Assessments of Climate change and sea level rise impacts on flows and saltwater intrusion in the Vu Gia - Thu Bon river basin, Vietnam

In recent years, besides the impacts of socio-economic development activities, climate change (including changes in rainfall and sea level rise) in the Vu Gia - Thu Bon river basin has directly affected water source security in the basin. Floods, droughts, and saline intrusion become irregular and increasingly serious, greatly affecting the supply of irrigation water for agricultural production and domestic use in the basin. In this study, we used a mathematical model to simulate changing flow patterns and saline intrusion in the river system in response to different climate change scenarios. Our modelling results show that the annual flow and the dry season flow in the basin tend to decrease under the pathway RCP 8.5 in the future periods 2030-2050, and the distribution of the flow varies among simulation periods and climate change scenarios. Although future flows at the end of century tend to increase due to the impact of climate change, the simulated results show that saline intrusion also increases in all scenarios. Under the RCP 8.5 pathway, on the Vu Gia river, the salinity concentration isoline of 1 ‰ intrudes into the river from 19.7 to 20.1 km, and 4 ‰ saline isoline from 18.4 to 20.8 km. On the Thu Bon river, the salinity isoline of 1‰ enters into the river from 18.6 to 20.3 km, and from 16.7 - 18.5 km for the salinity isoline of 4 ‰. Our results will be a scientific basis for decision making agencies to identify appropriate development strategies to adapt and mitigate negative impacts of climate change to ensure sustainable development at the basin.