Caracterização espaço-temporal dos regimes pluviométricos e hidrológicos do baixo rio Iguaçu (1976-2016).

Abstract

The drainage basin of lower Iguaçu is located in the Southwest of Paraná and over the years, due to the growth of the cities and the concentration of meatpacking plants, it started to present great importance in agriculture and cattle raising, in urban supply, and in electricity generation (i.e the creation of hydroelectric power plants - HPP). These sectors of the economy require constant water demand, so characterizing the rainfall and hydrological regime represents an important step to assist in the development of the region. Combined with that, there are few works that address the lower Iguaçu. Thus, the researches that deal with the Iguaçu River, focus on the upper Iguaçu, for supplying the metropolitan region of Curitiba. Based on the above, this work aims to characterize the hydrological and rainfall regime of the lower Iguaçu River from 1976 to 2016. To fulfill this objective, in the rainfall regime the kriging method was used in order to spatialize the rain data from 30 rainfall stations and the statistical parameters to observe trends. To verify the influence of El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), the variation in "Sea Surface Temperature" was compared with the data plotted on the precipitation maps. The analysis of the standard years helped to identify rainfall patterns. Concerning the hydrological regime, it was characterized and analyzed through the daily flow regime of 10 fluviometric stations, in which it was observed the stationarity and periodicity, frequency of flows, recurrence (period of return of maximum flows) and classification of floods. Finally, the results of the above-mentioned procedures indicate that ENSO events with strong intensity show above-average rainfall in practically the entire area of the lower Iguaçu River. This statement, however, does not add up to the events of La Niña, since no episode of strong intensity occurred during the period studied. Events of moderate intensity do not necessarily cause a reduction (La Niña) or increase (El Niño) of precipitations, sometimes they may vary above, below or near the average without characterizing a trend. The PDO followed the trends in its phases, cold (1976-1978 and 1999-2016) and hot (1979-1998), with an increase in El Niño (hot) and La Niña (cold) events. On the other hand, the river regime oscillated significantly in the studied period, without showing periodicity. The floods of the Iguaçu River are concentrated in the rainy years of the series, the dry years, however, are not just concentrated in the episodes of La Niña, following the trends already discussed in the rain regime.