The Mekong Delta Model: Pioneering Numerical Approaches and Lasting Impacts on Computational Hydrology

In the 21^st century, numerical models are a widespread tool for understanding, visualizing, and simulating hydrological processes, from alpine streams to tropical deltas. A large variety of different models is widely available and offers extensive possibilities for customization to researchers and decision-makers alike. While many challenges remain - such as proper parameterization or data-sparsity in many regions of the globe that renders calibration and validation difficult - numerical models now have a large community of users and the computational infrastructure needed to run them is readily available to most users. 

None of this was the case when the Mekong Delta Model was developed in the early 1960s. Numerical models were in their infancy and few institutions had access to computers. The Mekong Delta Model was a pioneering effort, funded by UNESCO. Its aim was to simulate the impact and assess the viability of a dam across the Tonle Sap river in Cambodia, proposed as part of the plan of the UN’s Economic Commission for Asia and the Far East (ECAFE) to support economic development in Southeast Asia. It was the first computational model built to represent a deltaic area and served not only as a proof of concept, but also as a basis on which many key figures in the numerical modelling community later developed their own work. 

This study seeks to trace the genesis of this groundbreaking model and to explore its impact on the development of computational approaches in hydrology from the 1960s onwards. It is based on an extensive bibliographical survey, archival research in the Archives d’Outre Mer in Aix-en-Provence and the UNESCO archives in Paris, and an in-person interview with a member of the original team at SOGREAH (Société Grenobloise d'Études et d'Applications Hydrauliques), which built the model. The results outline the story of the model, from the contentious tender process in which it prevailed against more established alternative approaches, over the often dangerous data gathering and harmonization stage (set against the background of the Vietnam War), to the influence it had on the community of modellers in places such as the Danish Hydraulic Institute and the University of Colorado.