The lower Yalong River Basin is an important clean-energy base in China and an ecologically fragile mountain basin. Under rapid cascade hydropower development, the relationship between hydropower development stages and long-term watershed carbon storage changes remains unclear. This study assessed carbon storage dynamics in the lower Yalong River Basin from 1986 to 2021 using Landsat imagery, random forest land-use classification, and the InVEST carbon storage model. A stage-based assessment app