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W. Liengcharernsit
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Civil Engineering, Building, Construction & Architecture Engineering Transportation

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DEVELOPMENT OF SEDIMENT TRANSPORT MODEL AND ITS APPLICATION TO SONGKHLA LAKE BASIN S. Yoyrurob; W. Liengcharernsit
Lowland Technology International Vol 13 No 2, Dec (2011)
Publisher : International Association of Lowland Technology

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In the past few decades, rapid population growth in Thailand has resulted in excess utilization of natural resources and degradation of environmental quality. Deforestation in sloping areas for agricultural and residential purposes has resulted in soil erosion from deforested areas with subsequent sediment transport and deposition in receiving water bodies. In order to evaluate the significance of this problem, a mathematical model is developed to simulate sediment transport phenomena in a receiving water body. In model development, total sediment transport is classified as bedload transport and suspended load transport, which result in two interrelated transport models. Threedimensional mass balance equation is used as a basic governing equation for suspended load transport model, whereas two-dimensional mass balance equation is used as a basic governing equation for the bedload transport model. The finite element method is used to solve these governing equations. Since sediment grain size and specific gravity are important factors affecting sediment transport either in the form of bedload or suspended load, the simulation models are developed for each group of sediment grain size and specific gravity, and then the simulated sediment concentrations of various groups are combined to obtain spatial distribution of total sediment concentrations at each time step. The inflow sediment along the boundary of water body is classified into corresponding groups based on their grain size and specific gravity. The developed model is applied to simulate sediment transport pattern in Songkhla Lake which is one of the most important water resources in Southern Thailand.
A LINEAR PROGRAMMIMG MODEL FOR TIDAL RIVER WATER QUALITY MANAGEMENT N. Inyim; W. Liengcharernsit
Lowland Technology International Vol 14 No 2, Dec (2012)
Publisher : International Association of Lowland Technology

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This paper presents the formulation of a mathematical model for tidal river water quality management, considering tidal effect on pollutant transport in a tidal river. The linear programming optimization and finite element method are used in model formulation. The objective function of the model is to maximize total BOD load which can be discharged into the river. The decision variables are the ratio of remaining BOD after treatment to the generated BOD of all controllable sources of BOD load discharging into the tidal river. The BOD and DO constraint inequalities are formulated such that at any time step the BOD values at identified nodal points are not more the specified limits and the DO values are not less than the specifies limits. Since the objective function and all the constraints are linear functions, this optimization problem is in the form of linear programming and the well known Simplex method can be used to solve the problem. To demonstrate the application of the model, it is applied to determine the optimal management plan for allocating the degree of treatment among the central wastewater treatment plants of large municipalities located along the Thachin river in the central region of Thailand. The construction plan includes seven wastewater treatment plants located at different sites along the river. This case study can demonstrate effectiveness of the model in determining the optimal water quality management plan for a tidal river and providing the optimal solution for wastewater management.
DEVELOPMENT OF PHYTOPLANKTON MODEL WITH APPLICATION TO SONGKHLA LAKE, THAILAND S. Suwanidcharoen; W. Liengcharernsit
Lowland Technology International Vol 14 No 2, Dec (2012)
Publisher : International Association of Lowland Technology

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In this study, mathematical models are developed for simulating phytoplankton and nutrients dispersions in a water body. Two-dimensional vertically average mass balance equations of salinity, nitrogen and phosphorus in various forms and phytoplankton nitrogen are used as governing equations. The finite element method with Galerkin’s weighted residual technique is used in model formulation. The developed models are applied to Songkhla Lake, which is one of the most important water resources in the south of Thailand, where algal bloom problem occurs in some months almost every year. Data on nutrient loadings from various sources in the watershed area are estimated based on the existing land use patterns, population density, livestock, aquaculture, and farming activities. Data on water depth and current velocities are obtained from a hydrodynamic model. The results from the model are illustrated to show distribution patterns of salinity, various forms of nitrogen and phosphorus, as well as phytoplankton nitrogen. The developed models can be used as a tool for assessing the effect of nutrient loading on algal bloom phenomena and are useful for water quality management planning of this lake and other water bodies.
Co-Authors N. Inyim S. Suwanidcharoen S. Yoyrurob