Fluvial Sediments. Main Channel and Alluvial Plain Interrelationships

AMSLER, M.; EDMUNDO DRAGO,; PAIRA, A.R.

The Middle Paraná River: Limnology of a Subtropical Wetland

Springer-Verlag

Lugar: Berlín; Año: 2007; p. 83 - 122

The quantity and quality of sediments supplied to such a large and complexsystem as the middle Paraná River, its differential transport through thedrainage network, and the eventual sedimentation rates on the adjacent alluvial plain, are all variables that need to be known due to their crucial role onthe type and survival of communities characterizing certain environmentsand on the possible interrelationships among them. Since the water transparency, the transfer of some nutrients and salts, the periodical renovation ofalluvial plain surface soils, and the substratum features of lotic and lenticenvironments are all factors (processes) closely related to sediment, its pondering as a key variable for the state regulation of complex fluvial ecosystems has a sound justification.This chapter will address the topic of sediment. The amount of the totalsediment transport in the main channel and the principal secondary streamsof the alluvial plain is focused distinguishing between the two fractions composing the solid discharge: the bed sediment (fine and medium sands in thiscase), and the finer sizes, silts and clays. These small particles predominate in the sediment transported through the system. They are essentially suppliedby the Bermejo River from the Andean range, on the west side of the ParanáRiver basin. The silts and clays transport is considered with certain detail dueto its quantity as well as the reductions verified in the amounts supplied bythe upper Paraná River owing to anthropogenic factors occurred in theBrazilian areas of the basin. Those reductions reflected on the periodicalsedimentation along the alluvial valley of the middle reach at severalhydrological circumstances. This fact is stressed within the chapter conclusions together with the necessity of preserving the Bermejo River sedimentsupply, in order to assure the large wetland that involves the middle ParanáRiver reach.