Controlled flooding in the Mekong delta

Six years after my last visit to Vietnam I returned to Ho Chi Minh City and the Mekong delta and it was amazing and a real delta adventure! So many things have changed (my former guesthouse is now a lively bar), but also many other things have remained exactly the same (motor bike taxi’s, go-with-the-flow traffic, and the hassle in Ben Thanh Market).

The purpose of the visit was to get an impression of how controlled or facilitated flooding in the Mekong delta takes shape, representing the third case of my PhD project. For that, I travelled together with Tran Duc Dung, who will start his own PhD project soon, to the northern part of the Mekong delta. There are some regions (and a project) where controlled flooding is an inherent part of the agricultural and water system of the delta: notably in An Giang and Dong Thap provinces. Most of the farmers there grow two rice crops per year, and during the flood season a layer of flood water flows overland from Cambodia (and to some extent via the several rivers that make up the Mekong) onto the fields, bringing the required sediments and nutrients in and flushing the water system. It is for that reason that farmers talk about mùa núóc nô, or ‘happy flood’. The slowly raising water levels are kept at bay until August (by the so-called August dikes). Then, the water overflows the dike and floods the area where the second rice crop has just been harvested from.

But (central) governmental policy makers are thinking about growing three rice crops per year, which would necessitate large scale infrastructure to block the overland and controlled floods. Various other actors, from local farmers to representatives from local governments, research institutes and NGO’s are worried about this development and expect increased flood risks in Can Tho (since flood water would not spread out in the north anymore), the largest urban area in the Mekong delta. In addition, preventing sedimentation and nutrient deposition is expected to lead to deteriorated agricultural production, and does not compensate anymore for soil subsidence. It is indeed the balance between facilitating regional ‘good floods’ versus preventing large scale ‘bad floods’ in the delta. These discussions are also taking place within the context of the recently issued Mekong Delta Plan, where Vietnamese and Dutch water experts have aimed to streamline various existing master plans and development trajectories for the delta.

During the first days, Dung and I had some informal discussions with staff from An Giang University. Then we spent a few days by motor bike driving about 250k to visit different districts of An Giang province. In the northwest we visited the flooded forest wetland, which requires a certain flood dynamic (timing and water level) to function as an ecosystem, providing ‘modern nature’ and lots of bird life to the region. On one of the island in the Mekong distributaries the North Vam Nao project proved a very interesting case: the project was designed for full flood control, but after local actors’ engagement, the area now employs rotational flooding in the fields. Also the interviews at the Mekong Delta Development Research Institute, Can Tho, and IUCN, Ho Chi Minh City, were very informative. The movie suggested by Andrew Wyatt (and Ngan Le, who will soon also post on this blog) are very interesting: the disappearance of the flooding season (see also parts 2 and 3).

The coming months I will continue working on this case and later on also plan some short re-visits. If you have ideas, comments or questions (I have lots of additional interesting literature), please let me kow. Thanks to Gerard Pichel for a nice lunch, Dung for sharing our  delta adventure, and Gerardo van Halsema for initial ideas, advices and a nice sea food dinner on the 27^th of Feb!


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