It has been proposed to control the flood which periodically inundates 50,000 sq km in the Lower Basin of the Mékong River in Cambodia and South Vietnam by means of a barrage across the Tonlé Sap. This would transform the Great Lake of Cambodia into a 72 billion cu m reservoir. The used model consist of a system of ordinary first-order differential equations each representing water level as a function of thime in one of the some 300 meshes into which the whole area can be divided. Exchange relations between cells are based either on Saint Venant's dynamic equations or on the weir type exchange laws, inertia terms being ignored in both cases due to the very small velocity of flood propagation. Boundary conditions are represented by about 50 additional imaginary cells. A flood lasting 3.5 months corresponds to about 120 computation cycles with a time increment varying between 6 hrs. and 48 hrs. It requires about 1 hr of computer time. Printout is done by means of the IBM 1401.