Assessment of impacts on basin stream flow derived from medium-term sugarcane expansion scenarios in Brazil

This study assessed the effects of land use changes driven by sugarcane expansion on the stream flow for two selected basins: Monte Mor (MM), where a stagnation in sugarcane area is expected, and Fazenda Monte Alegre (FMA), which is under intense expansion towards the Cerrado biome. The evaluation was made using a previously calibrated and validated SWAT model. Scenarios of land use changes were made based on a more realistic sugarcane expansion related to future ethanol demand and also regarding more intense expansion and other land use change trends, always considering the maintenance of natural vegetation. Modelling results show that the expected sugarcane expansion for 2030 would not bring substantial impacts on stream flow, nor on the reference flow (Q90) in flow duration curves for MM basin. For FMA basin, the expansion is expected to increase stream flow and reference flow during the dry season and decrease during the rainy season. The results suggest that the replacement of annual crops and pasture lands by sugarcane regulates the stream flow regime by decreasing stream flow peaks and, consequently, the flood risk, while also increasing water availability during the dry season.