Análise das frequências de secas na bacia hidrográfica do açude Epitácio Pessoa-PB.

Abstract

The Brazilian semi-arid region (SAB) is frequently reach by drought events. Drought, although recurrent, affects a large number of people and; the economic activities in SAB is a climatic event that still needs to be better studied. The objective of this work was to adjust the characteristics of the drought: Severity, Duration and Intensity in the SAB. As a planning unit, the water catchment area of the Epitácio Pessoa dam was chosen, a watershed representative of the SAB. This basin is located in the Paraíba state, in the SAB. The precipitated monthly totals were collected, collected in the 30 rain stations with sample size of 40 years. The adjustments of the probability distribution functions to the values of the drought characteristics: Severity, Duration and Intensity for each of the subregions were considered satisfactory. The adherence of the curves in each subregion showed that each of them has particular characteristics, mainly in relation to rainfall data quality in the rainy season and the size of the sample space. The three homogeneous sub-regions, according to the characteristics of the drought (Severity, Duration and Intensity) were precisely delimited by the multivariate statistics denominated Cluster Analysis, sub-regionalizing the characteristics of drought and providing the subsamples for their modeling by the use of the equations of regression for each sub-region. The results of the adjustments of the multiple linear regression equations for the entire Brazilian semi-arid region follow the standards presented for the locations within the Epitácio Pessoa basin. In this basin subregions 1 and 2 presented very good results for the relational estimates of drought characteristics: Severity, Duration and Intensity. The subregion three did not present satisfactory results. Basically, this proportion of two-thirds of positive results and one-third negative can be extended to the entire semi-arid region of Brazil. The proportion of negative results occurs when the interactions between the characteristics of the drought (Severity, Duration and intensity) are very heterogeneous.