This is a comment of an independent expert on Mekong Delta ecology, Nguyễn Hữu Thiện, in a workshop organized on 26 November. The event was with the framework of the project “Governance of Land Subsidence and Groundwater Management for the Mekong Delta”, which is funded by the Government of the Netherland through the Embassy of the Netherland in Vietnam and cooperated with the Ministry of Natural Resources and Environment (MONRE). The project is implemented in four provinces of Bến Tre, Cần Thơ, Sóc Trăng, Kiên Giang.
According to Thiện, land subsidence is a critical issue in the Mekong Delta. He mentioned data from MONRE showing that the average land subsidence in this region is 1 cm/year. In some areas, it is up to 5.7 cm/year, while the sea level rise is 3 – 5 mm/year. Cần Thơ is the hotspot of land subsidence with a sinking rate of over 5 cm/year between 2015 – 2019 (Interferometric Synthetic Aperture Radar (InSAR)´s data). Between 2005 – 2017, the rate was 4.37 cm/year (MONRE’s data). Sóc Trăng is also facing land subsidence at a rapid rate of 4.4 cm/year between 2005 – 2017 (MONRE´s data) and 5 – 6 cm/year between 2015 – 2019 (InSAR´s data).
The land sinking has resulted in other challenges including growing saline intrusion in both surface and underground water. The risk of submerging under the seawater can be predicted for some areas by 2050 depending on the rate of sea-level rise.
Thiện referred to two major reasons for the large-scale land subsidence in Mekong Delta at the regional level are the natural compression process and overexploitation of underground water. To avoid large-scale damage, the exploitation of groundwater must be restricted to a sustainable level. There is already an existing Decree 167/2018/ND-CP on the restriction of underground water exploitation to control saline intrusion and land subsidence. It is implemented by determining and publicizing restriction areas, where regulations on exploitation restrictions corresponding with the identified problems of those areas are applied. However, the implementation of this Decree is challenging because of lack of data, spatial planning, and proper monitoring network; lack of financial and technical capacities, and limited regional coordination, etc. For example, data on subsidence and groundwater extraction are only available at the regional level, not at the provincial level. Therefore, it is difficult to develop complete maps on restriction zones. Thiện also recommended that there should be a master plan on groundwater for Mekong Dela. Besides, it needs to promote coordination in the region and a mechanism for information sharing. Finally, Decree 167 should integrate with other policies and supplement sanctions to handle violated cases.
Sources & further information: “Chia sẻ thông tin quản trị sụt lún đất và quản lý nước ngầm tại ĐBSCL” at https://www.vietnamplus.vn and “Low-lying Mekong Delta deals with worsening land subsidence” at https://vietnamnews.vn, accessed on 29 November 2021.