Spatiotemporal evolution of ecological risks in the Yarlung Zangbo River basin: Implications for sustainable hydropower

Recent hydropower acceleration in developing countries reveals a key issue: many projects lack basin-wide environmental impact assessments pre-development. As an international waterway, the Yarlung Zangbo River faces similar challenges, underscoring the urgent need for pre-project ecological risk assessments. This study proposes a new ecological risk assessment method combining landscape ecological risk with hydrological risk, using the space-time cube (STC) approach to detect risk trends, focusing on hydropower-controlled watersheds. Results show that from 2002 to 2022, the average ecological risk in the Yarlung Zangbo River basin decreased from 0.515 to 0.498, with high-risk areas dropping from 51.03 % to 29.14 %, mainly in the east and center. The southeast maintained low risk, while the northwest exhibited higher risk. Persistent hotspots of ecological risk (21.96 % of the area) were concentrated in the west and center, while cold spots (11.58 %) were more common in the east. Watersheds managed by hydropower stations showed a steady decline in ecological risk, with low-risk areas peaking in 2022, suggesting stable or improved operational safety. This study provides a novel concise and efficient preliminary assessment methodology for basin ecological risk, uncovering ecological risk patterns in the Yarlung Zangbo River basin and supporting hydrological policy development and sustainable hydropower development. • A new ecological risk index tailored to hydropower development basins was developed. • The index integrates landscape ecological risk and hydrological risk. • The space-time cube (STC) method is introduced to elucidate ecological risk dynamics. • The ecological risks in the Yarlung Zangbo River basin from 2002 to 2022 were studied. • The ecological risk in the watershed upstream of the hydropower stations declined.