics and may vary depending on season and flood levels.[9][10]

  1. ^ Andrade, M.C.; L.M. Sousa; R.P. Ota; M. Jégu; T. Giarrizzo (2016). "Redescription and Geographical Distribution of the Endangered Fish Ossubtus xinguense Jégu 1992 (Characiformes, Serrasalmidae) with Comments on Conservation of the Rheophilic Fauna of the Xingu River". PLOS ONE. 11 (9): e0161398. Bibcode:2016PLoSO..1161398A. doi:10.1371/journal.pone.0161398. PMC 5035070. PMID 27662358.
  2. ^ a b Duncan, W.P.; M.N. Fernandes (2010). "Physicochemical characterization of the white, black, and clearwater rivers of the Amazon Basin and its implications on the distribution of freshwater stingrays (Chondrichthyes, Potamotrygonidae)". PanamJAS. 5 (3): 454–464.
  3. ^ a b Giovanetti, T.A.; Vriends, M.M. (1991). Discus Fish. Barron's Educational Serie. p. 15. ISBN 0-8120-4669-2.
  4. ^ a b van der Sleen, P.; J.S. Albert, eds. (2017). Field Guide to the Fishes of the Amazon, Orinoco, and Guianas. Princeton University Press. pp. 13–18. ISBN 978-0-691-17074-9.
  5. ^ Junk, W.J.; Piedade, M.T.F.; Schöngart, J.; Cohn-Haft, M.; Adeney, J.M.; Wittmann, F.A. (2011). "Classification of Major Naturally-Occurring Amazonian Lowland Wetlands". Wetlands. 31 (4): 623–640. doi:10.1007/s13157-011-0190-7. S2CID 36001397.
  6. ^ Venticinque; Forsberg; Barthem; Petry; Hess; Mercado; Cañas; Montoya; Durigan; Goulding (2016). "An explicit GIS-based river basin framework for aquatic ecosystem conservation in the Amazon". Earth Syst. Sci. Data. 8 (2): 651–661. Bibcode:2016ESSD....8..651V. doi:10.5194/essd-8-651-2016.
  7. ^ Winemiller, K.O.; A.A. Agostinho; É.P. Caramaschi (2008). "Fish Ecology in Tropical Streams". In Dudgeon, D. (ed.). Tropical Stream Ecology. Academic Press. pp. 112–113. ISBN 978-0-12-088449-0.
  8. ^ Sioli, H., ed. (1984). The Amazon: Limnology and landscape ecology of a mighty tropical river and its basin. Springer. pp. 160–161, 219, 276–280, 445, 493–494. ISBN 978-94-009-6544-7.
  9. ^ a b Ríos-Villamizar, E.A.; M.T.F. Piedade; J.G. da Costa; J.M. Adeney; J. Junk (2013). "Chemistry of different Amazonian water types for river classification: A preliminary review".
  10. ^ Goulding, M.; M.L. Carvalho (1982). "Life history and management of the tambaqui (Colossoma macropomum, Characidae): an important Amazonian food fish". Revista Brasileira de Zoologia. 1 (2): 107–133. doi:10.1590/S0101-81751982000200001.