Introduction

Over 20 million Vietnamese and Cambodian people live in the Mekong floodplains, which includes the Vietnam Mekong Delta and parts of the Cambodian Lowlands. This region has recently been dubbed as a "biological treasure trove" as the floodplains are home to many species of birds, fish and mammals. It is also a very productive agricultural area.  Apart from the Tonle Sap floodplain, around 72% of the floodplains belongs to Vietnam, of which 2.6 million ha are used for agriculture, (one fourth of Vietnam's total agricultural land). This region provides up to 52% of rice and 70% of fruit production in Vietnam. In addition, the Mekong Delta is Vietnam's most important fishing region. It has almost half of Vietnam's capacity of offshore fishing vessels. The rest of the delta in Cambodia is also the most agriculturally productive region in that nation. The high bio-diversity and agricultural productivity of the Mekong Delta can be attributed to its stable hydrological regime and rich sediment flows provided by the Mekong River.

The Mekong River, however, is changing, and the Mekong floodplains is now facing several problems:

1. The construction of multiple dams in the upper part of the Mekong Basin may alter the natural hydrology in the Delta and also potentially result in sediment changes due to excess sediment trapping by upstream dams
2. The construction of delta-based water infrastructure for flood prevention and irrigation may change flooding and sediment distributions in the Delta
3. Being a low-lying coastal region, the region is particularly susceptible to floods resulting from sea level rise due to climate change.

Objectives

The main aim of this project is to understand to what extent the above problems will alter the hydrology and sedimentation in the Mekong Delta.

The project involves 3 steps:

1. Quantify historical and recent alterations and identify the likely sources of those alterations (climatic changes or human interventions in the Vietnamese delta or upstream).
2. Understand the impact of future water infrastructure development and climate change on hydrologic regimes in the delta through hydrologic and hydrodynamic modelling.
3. Understand the impact of future water infrastructure development and climate change on sedimentation in the delta and the subsequent effect of sediment changes on rice cultivation in the delta.

Contrast between flood protected areas (bottom of picture) and un-protected areas (top of picture) in the Long Xuyen Quadrangle region of the Vietnam Mekong Delta during the peak flood season of 2014

Related presentations and publications

Dang, D.T., Cochrane, T.A., Arias, M.E., Van, P.D.T. 2018. Future hydrological alterations in the Mekong Delta under the impact of water resources development, land subsidence and sea level rise. Journal of Hydrology: Regional Studies, 15: 119 - 133.

Dang, D.T., Cochrane, T.A. 2016. Hydrological modifications in the Mekong floodplains from development and climate change. The Water Infrastructure and Environment Conference, Queenstown, New Zealand, 28 Nov – 2 Dec (Poster).

Dang, T.D., Cochrane, T.A. 2016. Quantifying sediment dynamics at the Bassac, Tonle Sap and Mekong river confluence at Chaktomuk, Cambodia, using remote sensing. Proceedings of the Vietnam-Japan Workshop on Estuaries, Coasts and Rivers 2016, Ho Chi Minh City, Vietnam, 20 – 21 Sep: 162-173.

Dang, D.T., Cochrane, T.A, Arias, M.E., Van, P.D.T., de Vries, T.T. 2016.Hydrological alterations from water infrastructure development in the Mekong floodplains. Hydrological processes, 30: 3824 - 3838.

Dang, T.D., Cochrane, T.A. 2016. Determining the main drivers of future hydrological alterations in the Mekong floodplains. Waterways Postgraduate Student Conference, Lincoln, New Zealand, 15 Nov. 

Dang, D.T., Cochrane, T.A., de Vries, T.T., Arias, M.E., Van, P.D.T. 2015. Remote sensing and spatial interpolation as a proxy to study sediment distribution in the Mekong Delta, Vietnam. NZ Geospatial Research Conference, Christchurch, New Zealand, 7 – 9 December (Poster).

Dang, D.T., Cochrane, T.A., de Vries, T.T., Arias, M.E., Van, P.D.T. 2015. Flood regime changes in the Mekong River floodplains as impacted by future hydropower development. Waterways PG Research Conference, New Zealand, 17 Nov (Poster).

Dang, D.T., Cochrane, T.A., Arias, M.E., Van, P.D.T., de Vries, T.T. 2015. Analysis of water level changes in the Mekong Floodplain impacted by flood prevention systems and upstream dams. E-Proceeding of the 36^th IAHR World Congress, the Hague, the Netherlands, 28 June – 3 July 2015. 

Dang, D.T., Cochrane, T.A, Arias, M.E., de Vries, T.T., Van, P.D.T. 2014. Hydrologic changes in the Mekong River Floodplain as impacted by upstream hydropower and flood prevention system development. Waterways PG Research Conference, Lincoln, New Zealand, 18 Nov (Abstract and presentation).