EXTREMES OF PRECIPITATION AND FLOW ASSOCIATED WITH THE NATURAL AND ANTROPICAL CHARACTERISTICS OF THE HYDROGRAPHIC REGIONS OF SÃO FRANCISCO AND PARANÁ
Cluster Analysis, homogeneous sub-regions, theory of extreme values, overlay images
The occurrence of natural disasters due to the occurrence of extremes of precipitation and flow is becoming an increasingly common reality in the world. In most cases, the lack of prevention and mitigation plans associated with lack of management by public agencies maximizes damages and losses. In Brazil, hydrographic regions determine water management throughout the territory. However, it is worth emphasizing that the methodologies and solutions created to face such stresses are not necessarily the same for any region, given that each of them presents different characteristics in the economy, social, demographic and water management. In this context, this research aims to estimate the recurrence of extremes of intense precipitation and maximum flow, as well as to search for the existing relationship with the natural and anthropogenic characteristics in the hydrographic regions of São Francisco and Paraná. For this purpose, three datasets were used: meteorological, hydrological and demographic data with time series from 1988 to 2017. Observed data of precipitation were obtained from the National Institute of Meteorology and the National Water Agency. The flow data came from the National Water Agency. In addition, the information on demography extracted from the Brazilian Institute of Geography and Statistics. In the methodology, the descriptive statistics of the precipitation and flow data were used, together with the cluster analysis capable of identifying homogeneous sub regions of precipitation and flow in each hydrographic region. The generation of these homogeneous sub-regions was tested using the Silhouette Index. Subsequently, the subregions were inserted into the Extreme Value Theory in order to generate the estimation of the return periods of intense extreme precipitation and flow events. Subsequently, the overlapping of information on the physical, socioeconomic and demographic characteristics made possible the analysis of the use and occupation of the soil of susceptible areas. The results indicated the formation of four homogeneous sub-regions of precipitation in the two hydrographic regions studied, in addition to three homogeneous sub-regions of flow in the São Francisco hydrographic region and two in the Paraná hydrographic region. The scenarios for the recurrence of intense precipitation and maximum flow events indicate the high degree of severity by which certain subregions can be submitted. The use and occupation of the soil of these hydrographic regions has been changing abruptly in recent years. It should be emphasized that the urban growth of most cities and the change of natural areas for the practice of extensive agriculture can aggravate the numerous damages due to the scenarios for the two hydrographic regions.