Hydrological Simulation in the Corumbataí River Basin Using the SWAT Model: Simulation of Hydrological Variables and Land Use and Land Cover Scenarios

Hydrological modeling is a very relevant tool for planning and managing water resources because it considers the spatial and temporal distribution of hydrological processes and can be used for various purposes, such as estimating water availability, predicting flows, and analyzing the hydrological response of the basin as a result of changes in land use. The objective of this work was to calibrate and validate the Soil and Water Assessment Tool (SWAT) model for the Corumbataí River Basin, Brazil, and analyze the impacts of changing land use and land cover on the quality and quantity of water in the basin. Data on flow, total suspended solids, total phosphorus, and total nitrogen were calibrated and validated. The model’s performance was better in simulating flow on a monthly scale when compared with a daily scale, with Nash–Sutcliffe efficiency coefficient (NS) and R2 equal to 0.79 and PBIAS equal to 3.8% in the calibration and NS and R2 equal to 0.58 and PBIAS equal to 1.7% in the validation period. The PBIAS measures the average tendency of simulated values to be higher or lower than those observed and was the statistical index that best classified the model’s performance in nutrient simulation, thus indicating that nutrient values can be used when accumulated over time. Among the four alternative land use and land cover scenarios, Scenario 2 (pessimistic) resulted in greater sediment production and surface runoff in the basin. The results presented showed that the SWAT model was able to accurately simulate the variables involved in the calibration and validation process, proving to be a viable tool to support managers in the planning, management, and conservation of the Corumbataí River Basin, through scenario simulation alternative land use options, which highlighted the impacts that could be generated.