The multinational Paraná River (drainage basin, ~2.6 106 km2; annual discharge, ~500 km3 y-1) has a long (~900 km) and wide (~30 – 50 km) flood valley, which occupies its middle and lower stretches. Most of the valley’s area (estimated area of ~50000 kmkm2) holds a myriad of ponds, ox-bows, and channels which, following the seasonal variation of the prevailing discharge regime, exchanges water, dissolved species, sediment, and biological materials with the Paraná’s main stem. Exceptional hydrological events (e.g., ENSO-triggered) flood almost totally the expanse of the flood valley. A ten year-long (1965 – 1975) continuous series of alkalinity measurements allowed probing into the mechanisms that determine the observed alkalinity variability -controlled by several biogeochemical processes (e.g., photosynthesis/respiration, nitrification/denitrification, etc.) occurring in the riparian environment-, which are associated with the Paraná’s hydrological stage.
Centro de Investigaciones Geológicas