Processos hidrológicos da bacia do rio Pajeú: revisão sistemática e uso do SWAT, e uma análise de tendências pelo método simplificado do balanço hídrico climatológico

Abstract

The impacts on hydrological processes on a regional scale, for example, with the reduction of water availability, can be caused by the removal of native vegetation and because of changes in land use and land cover. These processes, together with atmospheric phenomena, influence patterns of precipitation and potential evapotranspiration in the region. The Pajeú river sub-basin is one of the main tributaries of the watershed of the São Francisco river, with livestock as the main socioeconomic activity. Then, the objective was to analyze the uses and criteria applied in the hydrosedimentological model Soil and Water Assessment Tool (SWAT), calibrate and validate the SWAT from the data of watershed of Pajeú river and, through the simplified method of the climatological water balance, identify climatic trends and correlations of climatic variables with teleconnection indexes. Therefore, there was: 1) a systematic review that comprised the analysis of scientific articles between 2009 and 2019 in arid and semi-arid regions; 2) sensitivity analysis, calibration, validation and uncertainty analysis in the basin of the Pajeú river, using flow data; 3) analyzes of climatic trend and time series (Man-Kendall, Sen's Slope, Pettitt, Seasonal Trend decomposition using Loess) and 4) correlation between climatic variables and teleconnection indices with influence in the Pacific and Atlantic Oceans (Correlation Coefficient of Spearman). The SWAT model has been widely used in the management of land and water resources in river basins, including in arid and semi-arid regions. The steps of calibration, validation and uncertainty analysis were not satisfactory, presenting a better result only in a fluviometric station. The patterns of precipitation, evapotranspiration and climatic water balance have a significant impact on the hydrological cycle and, therefore, on the agricultural calendar of the sub-basin of the Pajeú river with greater interference from the phenomena of the Atlantic Multidecadal Oscillation, El Niño region N12 and the North Tropical Atlantic. It is concluded that advances with the application of SWAT in the sub-basin of the Pajeú river are still necessary, in particular, with improvements in the calibration and validation of the model, in order to deepen the knowledge about the relationship between the effects of changes in the land use and active atmospheric phenomena, and impacts on agricultural activities in the region.