Quantifying the varying contributions of climate change, LUCC, and cascade reservoirs to hydrological regime alterations in a highly regulated basin

The middle and lower Hanjiang River (MLHR) basin, central China. Climate change and human activities, especially cascade reservoirs (CRs) construction and LUCC, have significantly disrupted natural hydrological regimes, leading to riverine ecosystem degradation in the study region. To precisely understand the hydrological impacts of these factors, this study provides a hydrological analysis framework that integrates the Soil and Water Assessment Tool (SWAT) and the Indicators of Hydrological Alteration–Range of Variability Approach (IHA-RVA). This framework is applied to quantitatively analyze their respective contributions, using 1961–1967 as the natural baseline for simulation and comparison. Results indicate a fundamental regime shift from natural seasonality to a static, reservoir-controlled state. CRs dominate regional hydrological alterations, contributing 60.88 % (1990–1999) and rising to 76.12 % (2000–2019). The seasonal flow regime was flattened by increasing winter–spring flows and extreme minimum flows, while reducing summer–fall flows and diminishing essential flood pulses. Climate change ranks second with contributions of 38.35 % and 22.60 %, slightly increasing winter and summer flows, while LUCC has minimal impact (60 %), surpassing climate change and LUCC. • Restoring flood pulses is key for adaptive reservoir management.