Hanoi is sinking from groundwater withdrawals
Over a third of Earth’s largest aquifers are “stressed,” or being utilized unsustainably based on a 2015 study by researchers at the University of California, Irvine (UCI) using data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites. An aquifer is considered stressed if its withdrawal exceeds its ability to naturally recharge. This gradual loss over time results in what is known as subsidence - as groundwater levels lower, the ground above the land sinks in response. A recent example is California’s San Joaquin Valley, which sunk more than two feet from 2013-2016 due to excessive groundwater withdrawal and irrigation, according to the LA Times. This poses a serious issue for water security because even if recharged, the collapsed aquifer’s capacity is permanently lowered.
In addition to long-term danger to aquifers, subsidence has immediate effects on the human society sitting above. According to Circle of Blue, excessive groundwater withdrawal has caused parts of Hanoi, Vietnam recently to sink more than three feet, requiring apartment buildings to be demolished and rebuilt. With researchers predicting groundwater extraction to increase by as much as 35% in Hanoi within the next three years, the potential for harm to the sinking city only stands to get worse. Circle of Blue points to other “thirsty” cities that have experienced problems from excessive groundwater withdrawal: Shanghai, China, which has experienced approximately $2 billion USD in losses due to subsidence, and Mexico City, which continues to experience sinkholes,
India in particular relies strongly on the Indus and Ganges-Brahmaputra Basins, both of which were considered either “extremely” or “highly” stressed by the 2015 UCI study. This is not surprising, however, given that India is the largest consumer of groundwater worldwide, surpassing both the United States and Canada. The World Bank predicts that if India’s groundwater usage trends continue, in 20 years, 60% of its aquifers will be in critical condition. This is an extremely serious problem for the world’s second-most populous nation of over 1.2 billion people that relies on groundwater for 60% of its agriculture and 85% of its drinking water. In response to these issues, India has set aside 1,445 crore ($224 million USD) under the UN’s Green Climate Fund for the construction of 177 structures to aid in artificial recharge. Many of these structures are recharge wells, or injection wells, for the purposes of artificial recharge (AR). AR wells aid in aquifer recharge by preventing saltwater intrusion and controlling land subsidence, according to the United States EPA. Other structures under the project include dams for fresh water storage and a barrage to divert surface water for irrigation, which together may help to reduce the nation’s dependence on groundwater.
As populations continue to boom in the world’s thirstiest cities and nations, governments must continue to invest in sustainable solutions if we are to keep ourselves, and the ground beneath our feet, from going under.