The geochemistry of the Paraná River: An overview

DEPETRIS, P.J., PASQUINI, A. I

The Middle Paraná River: Limnology of a Subtropical Wetland

SPRINGER

Año: 2007; p. 143 - 174

The geochemistry of the Paraná dissolved and suspended load is controlled, as in all other world rivers, by many interrelated natural and anthropogenic factors. Among such set of complex interactions, there are a few that are here considered worthy of special consideration: a) the occurrence of ENSO-triggered significant flooding with 2-5 year periodicity and the conclusive evidence that its mean discharge has been increasing since the mid-1970s, mostly due to the flow increase observed during low discharge months (i.e., southern winter) ; b) the prevailing sedimentary nature and tectonically-active headwaters of the Bermejo and Pilcomayo rivers that determines very high erosion rates that supply most of the ~100 million tons load of essentially recycled sediments (i.e., material that has passed more than once through the exogenous cycle) that annually reach the Paraná middle stretch; and c) the existence of wetlands in the headwaters (i.e., the Gran Pantanal) and an extensive flood plain in the middle stretch, with luxuriant riparian vegetation and a myriad of ponds and streams, which mostly functions as a carbon source, and exerts a significant control on the riverine biogeochemistry. In as much as all these factors are substantially affected by the ongoing climatic change, a discernible modification in the Paraná?s main geochemical characteristics must be expected to occur in the foreseeable future.