The parana river under extreme flooding: a hydrological and hydro-geochemical insight
All fluvial systems may be subjected to extreme floods that impact deeply on their hydrological and bio-geochemical dynamics. Large rivers (i.e., continental-size drainage basins) are exposed to such drastic alterations, which in some cases have appeared as more frequent or severe in the recent past, probably as a consequence of the ongoing world-wide climatic change. The Parana River, one of the worlds largest fluvial systems, exhibits an active tele-connection between extreme flooding and the occurrence of ENSO events in the Pacific. Furthermore, a significant runoff increase is discernible since the 1970s. Extreme value theory shows that recent high-discharge events have exceeded predictions based on 100-year long historical records and it is likely that a flood with, for instance, a 200-year return period will surpass anything calculated on the same basis. The analysis of the geochemical impact of 1982-83 El Niño-triggered extreme flooding, which apparently was the 100-year flood, illustrates that dissolved phases exported during the flood show different behaviors: some phases are non-linearly diluted whereas others increase concentration as flow increases. Major ion (alkaline and alkaline-earth elements) relationships were significantly altered during the event due to changes in major sources (e.g., Cl- and Na+ switched from continental sources, most likely marine sediments and other saline environments, during low-medium flow to rainfall-supplied marine aerosols during high discharge). A group of total heavy metals determined during the 1982-83 flood appeared to follow an ideal dilution pattern, where a doubling of discharge determines a one-half decrease in concentration
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| Format: | Digital revista |
| Language: | English |
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ASOCIACIÓN INTERCIENCIA
2007
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| Online Access: | http://ve.scielo.org/scielo.php?script=sci_arttext&pid=S0378-18442007001000004 |
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