Projections of salt intrusion in a mega-delta under climatic and anthropogenic stressors

Rising temperatures, rapid urbanization and soaring demand for natural resources threaten deltas worldwide and make them vulnerable to rising seas, subsidence, droughts, floods, and salt intrusion. However, climate change projections in deltas often address climate-driven stressors in isolation and disregard parallel anthropogenic processes, leading to insufficient socio-political drive. Here, using a combination of process-based numerical models that integrate both climatic and anthropogenic environmental stressors, we project salt intrusion within the Mekong mega-Delta, in the next three decades. We assess the relative effects of various drivers and show that anthropogenic forces such as groundwater extraction-induced subsidence and riverbed level incisions due to sediment starvation can increase the salinity-affected areas by 10-27% compared to the present-day situation, while future sea level rise adds another 6-19% increase. These projections provide crucial input for adaptation policy development in the Mekong Delta and the methodology inspires future systemic studies of environmental changes in other deltas. Human activities, such as groundwater extraction and sediment starvation, are projected to add to climatic factors like sea level rise to exacerbate saline water intrusion into the Mekong Delta, Vietnam over the next 30 years, according to process-based model simulations.