Natural events and anthropogenic activities are the two major driving forces that alter hydrological cycle processes, leading to hydrological extreme events such as floods and droughts. Streamflows are directly influenced by these forces, however, their cumulative effects over time are considered as indirect effects. This study investigated the distinct effects of precipitation, temperature, and human activities on hydrological droughts in five major river basins in South Korea. Change points in the hydrological data were identified after the 1990s in all basins by the sequential Mann-Kendall test. We used two water balance models, the ABCD and the GR2M, in this study, and their integration was used for streamflow simulations. We applied the standardized runoff index (SRI) to identify hydrological drought under different data-driven scenarios (climate change, constant temperature with varying precipitation, constant precipitation with varying temperature, and human influence). Natural and anthropogenic variations had a greater effect on drought severity than on drought duration. Variation in precipitation increased streamflow by 12.42%, followed by human activity at 0.71%; temperature decreased streamflow by -0.7% on average. Precipitation was a dominant factor that increased drought severity by 41.38%, followed by human activity at 15.85%; temperature decreased drought severity by -0.86% on average. This study improves understanding of the response of streamflow and hydrological drought to precipitation, temperature, and human activities, which is beneficial for decision makers and water managers in developing adaptive strategies to alleviate extreme natural disasters.