Development of a two‐dimensional finite element model for inundation processes in the Tonle Sap and its environs

Abstract

A hydrodynamic model, which covers the floodplains of the Mekong River from Kratie in Cambodia to near the Vietnamese border, was developed using a finite element method (FEM) with 2D shallow-water equations. The model was applied to typical flows of recent largest (2000) and smallest (2003) flood years. Main roads, dikes, colmatages, and road-opening works in the study area, which may influence flow regimes, were introduced into the simulation. Moving boundary problems were accommodated by applying a threshold technique in which nodes having a thin water depth were reset to dry ones in all moving boundary elements at every time increment. Simulated results and available observed water levels and discharges were compared to validate the model. The simulated results produced a lot of hydrologic data for the basin areas, without gauging, and these data can be used to evaluate the effects of basin management on flooding and agricultural water use.

Water balance analysis for the Tonle Sap Lake–floodplain system

“…Second, only rather recently have hydrodynamic models of the system been developed with an order of accuracy and detail sufficient to provide the required insights on, for example, the overland flow from the Mekong mainstream to the lake's floodplain (e.g. Fuji et al, 2003;MRCS/WUP-FIN, 2003;MRCS/WUP-FIN, 2007;Hai et al, 2008;Västilä et al, 2010).…”

An implicit wetting–drying algorithm for the discontinuous Galerkin method: application to the Tonle Sap, Mekong River Basin

“…Thus the flow changes its direction and water discharges from the Tonle Sap lake towards the Mekong River. Hydrologically, the lake functions as a regulatory reservoir for the Mekong Delta of Vietnam [36,40], storing approximately 50 % of total Mekong inflow and releasing 90 % of outflow to the Mekong River [41], providing a freshwater inflow to the downstream region in dry season [42]. With this phenomenon, the flooded area varies from 7,190 to 12,720 km 2 [34] and causes the occurrence of dry areas after water recedes.…”

An Integrated Hydrological-Hydraulic Model for Simulating Surface Water Flows of a Shallow Lake Surrounded by Large Floodplains

“…On the boundary conditions, the upstream inflow discharge from tributary rivers to the lake was given by the simulated results of GBHM. The water level at the mouth of the Tonle Sap River (yellow points in Figure 2) simulated from MIKE 11 was set as the lower boundary condition, so that the backwater effect observed in the rainy season [41] is reasonably taken into account. This nesting system from hydrological modelling and 1-D hydraulic modelling to 2-D hydraulic modelling turns out to realize accurate lake flow simulation.…”

“…This distinctive ecosystem is being maintained and characterized largely by the adjacent huge floodplains and district seasonality [37][38][39]. Many researchers [24,[40][41][42][43] have thus investigated hydrological characteristics of TSL. Yet, the modelling of its inundation pattern and surface water dynamics have gained less attention.…”

“…Given the hydrological and ecological importance of floodplains, however, it is critically important to develop a feasible modelling approach to describe such a dynamic inundation pattern for enhancing our scientific understanding as well as environmental management. For this purpose, sophisticated finite volume methods have been utilized [41] but numerically efficient schemes such as the LIEs have not been examined so far.…”