Estudo comparativo e delineamento de índices de aridez na sub-bacia do Alto Paraíba - PB.

Abstract

Considering the relevance of understanding the Aridity Index (IA) since it is related to the susceptibility to desertification, the objective of this work was to map and compare the Aridity Indices in the Paraíba River Watershed, specifically the IA in the sub-basin of Alto Paraíba-PB. In order to determine the Aridity Index in the Alto Paraíba-PB Sub- Basin, we obtained the annual total rainfall and estimated potential evapotranspiration, calculated by the Thornthwaite & Mather method (1955). From the calculation of the Aridity Index the risks to desertification were determined, as well as the climatic classification that defines the climatic zones established by UNEP (1991). Thus, the indices varied, as for the climatic classes for aridity, as follows: less than 0.03 (<0.03) Hyperarido; 0.03 to 0.20 Arid; 0.21 to 0.50 Semi-arid; 0.51 to 0.61 Subhumid and Dry; and greater than 0.65 (> 0.65) Subhumid and Wet. For the production of maps, data from the census of the Brazilian Institute of Geography and Statistics (IBGE) were used, which assisted both in mapping and interpretation of data. After the aridity indexes were prepared, a spreadsheet with the data obtained and its geolocations (latitude and longitude) was elaborated and using the Surfer 7.0 software, the statistics were performed using the Krigagem type interpolation methodology, where the distribution map and trimmed using the boundary of the microregion under study. In order to analyze the spatial distribution of the data, the interpolation method called Kriging was used to determine the mean, standard deviation, variance and coefficient of variation. It was concluded that in spite of the relatively flat relief in certain places, the Alto do Paraíba Sub-Basin presents classification classes in transition between terrains with marked slope. As for erosivity, it shows its maximum when observed between coasts ranging from 400 to 480 meters above sea level. Regarding the Aridity Index (IA), the Sub-Basin considering the levels of susceptibility to desertification established from Aridity Index values is moderate to high.