The Phantom Menace in Yangon: Land Subsidence
Whenever most of the citizens in Yangon, especially those who live in an apartment, experience water shortage in their neighborhood, extracting groundwater is the first solution that comes to their minds. Of course, we know that water supply in Yangon is still inadequate to some parts of Yangon. That is why we still try to find out how to solve this issue. In general, people try to resolve this problem by means of extraction of groundwater. Groundwater extraction is a very simple and commonly used solution. Gradually though, this solution might become the phantom menace for upcoming mega city, Yangon.
In 2017, it was a graduate student of Delft University of Technology, Teije van der Horst, who undertook to research this issue. He used two different satellites to show land subsidence in Yangon. He formulated his master thesis "Sinking Yangon" in one and a half year. To assess if subsidence is occurring, surface deformation measurements were performed using Synthetic Aperture Radar interferometry (InSAR) with data from the recently launched Sentinel-1, revealing that parts of the city are subsiding at rates over 9cm per year. Through mapping water extractions onto the townships of Yangon, extraction rates up to 9mm per year were found. Though a relation between surface deformation and groundwater extraction is not established in this thesis, a recommendation is given to alleviate negative effects caused by ground water pumping.
From the perspective of water resources management, it would be wise to act on the possibility that the surface deformation is being caused by groundwater extraction. Although they are not always immediately visible, the damages resulting from them can be significant. Moreover, many of the subsidence effects are technically non-reversible.
During his stay in Yangon Teije did groundwater extraction analysis. He found that very limited quantitative data was available – and of sufﬁcient quality - to perform an accurate analysis. Many of the used data sources were unavailable at a smaller scale than at township level and some were inconsistent or incomplete. For the YCDC tube well dataset, half of the wells were not geo-referenced. Another limitation within this dataset was that only the capacity for each tube well was listed rather than actual extraction amounts.
Seeing is believing
Near the end of this research, some visuals were collected in one of the townships, Dagon Myothit (South) showing signiﬁcant subsidence and were georeferenced using a GPS application. Though these pictures do not prove the existence of subsidence, they do show signs of deterioration. Teije remarks that there are an incredible number of recently constructed high-rise buildings and that many constructions are still ongoing.
Counter-claim on the side of urban dwellers
From the perspective of Yangon citizens, as mentioned above, groundwater extraction is currently the only way water scarcity is solved. This is also a knowledge issue. There should be more education and awareness to make sure that groundwater extraction is legitimate and sustainable. We should be able to expand our water resources management knowledge though many attempts are made to signiﬁcantly reduce the amount of water extracted from the subsoil. Unfortunately, it might still take many years to get every citizen connected to other means of water supply.
The full thesis can be found at: https://www.myanmarwaterportal.com/repository/281-sinking-yangon.html
Teije van der Horst is now working at Van der Sat as a water remote sensing analyst.