Abstract The knowledge of the frequency and magnitude of low flow events is necessary to mitigate social, economic and ecological impacts inside the basin. However, the measurement network in Brazil is still restricted to large drainage areas, while basins with less than 300 km2 remain ungauged. Among different flow estimation methods, we used a rainfall-runoff model designed specifically to estimate flow rates during the dry season in small ungauged basins: the Silveira Method (SM). We tested the model performance for the São Bartolomeu river basin (Minas Gerais, Brazil), a small ungauged basin that experienced severe droughts and water supply shortages in 2014-2016. We tested eleven different scenarios based on the time and duration of drought periods used to estimate the model parameters. In the best scenario, the model underestimated low flow rates by 31% for Q95 and was considered suitable to predict local low flow. Finally, the model results suggest that a water volume higher than the river can support has been granted concession during the dry season, which may lead to an unsustainable water supply scenario soon. This result showed the capacity of SM as a complementary tool for the evaluation of water potential in small basins.