Hydrological impacts of deforestation on flow dynamics of small watersheds in the Brazilian Cerrado – Amazon transition region

• Deforestation led to consistently higher flows in the studied watersheds, especially during the wet season. • The impacts of land use change on the water cycle are more pronounced in watersheds with higher slopes. • Deforestation decreased the daily flow during the dry season, increasing water scarcity. • A higher percentage of deforestation in the watershed was strongly associated with higher storm flows. Understanding the effects of land use changes on hydrological cycling is essential for managing water resources. While deforestation is a known driver of hydrological regime shifts, few studies have assessed its impacts in the steep landscapes of the Brazilian Amazon-Cerrado transition, a region experiencing rapid deforestation and agricultural expansion. Here, we evaluate streamflow responses to land use and land cover changes using three years of field monitoring across eight watersheds (2.5 – 39 km 2 ) in eastern Mato Grosso, Brazil. Our study watersheds spanned a gradient of slopes (2% – 8.6%) and native vegetation cover (10% – 80%). Annual and daily flows were consistently higher in deforested watersheds, and these areas also exhibited greater flow seasonality and stormflow peaks. Notably, deforested watersheds experienced reduced baseflow during the dry season, increasing water scarcity at a critical period of the year. These findings highlight the importance of considering terrain slope and seasonal dynamics, because analyses at annual scales could mask the dual impacts of deforestation: increased flood risk during the rainy season and exacerbated water scarcity during the dry season. Our study highlights the value of integrating slopes, land cover, and multiyear data to support more effective water resource management in rapidly changing tropical landscapes.