Banca de DEFESA: GEORGE ANTONIO JANGARELLI

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : GEORGE ANTONIO JANGARELLI
DATE: 28/08/2023
TIME: 14:00
LOCAL: IGDEMA
TITLE:

RAIN AND FLUVIAL VARIABILITIES IN THE PHYSIOGRAPHICAL REGION OF LOW SÃO FRANCISCO

KEY WORDS:

rainfall, flow, hydrographic basin, semi-arid.

PAGES: 82
BIG AREA: Ciências Humanas
AREA: Geografia
SUMMARY:

Recent studies have been pointing out that ongoing climate changes may result in a reduction in rainfall and an increase in droughts in the Brazilian Northeast, thus aggravating the situation of water vulnerability, especially in areas that already present a certain degree of susceptibility, as is the case of the Region of Lower San Francisco (RBS). Aiming to contribute to facing these questions, the main objective of this work was to characterize the variability and significant trends of rainfall and flows in the physiographic region of the Lower São Francisco. To analyze rainfall variability and trends, a series of monthly rainfall data from 1980 to 2013 was used, whose data were extracted from 39 points of the RBS, from the database of Xavier et al. (2016). To analyze the variability and fluvial trends of the lower course of the São Francisco River, monthly data obtained from the ANA (National Water Agency) database referring to the period from 1982 to 2020 were used, extracted from three points (Piranhas/AL , Pão de Açúcar/AL and Propriá/SE). Descriptive statistics were calculated and the non-parametric Mann-Kendall test was applied to identify trends in rainfall and discharges. The adopted statistical significance was 10, 5 and/or 1%. The results of the analysis of rainfall variability showed that the region has higher amounts of precipitation from April to July, and lower from September to December. For annual precipitation, accumulations ranging from 522 mm to 1241 mm were identified to the west and southeast of the RBS, respectively. The analysis of standard years showed precipitation amounts ranging from 230 mm to 1,100 mm in the dry year (1993), 230 mm to 1,390 mm in the usual year (1984) and from 520 mm to 1,982 mm in the rainy year (1989). In turn, the application of the Mann-Kendall test showed trends of increased precipitation in the two temporal scales analyzed. On the annual scale, an increase in the order of 5.4 to 11.2 mm per year was observed in 28% of the points, which are located in parts of the western, central, eastern and southeastern portions of the RBS. On a seasonal scale, the winter season showed significant trends of increased precipitation of the order of 3.2 to 5.2 mm in 18% of the stations analyzed, which are located in parts of the western, central and eastern portions of the RBS. The analysis of average monthly flows showed that the highest flows occur from January to April, with a variation between 2,040 and 2,470 m³/s, and the lowest occur from June to August, with a variation between 1,520 and 1,727 m³/s. Average monthly flows showed significant negative trends, with higher reductions between January and April. The average annual flows also showed a downward trend, with amounts varying between -35.84 m³/s and -42.53 m³/s. Finally, it was found that the flow regime has been strongly affected by flow regulation, which has culminated in the reduction of flood and drought periods and has also led to more severe reductions, as observed between 2013 and 2019, when the outflows to Sobradinho were continually lowered, leading to a series of socio-environmental impacts on the RBS.

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Interno(a) - 1891214 - KLEYTHON DE ARAUJO MONTEIRO
Presidente - 2501620 - MELCHIOR CARLOS DO NASCIMENTO
Externo(a) à Instituição - REBECCA LUNA LUCENA - UFRN