Le modèle mathématique du Delta du Mékong

A mathematical model of the Mekong delta

¹ Professeur à l'Université de Bologne, ancien directeur de la Division des études, de la recherche et de l'enseignement technique de l'Organisation des Nations Unies pour l'Education, la Science et la Culture (UNESCO) et directeur du projet du modèle mathématique du Delta du Mékong.
² Chef adjoint du Service hydroélectrique à la Société Grenobloise d'Etudes et d'Applications Hydrauliques (SOGREAH) de Grenoble et ingénieur en chef du projet du modèle mathématique du Delta du Mékong.

Résumé

1st PART 1. The problem. The Mekong runs through several countries, governing both their economic development and human living conditions. Thanks to the availability of powerful modern facilities and such important international liaison organizations as UNESCO's Mekong Committee, development of the Mekong could be visualised in terms of major polyvalent development units concerning many of the riparian countries. One of the first such units is the Tonle Sap dam. Under present conditions, when the Mekong flood reaches the capital of Cambodia, Phnom Penh, it fills up the gigantic natural reservoir of the Grand Lac through the Tonle Sap river, and when the flood recedes, the Grand Lac drains back into the Mekong by the same way. This quite appreciable regulating effect, however, cannot cope with floods rising or falling excessively fast, rising too high or not falling low enough; in order to remedy this shortcoming, it is planned to build a dam on the river Tonle Sap linking the Grand Lac and the Mekong, which will control the filling and emptying of the Grand Lac. Before embarking upon the construction of such a dam, however, it was considered vital to determine and provide a numerical illustration of its effects on various factors governing hydraulic conditions in the Delta. 2. The mathematical model. A mathematical model was necessary to investigate the hydraulic effects of the dam, with the following requirements: (i) That is should he able to represent natural flood propagation in the Delta; (ii) That it should feature the dam; (iii) That it should enable comparison of results with and without the dam. It was decided to use a mathematical model for this hydraulic investigation because of the very large area to be featured (50,000 sq.kms) and the tremendous range of the natural phenomena involved (velocities varying between a few millimetres/sec. and 2.5 metres/sec., depths from a few decimetres up to thirty metres or so, tide structures varying with shore position, etc.). The study was financed by the United Nations Special Fund and the riparian countries, managed by UNESCO, and carried out by Société Grenobloise d'Etudes et d'Applications Hydrauliques (SOGREAH). It covers the Mekong Delta and concerns two countries: Cambodia and Vietnam.