The present study uses a semi-distributed hydrological model to predict streamflow within Lower Godavari River Basin. The Soil and Water Assessment Tool (SWAT) has been utilized to understand and replicate the basin’s intricate hydrological mechanisms by incorporating meteorological data, land use information, and soil properties into the ArcSWAT interface within ArcGIS. Sensitivity analysis using the SWAT-CUP software and SUFI-2 methodology identifies the model parameters that have the most effects on catchment flow. The model is calibrated and validated using a comprehensive dataset covering 38 years, from 1982 to 2020. The results indicate that the SWAT model exhibits strong and consistent performance in effectively replicating the channel runoff. The correlation between the predicted and observed values for the calibration period spanning from 1984 to 2014 is 89%, and for the validation period from 2015 to 2020, it is 85%. The model’s effectiveness is supported by the Nash–Sutcliffe Efficiency (NSE) values of 0.86 during calibration and 0.82 for the validation. The present study’s findings provide valuable insights into water resource management and hydrologic modeling involving complex hydrological processes. The presented results can help in decision-making for sustainable water resource planning and utilization.