Researchers report increasing dependence on groundwater after frequent droughts as the cause for the alarming decrease in groundwater levels
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Researchers from IIT Bombay report increasing dependence on groundwater after frequent droughts as the cause for the alarming decrease in groundwater levels in South India.
Last year, in June 2019, the people of Chennai were forced to deal with an alarming fact — the water in the city’s reservoirs had dropped to 0.1% of their capacity. Now, the sight of frenzied water trucks, empty buckets, and agitated citizens has become increasingly common in India, especially in the south. A 2019 report from the National Institute of Transforming India (NITI) Aayog, the Government of India, claimed that 21 Indian cities, including Bangalore, Delhi, Vellore, Chennai, and Hyderabad, will run out of groundwater by 2020. What is causing this crisis, and why is the South being affected disproportionately? Researchers Akhilesh S Nair and Prof J Indu from the Department of Civil Engineering at the Indian Institute of Technology Bombay (IIT Bombay) offer an explanation to these questions in a recent study, where they stress the repercussion of frequent droughts. The study was published in the International Journal of Remote Sensing.
The researchers analysed the groundwater data retrieved from the Gravity Recovery and Climate Experiment (GRACE) satellite of NASA as well as from a collection of about 6000 wells that are monitored by the Central Ground Water Board (CGWB) for a period of 13 years (2003–2016). They observed that most of the periods that saw significant changes in groundwater levels were from 2009, and hence, split their analysis into two segments: pre-2009 and post-2009. The researchers found that, in the south, groundwater levels were increasing pre-2009 and decreasing at an extremely alarming rate of 0.25 centimetres per month post-2009. In 2009, India experienced one of the worst droughts due to insufficient rainfall, which was 23% below the average annual levels. Moreover, the unfavourable geology of South India consisting of hard rocks such as granite and basalt, which does not allow rainwater to seep easily, adversely affected the depleting groundwater levels.
After 2009, the fluctuating rainfall levels had a prominent effect on groundwater storage. Further, expansion of major cities like Chennai, which saw infrastructure being constructed over water reservoirs, has weakened the groundwater recharge process. These human-made obstructions hamper the seepage of water into the ground, leading to floods and contamination of groundwater with harmful microbes and chemicals. (Source: Edited from IIT Bombay Research Highlights written by Balaram Vishnu Subramani)