Salinity Intrusion Is Rising in Ben Tre, Complicating Freshwater Exploitation in the Mekong Delta

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Salinity intrusion is rising in Ben Tre, complicating freshwater exploitation. Over the last 25 years, salinity intrusion in Ben Tre Province has progressively increased and started earlier in the dry season. Modelling anticipates it reaching further inland by 2030, even with comprehensive water infrastructure. Dung Duc Tran (HAPRI Senior Research Associate) and co-authors. Illustrative photograph: a farmer in a coconut-growing Mekong Delta hamlet tests canal water with a handheld salinity meter during the dry season, beside a small pump and large water-storage jars.

Salinity Intrusion Is Rising in Ben Tre, Complicating Freshwater Exploitation in the Mekong Delta

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Dung Duc Tran — Senior Research Associate

A study co-authored by Dung Duc Tran (HAPRI Senior Research Associate) and colleagues finds that, over the last 25 years, salinity intrusion in Ben Tre Province has progressively increased and started earlier in the dry season. Its modelling scenarios reveal a growing complexity in the exploitation of freshwater resources, with challenges related to timing, depth and geographical location.

Context

Climate change-driven sea level rise has intensified salinity intrusion in deltas worldwide, posing significant threats to the exploitation of freshwater resources. In the Vietnamese Mekong Delta, the third largest delta globally, salinity intrusion is a recurring challenge along the coastline, degrading freshwater resources for agricultural and domestic use and affecting socio-economic development.

The study focuses on Ben Tre Province, which the authors describe as the hotspot of salinity disaster within the Vietnamese Mekong Delta.

*How salinity is distributed through the dry season*

Methods

The authors analysed long-term salinity monitoring data covering 25 years, from 1996 to 2020, and developed a 1D hydrodynamic model (Mike 11) coupled with a 3D hydrodynamic model (Mike 3). They used three scenarios to investigate freshwater exploitation: the year of investigation (2021); climate change impacts from 2021 to 2030 under different annual exceedance probabilities of the upstream Mekong discharge (average flow, relatively low, low and very low); and extreme salinity intrusion, represented by the 2016 condition.

Key findings

Salinity patterns were well-stratified at the beginning and end of the dry season but well-mixed during the middle period.
Over the last 25 years, salinity intrusion has progressively increased and started earlier in the dry season.
The exceedance probability scenarios, ranging from 50 % to 95 %, disclosed higher and deeper salinity intrusion along the channel in the Vietnamese Mekong Delta.
Under the current trajectory of climate change, the 2030 scenario anticipates salinity intrusion reaching further inland than in the 2021 scenario.

Keywords:

Salinity Intrusion
Vietnamese Mekong Delta
Ben Tre Province
Freshwater Exploitation
Hydrodynamic Modeling
Climate Change

Link:

https://doi.org/10.1016/j.jhydrol.2024.130655

Citation:

Tran, D. D., Thuc, P. T. B., Park, E., Hang, P. T. T., Man, D. B., & Wang, J. (2024). Extent of saltwater intrusion and freshwater exploitability in the coastal Vietnamese Mekong Delta assessed by gauging records and numerical simulations. Journal of Hydrology, 630, 130655.