Abstract
AbstractWater resources management and agriculture planning models require a statistical synthesis of some rainfall features, in particular those representing dry atmospheric conditions. The bigger the basin, the more important these features become, as is the case of the La Plata Basin (LPB).This paper focuses on the precipitation variability in the large LPB in South America, analysing the number of months per year with low rainfall and the sequences of months with low rainfall, their theoretical distributions and stability, which are needed as input for the models mentioned above.Long time series are used to analyse the low‐frequency variability and the relative importance of decadal variability. Changes are evident in the number of months per year with low rainfall, with a decrease of about 20% in the period after 1970.Theoretical distribution models (binomial and geometric) are fitted to these empirical distributions, and the regional variability of the fitting parameters is shown. In practically the entire region, the goodness‐of‐fit of the two theoretical models considered is statistically satisfactory.The temporal variability of the parameters of the theoretical binomial (p) and geometric (α) distributions is analysed, in excluding sub‐periods of 10 and 5 years, respectively. The results show low‐frequency variability overlapped on a decadal variability, with low homogeneous regional behaviour.The distribution models have proven to be efficient for frequency adjustments of the rainfall properties studied. These results are an acceptable and necessary input to decision models in LPB. They also make it possible to infer effects of climate change. Copyright © 2008 Royal Meteorological Society
Highlights
La Plata Basin (LPB), which covers parts of Argentina, Brazil, Bolivia, Paraguay and Uruguay, is the third largest basin in the world with an area of approximately 3 200 000 km2 (Garcıa and Vargas, 1998)
Several authors have observed jumps and/or trends in the annual rainfall totals in the study region, which were generally related with the annual rainfall and some particular months or seasons of the year
Some decision-making models in hydrology, as well as in other activities, need a very stable input, in terms of rainfall information, which needs to be synthesized from specific features
Summary
La Plata Basin (LPB), which covers parts of Argentina, Brazil, Bolivia, Paraguay and Uruguay, is the third largest basin in the world with an area of approximately 3 200 000 km (Garcıa and Vargas, 1998). The basin generates around 70% of the Gross National Product (GNP) of these five countries, and has a population of over 100 million inhabitants. The LPB is one of the major producers of hydroelectric power in the world. The LPB comprises the catchments of three large rivers: Paraguay, Paranaand Uruguay. The last two join to form the La Plata River, while the Paraguay flows into the Paranaa few kilometres upstream from the city of Corrientes in NE Argentina. The topography and climate of the region, as well as precipitation and human activities, strongly influence the hydrological behaviour of the rivers in the basin.
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