The document summarizes research on tidal propagation and salt intrusion in the Mekong Delta estuarine system in Vietnam. Field measurements were taken to study how salinity changed over time. A barotropic model was developed and calibrated to model tides, discharge division between channels, and salt intrusion. The model findings showed that temporal discharge division can differ significantly from cumulative averages and is influenced by tides and subtidal water levels, especially in the dry season. Discharge variations were found to significantly impact salt intrusion.
DSD-INT 2018 Tidal propagation and salt intrusion in the multi-channel estuarine system of the Mekong Delta, Vietnam - Eslami Arab
1. Faculty of Geosciences
RISE AND FALL:
Tidal propagation and salt intrusion in the multi-
channel estuarine system of the Mekong Delta,
Vietnam
Sepehr Eslami
Maarten van der Vegt
Nguyen Trung Nam
Herman Kernkamp
Arthur van Dam
Piet Hoekstra
13 . Nov . 2018
2. Faculty of Geosciences
CONTENT
• Mekong Delta
• Field Campaign
• D-Flow FM modelling
• Model Findings
• Conclusions
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
3. Faculty of Geosciences
• 40-160Mt/yr of sediment
Milliman & Fransworth (2011),
Kummu et al. (2014),
Nowacki et al. (2015),
Darby et al. (2016),
Vo et al. (2017),
• 300 - 550 billion m3/yr
fresh water
• Seasonality
NW
SE
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
4. Faculty of Geosciences
The Mekong Delta
Coumou & Minderhoud (2016) Minderhoud et. Al. (2017)
• 2,5 million m3/day
groundwater extraction
• 80 million m3/day surface water
extraction (1000 m3/Sec)
Mekong River
Bassac River
Population 22 million
50% of Nation’s Food
• Extensive agriculture &
aquaculture
Subsidence
Water Quality
Erosion
Salt intrusion
Flooding
4m tidal difference
Smagjl et. Al. (2015)
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
6. Faculty of Geosciences
Measurement campaign
Objective:
• Measuring record salt intrusion
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
12. Faculty of Geosciences
What did we learn?
• Salt intrusion responds to:
1. Discharge
2. Tidal variations
3. Subtidal variations
a) Spring-neap cycle
b) Wind-generated surge
13. Faculty of Geosciences
Barotropic Modelling
- 1D rivers and canals
▪ 1400 channels
▪ 4300 profiles
- 54 Movable dams
- Observation points
- 1D & 2D (Vo et al. 2017)
- Water demand
- Offshore boundary
Tidal + subtidal
- Discharge upstream
- Subtidal water level
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
14. Faculty of Geosciences
model calibration
Outline
R&F Proj.
context
Structure
Part-1
Part-2
Part-3
Part-4
Progress
21. Faculty of Geosciences
Tidal propagation
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
22. Faculty of Geosciences
Cumulative Discharge Division
Article
Fraction of main
channel discharge
Dinh An Tran De
Nguyen et al. (2008) 70% 30%
Nowacki et al. (2015) 40% 60%
Xing et al. (2017) 94% 6%
Our Calculation 60% 28%
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
12% demand
24. Faculty of Geosciences
Temporal Discharge Division,
Sensitivity Analysis
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
25. Faculty of Geosciences
• The barotropic D-Flow FM model calibrated in the multi-
channel estuarine system of the Mekong Delta.
• Temporal discharge division can be dramatically different
from cumulative discharge division.
• During the dry season, tidal and subtidal water level play
significant role in discharge division.
• Discharge variations, during the dry season, are
expected to significantly influence salt intrusion.
Summary
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
27. Faculty of Geosciences
, 80km
,180km
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction
28. Faculty of Geosciences
Effect of secondary channels
• The secondary channels
➢ 1% of the total volume
• If we remove the secondary
channels without re-calibration
Mekong Delta
Field campaign
FM modelling
Findings
Conclusions
Introduction