Shifting water and energy controls on hydrological processes under climate change in the topographically complex Min–Tuo River Basin, southwest China

The Min–Tuo River Basin, located in the upper Yangtze River Basin, southwest China, features strong topographic relief, large elevation gradients, and complex hydroclimatic conditions. This study applied the Geomorphology-Based EcoHydrological Model (GBEHM) to investigate the hydroclimatic changes and the evolution of hydrological sensitivities to climatic drivers in the Min–Tuo River Basin during 1980–2019. In a warming and wetting climate during 1980–2019, the annual evapotranspiration (ET) increased by 1.54 mm yr −1 , whereas the annual runoff declined by 1.20 mm yr −1 in the study basin. The interannual runoff variability is sensitive to precipitation, while rising temperature enhances ET and suppresses runoff, suggesting intensified evaporative losses. Beyond climatic drivers, human activities appear to dominate the observed runoff decline, indicated by a large residual term in attribution analysis. During the past 40 years, runoff elasticity to precipitation decreased by 0.01 mm mm −1 per decade, whereas ET elasticity to temperature increased by 4.03 mm °C⁻¹ per decade. Meanwhile, the runoff–temperature elasticity became increasingly negative (−4.02 mm °C⁻¹ per decade), indicating a stronger negative runoff sensitivity to warming. These findings highlight a progressive shift from water-limited to energy-limited hydrological conditions under persistent warming, particularly in downstream lowland plains. This study advances understanding of how water–energy coupling regulates hydrological processes in topographically complex basins under climate change. • Warming and wetting enhanced evapotranspiration but reduced runoff in the past 40 years. • Hydrological trends and climatic responses showed clear elevation dependency. • Runoff showed decreasing sensitivity to precipitation and stronger negative sensitivity to temperature. • Hydrological regime shifted from water- to energy-limited under persistent warming.