Numerical modelling of flow dynamics in the Tonle Sap by means of a discontinuous Galerkin finite-element model

Le, Hoang Anh [UCL] Lambrechts, Jonathan [UCL] Deleersnijder, Eric [UCL] Soares Frazao, Sandra [UCL] Gratiot, Nicolas Ortleb, Sigrun

The Tonle Sap lake, located in the Cambodian floodplain of the Mekong River system, plays an important role for freshwater storage in Cambodia and the Vietnam Mekong Delta. The lake’s water level can rise by approximately 10 m and its water volume can increase 5 times during a year, showing various drying and wetting areas in the lake and its floodplains. Thus the accurate simulation of wetting - drying processes in this domain is essential for water management in the Mekong River system. Here, we present the extension of an existing wetting - drying algorithm in two space dimensions. The algorithm consists in applying a threshold value of fluid depth for a thin layer and a blending parameter in order to guarantee positive values of the water depth, while preserving local mass conservation and the well-balanced property at wet/dry interfaces. It is implemented in SLIM (Second-generation Louvain-la-Neuve Ice-ocean Model, www. slim-ocean.be), a discontinuous Galerkin finite element model (DG-FEM) solving the shallow water equations in a fully implicit way. Before applying in the Tonle Sap lake, the technique is validated against the standard analytical test cases (Balzano 1, Balzano 3 and Thacker).