The risks Dhaka city runs

It is important to note that in 2011 the mega earthquake that hit the east coast of Japan reactivated dormant faults near Fukushima's nuclear reactor, which caused massive economic and environmental damage to that country. In Oklahoma of the USA a recent hydrocarbon fracking operation reactivated 300 million-year-old dormant faults, which generated more than 3,600 earthquakes and caused moderate damage. This may trigger more devastating earthquakes in future. The faults in Dhaka city and its adjacent areas may be reactivated by earthquakes, induced both by natural and man-made causes, which may result in severe damage to the city.   
EVIDENCES OF MAN-MADE ENVIRONMENTAL DANGERS: The research of  Humane Water (formerly AHWEEC, a US-based non-profit organisation) on Bangladesh's environmental problems has revealed that the overuse of groundwater for municipal water supplies over the last several decades poses a serious threat to the inhabitants of Dhaka city and their properties. The groundwater levels in the Dupi Tila aquifers system have fallen significantly (about 85 per cent of groundwater is extracted yearly by WASA and no information is available about the quantity of water that is being used by several hundred unpermitted and non-regulated private wells). The fall of the water level in the Upper Dupi Tila Aquifer-1 has created a large cone of depression in the entire city. The depth of the declination of the water level varies from 30 metres to 65+ metres, which is equivalent to the height of a building 8-18 stories in height (arrows show the groundwater declination depth).
A cross section of the groundwater level from the Kamarpara/Tongi area to the Bandar area that runs northwest to southwest through the centre of the city gives a clear picture of declination of the groundwater level in Dhaka city. Similar pictures are seen in the east-west and southwest-northeast cross-sections of the city between Mohammadpur to Uttarkhan, Mirpur to Badda, Mohammadpur to Rampura and other areas including Dhanmondi, Gulshan and Banani.
Our team does not have any water level data for the Upper Dupi Tila Aquifer-2. The thickness of the aquifer is 36 metres. The pumping of groundwater from the lower Dupi Tila aquifer has also caused a significant fall in the water level. A groundwater-level cross-section from the National Zoo area to the Fatullah area (northwest to southeast) shows that the groundwater level has declined from 25 to 35 metres. The empty water bearing aquifer layers will gradually shrink due to compaction of the aquifer and excessive pressure from high-rise buildings, overlying sediments and compounding effects of vehicles, industries and other human activities. These processes will generate micro fractures, joints and faults that will extend from subsurface to the surface structures eventually. Over time these micro fractures will cause heavy damage to surface structures. In addition to these issues, tectonic forces such as those generated by earthquakes will cause substantial damage and destruction to the 17 million inhabitants of Dhaka and their properties. Scientific data unquestionably points to the fall in the water level as a contributor to such large-scale destruction. This information is supported by examples and empirical evidence from many other countries that have experienced comparable phenomena.   

The fall in the groundwater level is a serious environmental issue for Dhaka city and other parts of Bangladesh. There is a big difference between the density of the water bearing zone and the dewater zone. The dewater zone once filled with water is now empty and filled with air. The density of air at the sea level is 1.275 Kg/cubic metre and the density of water is 1,000 cubic metres. Therefore, at the sea level the density of air is 784 times less dense than water. Thus, one can comprehend the situation of dewater and water saturated zones of the confined aquifers. The dewater zone has lost its original density completely and has become an unstable zone. The Indian Plate moves at a rate of 4.0 cm/year only, and causes severe destruction through earthquakes. The dewater zones created by pumping of groundwater in the Dupi Tila aquifers are the bright spots for destruction of Dhaka city in a major earthquake. The entire country faces a great risk.  
OTHER CITIES AND AREAS OF BANGLADESH: A significant fall in the water level due to agricultural irrigation, industrial use and municipal water supply for the last several decades has caused arsenic poisoning in groundwater in Bangladesh. Our research findings prove that the arsenic poisoning in groundwater is a recent man-made disaster and that the recent oxidation mechanism is the principle cause of it. The harvest of river water and over-pumping of groundwater have caused a fall in the groundwater level in the entire country. The Dhaka city will face a serious water supply problem in near future. The Dupi Tila aquifer is the principal aquifer system and major source of water supply in the city. It is semi-confined to confined in nature and, as a result, groundwater levels are declining rapidly. The people of Bangladesh must take this problem seriously and should work with the government to resolve the current and future municipal water supply problems in the city without any delay. Many of the natural and man-made environmental problems could be significantly reduced by applying modern geotechnical and seismic hazards investigation, urban environmental geo-engineering planning and engineering technology.
Humane Water  will submit a proposal to the government of Bangladesh for a feasibility study on the following:
1. Sustainable municipal water supply for 30 million people and commercial/industrial use in Dhaka city.
2. Reduction of environmental risk caused by declination of groundwater level.
3. Earthquake risks assessment and prevention measures in Dhaka city.
4. Arsenic-free water supply for drinking, cooking, bathing and gardening purposes.
The government of Bangladesh should immediately take necessary steps to stop installation of deep water wells in the country, develop a policy and permit processes for several hundred non-regulated private wells in Dhaka city and establish water rights of the citizens. Recently, Prime Minister Sheikh Hasina expressed her grave concern about the dewatering groundwater aquifers in Bangladesh. The Prime Minister's efforts to mitigate the environmental disasters the country faces today give the people of Bangladesh a reason to believe that policymakers, scientists and others can achieve sustainable solutions to these issues.
The Prime Minister may consider forming a national team consisting of appropriate policymakers, geologists, geophysicists, scientists, architects, engineers, parliament members of different political parties and mayors to address the national problem. This is a serious issue tied to the very existence of the people of Bangladesh. Like the Prime Minister, the people of all walks of life should be concerned about the natural and man-made environmental hazards the country faces and should seek solutions.
Meer Husain is a professional environmental geologist, founder of Humane Water (Formerly Academy of Healthy Water, Ecosystem and Environment, a non-profit
organisation), Kansas in the USA, and Md Jasim
Uddin is  exploration geologist, Bangladesh.   
 [email protected]