Isotope tracing of the Paraná River, Argentina

PANARELLO, HECTOR; DAPEÑA, CRISTINA

Monitoring Isotopes in Rivers: Creation of the Global Network of Isotopes in Rivers (GNIR)

INTERNATIONAL ATOMIC ENERGY AGENCY

Lugar: Vienna; Año: 2012; p. 51 - 68

The Río de la Plata estuary is the collector of a vast drainage basin of about 3.1·106km2 There are many tributaries to the estuary but the Paraná and Uruguay rivers discharge directly more than the 99% of the average 24000 m3/s.We study the stable isotope compositions since 1997.  From 120 isotopic pairs, it could be established that 18O and 2H exhibit a cyclical pattern with maxima in November and minima in May.  Values are in correspondence with the ITCZ position.  When it is located near 8º N, the rain over the basin is lower and hence the isotopic composition of both elements is less depleted.  Conversely, when the ITCZ moves southwards, the pluviosity increases leading to 18O and 2H to more negative values.  This signal is recordered with a delay of  ca 4 month in the estuary.  The derivate magnitude, deuterium excess, showed important variations, from 1 to 18 per mil, being related the higher values to positive ENSO (El Niño) and the lower to negative ENSO (La Niña).  Despite all the interactions with groundwater and physical processes suffered along ca.2,800 km, the Paraná River still reflects at its mouth all these climatic phenomena that modified the 2H and 18O contents at its catchment areas