Worried faces of Dhaka residents with empty water containers in long queues often appear in Bangladeshi news reports. This clearly shows that the city heavily dependent on groundwater is now running towards a water crisis. The invisible resource of groundwater is now becoming visible in policy dialogues on meeting people’s water demand. Since water supply’s future adequacy is being questioned, we have no way left other than addressing groundwater overdraft.
Groundwater: a Precious Resource Beneath Our Feet
Considering vast oceanic water around the globe, our watery planet is mainly saline. Freshwater contains only 3% of the Earth’s water, where groundwater has a 29% share. USGS (United States Geological Survey) defines groundwater as “water that exists underground in saturated zones beneath the land surface” . It is often called a hidden resource since it is not directly visible to us. Being part of the hydrological cycle, groundwater plays a significant role in the continuous water flow among the natural reservoirs. Our daily life is supported by groundwater supply ranging from household work to industrial activities. 50% of the World’s drinking water comes from groundwater resources . According to UNESCO, groundwater is the only source of fulfilling daily basic needs for 2.5 billion people around the World, and it alone contains 43% of all the water used in irrigation . Groundwater also maintains the ecosystem’s health by moderating water level fluctuations and supplying much-needed moisture to the vegetation. While groundwater is regarded as the most precious freshwater source, it is also the most exploited natural resource to date. Research shows that regions under threat of groundwater resources are the abode of nearly 1.7 billion people .
Depletion of Groundwater Scenario in Dhaka City: an Unwanted Bitter Reality
The capital city of Dhaka lies at the heart of Bangladesh. The river Buriganga flows in the south-west part of the town. Dhaka may seem like a town rich in groundwater resources because of its advantageous position in rainfall and river seepage. Ironically, this is not the actual case. Climate change is causing irregular rainfall patterns- torrential rain within a short period and rain deprivation for a long time. This does not help recharge since the overland flow of rainwater happens. Also, the concrete coverage of the city prevents rainwater percolation. The town’s upper formation is a thick clay layer (Madhupur Clay), which contains both horizontal and vertical recharge. So considering the limited recharge capacity, the city is not fit for massive groundwater abstraction. But the shocking fact is that 80% of all the water usage in the town comes from groundwater storage . From 1980 to 2010, Dhaka city experienced a rapid decline in groundwater level . Since 1986, the average rate of groundwater table decline is 2 m per year . The past four decades saw a 50-meter fall of the water table in the city; now, many parts of the city reach groundwater over 60 meters depth .
However, the pattern of groundwater crisis is dissimilar in different parts of the city. Variations of deficit were observed mainly due to population, topographical, and geological environment. In a three decadal study, the highest level of depletion was found in Mirpur, where the groundwater level declined from 8.36 meters in 1980 to 65.97 meters in 2010 . A study of 2015 found the northern part of the city (Uttara, Pallabi, Badda) having a high water level compared to the southern part (Sutrapur, Sabujbagh) as they were not burdened with population pressure and heavy industrialization . The city’s central part (Tejgaon, Motijheel, Ramna) had the highest rate of groundwater withdrawal . Zones near the periphery were found to have a better water level beneath the surface due to the presence of water bodies nearby. Household income often plays a role in water usage. There is a simultaneous increase in per capita income and water usage in Dhaka city .
What is Causing the Drastic Decline?
Experts attribute the increasing density of population and over-extraction of groundwater to the falling water table. Being a hub for social, economic, and cultural activities, the city attracts thousands of migrants around the country. Around 14 million people live in this city of 325 sq. km area . To meet the never-ending demand of this enormous population, the city has undergone large scale groundwater withdrawal. The role of frequent deep tubewell buildup cannot be denied. DWASA (Dhaka Water Supply and Sewerage Authority) kept installing wells to continue the water supply. From 1970 to 2003, the change rate in tube well numbers went beyond 700% . More than 900 private deep tube wells extract a volume in the city, which is probably more than 50% of the withdrawal of the DWASA . Textile industries are also responsible for large scale abstraction . Lack of surface water quality is making people over-reliant on groundwater. Water from rivers surrounding Dhaka is unusable because of excessive pollution, solid waste dumping, and the presence of industrial effluent .
Consequences Reaching Far and Wide
The reckless extraction of groundwater is leading to environmental, social, and economic problems in the city. Experts say the city may experience land-subsidence as the falling water level will no longer support the soil’s sediment structure. Different areas around Dhaka city are subsiding 2 to 16 mm annually due to the groundwater level’s tremendous fall . Existing sources of surface water will be dried up, not being supported by groundwater release. Dried up wells are already causing water scarcity in the capital. The cost of installing and fixing pre-installed wells is getting higher. There is a shortfall of drinking water leading to social instability. If the water level falls below the sea level, there will be a risk of salinity intrusion. Unless steps are taken, the situation can only get worse.
Government Policies and Expert Suggestions to Tackle the Groundwater Crisis
For the efficient management of all types of water resources, the Government of Bangladesh formulated policies from time to time, such as- National Policy for Safe Water Supply and Sanitation (1998), National Water Policy (1999), Water Act (2013), etc. For the most recent one (Water Act, 2013), a noteworthy feature is the license requirement for large-scale extraction beyond household use. The proper application of this depends on ground monitoring; in that case, the authority needs decentralized monitoring approaches and more extensive staff resources . Another challenge in policy implementation is the interaction among different institutional bodies related to water management. There need to be demarcated boundaries of duties so that no conflict occurs between responsible institutions. Also, coordination among agencies should be ensured. Artificial groundwater recharge is possible by installing injection wells. Shifting to surface water for water supply is the need of the time. DWASA has taken initiatives to establish water treatment plants in Pagla, Khilkhet, and Saidabad for the future collection of safe and usable surface water. There can be government incentives for treated water usage and reduced groundwater reliance for factories and industries. Sectoral water allocation can be another effective initiative. Feasibility study and impact assessment should be practiced more both by the government and the private sector. Building general awareness is fundamental since people do not value groundwater as a resource.
We need access to safe, uncontaminated water, but that should not come from vanishing an invaluable resource with a little chance of replenishment. Both policymakers and water users must focus their attention on groundwater resources before over-exploitation of it results in environmental, economic, and social catastrophe.
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Department of Geography and Environment, University of Dhaka.