The capital of India may soon have to face the apocalyptic scenario of Zero Day , a term that originated in Cape Town in South Africa where it denotes the situation when the government has to shut off water supply. Delhi and 20 other cities in India are likely to run out of ground water in less than two years, according to a report by Niti Ayog."Supply gaps are causing city dwellers to depend on privately extracted ground water, bringing down local water tables. In fact, by 2020, 21 major cities, including Delhi, Bangalore, and Hyderabad, are expected to reach zero groundwater levels, affecting access for 100 million people," the report says. It says most states have achieved less than 50% of the total score in the augmentation of groundwater resources, highlighting the growing national crisis in which 54% of India’s groundwater wells are declining.The report says that 600 million people in India face high to extreme water stress in the country. "About three-fourth of the households in the country do not have drinking water at their premise. With nearly 70% of water being contaminated, India is placed at 120th amongst 122 countries in the water quality index," it says. NITI Aayog has come out with a Composite Water Management Index as a useful tool to assess and improve the performance in efficient management of water resources. It is the country’s first comprehensive and integrated national dataset for water.In the water index (FY16-17) ranking of non-Himalayan states, Gujarat, Madhya Pradesh and Andhra Pradesh lead with respective scores of 76, 69 and 68. Jharkhand, Haryana and Uttar Pradesh are at the bottom with respective scores of 35, 38 and 38. Among north-eastern and Himalayan states, Tripura leads with a score of 59 followed by Himachal Pradesh at 53. Meghalaya and Uttrakhand have the lowest score at 26.The report says the low performers on the water index are home to nearly 50% of the country’s population, thereby highlighting the significant water risk faced by the country. "The low performers are, worryingly, comprised of the populous northern states of UP, Bihar, Rajasthan, Haryana, and others, and are home to over 600 million people. The poor performance of these states on the Index highlights a significant water management risk for the country going forward. Further, these states also account for 20-30% of India’s agricultural output. Given the combination of rapidly declining groundwater levels and limited policy action (as indicated by the low Index score), this is also likely to be a significant food security risk for the country going forward," says the report.