Strategizing renewable energy transitions to preserve sediment transport integrity

Abstract

Hydropower is vital for climate mitigation by enabling low-carbon energy systems, but hydropower dams also trap sediment, a crucial resource for ecosystems and climate adaptation along downstream coastlines. Here we present a multisectoral integrated water–sediment–energy planning framework that fully internalizes the impacts of hydropower expansion, both on energy system costs and on foregone ecosystem services from reduced sediment supply for the Mekong River Basin. Our analysis indicates that full development of large hydropower could reduce sediment flows to the Mekong Delta by 41.2 ± 6.6 megatonnes per year (75 ± 9%). However, strategically replacing 19 high-sediment-trapping hydropower plants with solar, wind and energy storage alternatives could preserve up to 98% of sediment supply, with only a 4–6% (US$15.7–26.0 billion) increase in energy system costs over 2020–2050. Crucially, when sediment-related benefits—valued at US$12–28 million per megatonne per year—are considered, the additional costs of preserving sediment supply are nearly offset. The proposed framework offers a transferable approach to support sustainable low-carbon energy transitions while safeguarding sediment-dependent ecosystems worldwide.