Modelagem hidrológica de três bacias hidrográficas do alto e médio Pajeú, estado de Pernambuco

Abstract

Understanding hydrological processes is fundamental in environmental studies, although little is known about the interactions between vegetation and soils in a watershed with hydrological regimes in Brazilian semi-arid environments. The present work proposed to apply and measure the performance of different methods of hydrological modeling (Number Curve, Rational Method, Modified Rational, I Pai Wu and the TR-55) in three sub-basins inserted in the Upper and Middle Pajeú regions, being the Riacho Exú, Riacho Cachoeira and Riacho Jacu basins. The actual flows considered were obtained through measurement campaigns, carried out in 2009 and extrapolated through theoretical models of Probability. The input data for the models were obtained through the analysis of vegetation cover (presence and use) and soil (occupation and use), carried out from secondary data and geoprocessing techniques. The five models used were tested respecting the recommendations inherent to the intrinsic particularities of each one of them. The statistical distribution that best allowed the extrapolation of the observed data were the Gama model was the one that best adjusted to the data from the Exú stream basins (r=0.99; χ²=20.071) and Cachoeira (r=0.982; χ²=0.058), and the Log-Normal obtained a better fit for the Jacú stream basin (r=0.968; χ²=0.045). The error and efficiency metrics indicated that for the Exú stream basin, the curve number moledo presented a better fit and a smaller error (NS=0,997 e MPE=-0,871). For the Cachoeira stream basin, the most appropriate modeling was due to the Modified Rational model (NS= 0,995 e MPE=-1,067). The Jacú, in turn, presented a more adjusted modeling for the Racional model (NS=0,993 e MPE=-1,247). The performance evaluations indicated that the more traditionally disseminated modeling (Number Curve and the Rational Method) presented more consistent results, highlighting that the present work contributed to the deepening of the knowledge of the existing hydrological characteristics in the Pajeú microbasins, as well as in the definition of the methods more suitable for the application of hydrological models in semi-arid environments, collaborating with the development of soil and water conservation techniques.