Interannual and Interdecadic Climatic Variability in Rio Iguazu basin

In this work, space and temporal dominant patterns of the interannual, decadic and interdecadic variability associated to the precipitation fluctuations and superficial runoff were identified in the Río Iguazú basin (64.000 km2), in the Southeast of South America.

The most significant climatic fluctuations in the present century as much in flows as in precipitations were detected and analyse. The series of flows correspond to the period 1931-1992 and those of precipitations to the period 1901-1995.

The network of acquisition of precipitation data is formed by more than 50 rain gauges of monthly information. These points conform a virtual network generated starting from the real network of data acquisition. Nine gauge stations on the main channel and the most important tributaries in the Iguazú River for the surface runoff analysis at monthly level were used.

The dominant temporary patterns found correspond to time scales of approximately 8, 3.2 and 3 years as dominant frequencies as much in the precipitations as in the surface runoff.

In the domain of the low frequencies of the precipitations is present the period of 64 and 32 years, while in the runoff the level of significance is not reached, although it is close to it at the whole network.

Four periods of different climatic characteristics were identified: the first period (1901-1930), with relative wet conditions; the second period embraces from 1931 to 1970, with relative dry conditions; the third period (1971 - 1980), with wet conditions, and the last period (1980-1991), with extremely wet conditions.