Análise da variabilidade espaço-temporal da precipitação pluviométrica na bacia do Rio Mourão - PR

Abstract

The climate, and especially rainfall, has direct influence on hydrological cycle, imposing limitations to anthropic activities, mainly agriculture. Therefore, studying the regional rainfall pattern assists on appropriate planning and zoning of economic activities and environmental preservation. Thus, this work has as its objective to analyze the spatial and temporal variability of pluviometric precipitation on Mourão river basin, located on Midwest of Paraná. To do this, monthly data from 13 selected pluviometric stations were analyzed, on the period from 1980 to 2012, obtained with Instituto das Águas do Paraná (Paraná Waters Institute). Data were organized on spreadsheets and standardized, filling existing failures to allow the calculation of descriptive statistics, by the parameters of average, standard deviation and variation coefficient. Obtained values were analyzed on monthly, seasonal, annual and interannual scales, by graphics and isohyet maps elaborated by interpolation via the kringing method. Yearly totals went through cluster analysis, where the pluviometric stations formed similar groups, that were spatialized. The interannual variations were observed with a spatiotemporal panel, where years were classified in each station, and then four years were selected for further analysis. In all performed analysis, the lack of data on the basin central portion was a limiting factor to analyze spatial variation of rainfall with precision. On monthly analysis, the driest month to all stations was August, reaching around 65 mm on north of the basin, while the rainiest month varied between January (9 stations), October (3 stations) and December (1 station), with maximum values close to 230 mm. On seasonal scale, spring and summer showed values close to 600 mm on south of the basin, spring being rainier on 7 stations, and summer on 6. Winter was the driest season in all cases. On yearly scale, the average value was of 1753,7 mm, varying between 1242,2 mm, in 1983, and 2556,9 mm, in 1988. There was a general tendency of decrease of rainfall values towards the north, caused by the gradual difference of altitude, besides the influence of transition between tropical and subtropical climates in this region. This differentiation was also obtained on cluster analysis, that obtained two homogeneous groups, with distinct patterns between upstream and downstream. From the spatiotemporal precipitation panel, it was chosen one rainy pattern year (1990), one tending to rainy (1998), one dry (1988) and one tending to dry (1999). In all these years, the rainfall patterns got away from the average values, with both spatial and temporal variations, related to the influence of atmospheric circulation phenomena, like El Niño and La Niña, causing different spatiotemporal distribution patterns on atypical years.