Modelagem hidrológica da bacia hidrográfica do alto Jaguaribe utilizando CN3S E SMAP

Abstract

This study analyzed the use of the CN3S (Curve Number - Three Steps) and SMAP (Soil Moisture Accounting Procedure) hydrological models to simulate surface runoff in basins in the semiarid region of Ceará. The use of rainfall-runoff models is essential for understanding the relationship between precipitation and streamflow, supporting water resource planning and management, and providing data for decision-making, especially in regions with large rainfall variations. The Arneiroz and Iguatu basins, located in the upper reaches of the Jaguaribe River, were studied using monthly rainfall and streamflow data from 1974 to 2012. The model was adjusted and verified using the solver tool in Excel, with the Nash-Sutcliffe coefficient (NSE) as the functional target. The CN3S results were then compared with the SMAP model, which is commonly used in Ceará. The CN3S performed satisfactorily in both basins, with NSEs greater than 0.67 and reduced MSEs. The results indicated that the CN3S model performed better overall, especially during the simulation of flood peaks, demonstrating greater sensitivity to precipitation variations. The SMAP model, although presenting good results, tended to smooth out hydrological extremes. In the Arneiroz basin, the CN3S achieved better NSE values in both calibration and validation. In the Iguatu basin, the performance of the two models was more balanced, but the CN3S showed a slight superiority in representing hydrological dynamics. It is concluded that both models are suitable for the hydrological conditions of the analyzed basins, with the CN3S demonstrating greater sensitivity to extreme events, demonstrating its usefulness for analyses in semiarid areas, such as Northeast Brazil.