THE TEMPORAL CLIMATIC VARIABILITY IN THE RIO-DE-LA-PLATA BASIN DISPLAYED BY THE RIVER DISCHARGES

Streamflows have a direct dependence on precipitation and these are di rectly linked to climate. Then, in this paper the temporal climatic va riability in the 'Rio de la Plata' Basin is analysed through the chang es in the river's discharges. These are the reflection of the climatic inputs areally integrated, and in consequence, contain more informati on on climate variability than that provided by the scarce punctual re cords of precipitation and temperature. The time series of streamflows correspond to monthly and annual means in stations selected in the ba sin for the period 1931-1992. However, in the present paper, the perio d 1901-1992 was considered in all cases whenever possible. The followi ng changes and tendencies in the flow series were detected: 1. An impo rtant change of tendency between 1970 and 1972, and another not so sig nificant before that date were detected in 1917-1918 and 1943-1944. 2. The jumps in the means in several sub-periods were detected using dif ferent methods, They showed jumps mainly in the period 1970-1972 in th e annual streamflows series. The jumps in the annual streamflow series consist of an abrupt change in climatic variables affecting temporari ly the averages of such variables during a certain period of time (yea rs). The results are consistent with the conclusions obtained by other authors for the same region, both in precipitation and in the general circulation of the atmosphere. Keeping in mind this analysis of the s eries of streamflows, indicators of normal variability of tendencies r elative to natural regional causes were detected, although the local c auses were not anthropogenically analysed, and so no other manifestati ons of randomless in the zone of the Basin under study because of the lacking of data.