Salinity intrusion in the Vietnamese Mekong Delta under upstream development, climate change and coastal engineering

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Salinity intrusion in the Mekong Delta: upstream development, sea-level rise and sluice gates. A modelling study co-authored by Dung Duc Tran (HAPRI Senior Research Associate) finds projected dry-season salinity in the Mekong Delta penetrates further and arrives earlier, and local sluice gates can push saltwater into adjacent branches. Dung Duc Tran (HAPRI Senior Research Associate) and co-authors. Illustrative photograph: a technician in a small boat on a Mekong Delta river branch lowers a handheld probe into the water to take a salinity reading. A concrete sluice gate and nipa palms stand along the bank.

Salinity intrusion in the Vietnamese Mekong Delta under upstream development, climate change and coastal engineering

www.hapri.org

Dung Duc Tran — Senior Research Associate

A modelling study co-authored by Dung Duc Tran (HAPRI Senior Research Associate) finds that projected dry-season scenarios for the Vietnamese Mekong Delta exhibit higher salinity, stronger penetration and earlier arrival times than the historical baseline and present-day conditions, with the most severe regional degradation when climate-driven sea-level rise coincides with intensive upstream water diversions. The simulations also expose an important hydrodynamic trade-off in coastal engineering.

Context

The Vietnamese Mekong Delta in Southern Vietnam is subject to salinity intrusion during the dry season, under changing inflows, climate scenarios and sea-level rise. Coastal engineering adds a further factor, as salinity-regulating sluice gates restrict natural channels in parts of the river network.

The study assesses and predicts the spatial and temporal dynamics of salinity intrusion under these conditions, considering the combined effects of upstream development, climate change and coastal engineering.

*Sluice gates curb salt locally, but can worsen it nearby*

Methods

The authors used the MIKE 11 hydrodynamic model, calibrated with 2016–2020 salinity data, to simulate dry-season (February–May) intrusion across nine scenarios: a historical 1998 baseline, 2020 present conditions, projected sea-level rise under RCP4.5 and RCP8.5, and a future combined upstream-development package that integrates full hydropower operations with moderate or high irrigation expansion. Three additional scenarios tested the effects of salinity-regulating sluice gates.

Key findings

Compared with the historical baseline and the present-day scenario, the projected scenarios exhibit higher salinity, stronger penetration and earlier arrival times, due to upstream alterations.
The most severe regional degradation occurs when climate-driven sea-level rise directly coincides with intensive upstream water diversions.
Under RCP4.5, the combined drivers paradoxically generate a larger area enclosed by the 2 PSU interpolated river-salinity surface than under the higher-emission RCP8.5, due to lower projected dry-season inflows.
Localized sluice gates successfully mitigate salinity on a local scale, but restricting these natural channels alters tidal distribution and can inadvertently intensify saltwater encroachment in adjacent, unfiltered river branches.

Keywords:

Salinity Intrusion
Vietnamese Mekong Delta
Hydrodynamic Modeling
Sea-Level Rise
Sluice Gates
Climate Change

Link:

https://doi.org/10.1016/j.ejrh.2026.104029

Citation:

Tran, D. D., Park, E., Thien, N. D., Kumar, S., Tho, T. Q., Thu, T. M., Hoang, L. P., Wang, J., & Tarolli, P. (2026). Salinity intrusion dynamics in the Vietnamese Mekong Delta: Combined effects of upstream development, climate change, and coastal engineering. Journal of Hydrology Regional Studies, 68, 104029.