5:15 PM - 6:30 PM
[AHW21-P06] Development of a numerical model to simulate the salinity distribution in the tidal area of the lower Chao Phraya Basin, Thailand
The purpose of this study is to clarify the actual situation of saltwater intrusion in the lower Chao Phraya River in Thailand. In coastal flatlands, sea level rise due to climate change causes an increase in the extent of saltwater intrusion. As a result, there is a risk of tap water intake failure in areas where brackish area in river is used as water intake source.
Thailand has large seasonal variations in river flows due to its tropical monsoon climate. 75% of BMA tap water is taken from Chao Phraya River. The intake plant is located in a brackish area 95.1 km upstream from the river mouth, and is affected by water intake failure when the river flow is low. In this study, a numerical model was developed to estimate the salinity distribution in the lower Chao Phraya River in Thailand.
This study used a three-dimensional environmental hydrodynamic model, Fantom, which is based on a k-ε turbulence model. The structure of the longitudinal section was the riverbed elevation surveyed by the ultrasonic sounding (DT-X). The structure in the cross section was a constant upstream river width. The used data were the flow velocity observed by the acoustic Doppler current profiler(ADCP), the periodical water quality analysis data and the monitoring data of water quality observed by MWA. The boundary condition at the upstream end was the discharge (m³/s) of Chao Phraya dam, 287.4 km upstream from the river mouth, and the boundary condition for water quality was 0.1 (‰) of the lowest observed salinity. The boundary condition at the downstream end was the water level (m MSL.) at the river mouth and the boundary condition for water quality was 30 (‰) of the average salinity of the Thailand Bay. The meteorological conditions were the hourly wind speed (m/s), temperature (°C), relative humidity (‰), pressure (Pa), and rainfall (mm) at Bang Na, where a station of the Meteorological Department of Thailand is located.
As the result of the simulation, the peak salinity at the intake plant in the dry season and the fluid mixing near the bottom layer could be modeled. However, the study has not been able to simulate the peak salinity timing and quantitatively.
The numerical model in this study was able to model the qualitative seasonal variation of salinity. In the future, it is necessary to analyze the risk of water intake using the experimental results of climate change.
Thailand has large seasonal variations in river flows due to its tropical monsoon climate. 75% of BMA tap water is taken from Chao Phraya River. The intake plant is located in a brackish area 95.1 km upstream from the river mouth, and is affected by water intake failure when the river flow is low. In this study, a numerical model was developed to estimate the salinity distribution in the lower Chao Phraya River in Thailand.
This study used a three-dimensional environmental hydrodynamic model, Fantom, which is based on a k-ε turbulence model. The structure of the longitudinal section was the riverbed elevation surveyed by the ultrasonic sounding (DT-X). The structure in the cross section was a constant upstream river width. The used data were the flow velocity observed by the acoustic Doppler current profiler(ADCP), the periodical water quality analysis data and the monitoring data of water quality observed by MWA. The boundary condition at the upstream end was the discharge (m³/s) of Chao Phraya dam, 287.4 km upstream from the river mouth, and the boundary condition for water quality was 0.1 (‰) of the lowest observed salinity. The boundary condition at the downstream end was the water level (m MSL.) at the river mouth and the boundary condition for water quality was 30 (‰) of the average salinity of the Thailand Bay. The meteorological conditions were the hourly wind speed (m/s), temperature (°C), relative humidity (‰), pressure (Pa), and rainfall (mm) at Bang Na, where a station of the Meteorological Department of Thailand is located.
As the result of the simulation, the peak salinity at the intake plant in the dry season and the fluid mixing near the bottom layer could be modeled. However, the study has not been able to simulate the peak salinity timing and quantitatively.
The numerical model in this study was able to model the qualitative seasonal variation of salinity. In the future, it is necessary to analyze the risk of water intake using the experimental results of climate change.