Impacts of sugarcane expansion on water availability in a river basin in southeastern Brazil

Abstract

The availability of land, favorable edaphoclimatic conditions, and water have consolidated the role of Brazil as a global player in the agricultural commodities market, which has driven intensive land use conversion in recent decades. In this context, the extensive use of biofuels to mitigate fossil fuel CO2 emissions has facilitated their replacement as pasture by sugarcane monoculture, particularly in São Paulo State that is responsible for more than 52% of the country’s sugarcane production. This expansion has occurred without evaluating its impact on water availability for other uses. Therefore, this study investigates the effects of the sugarcane expansion on the hydrological cycle of the Aguapeí River basin in São Paulo State, during 1985–2017. To achieve this goal, we first validated the hydrological model simulation by comparing the time trajectories within the Budyko framework for the sub-basin with the longest observation records. We then assessed the impact of the expansion of the area under sugarcane by comparing the streamflow over the study period against a baseline scenario, which assumed that no land use changes occurred after 1985 in six sub-basins of the Aguapeí River basin. The results revealed a reduction in streamflow with sugarcane expansion. Although these changes corresponded to only 2–5% of the mean streamflow of the baseline scenario, these can increase to 13–27% when the effect of sugarcane expansion is isolated. Our results suggested that the impacts of sugarcane on streamflow are gradually diluted at larger scales. We also estimated that the extra water consumption due to the sugarcane expansion in São Paulo State was 2150 hm3 yr−1 in 2017 compared to 1985.