Right on the edge of the Ganga basin that spans 11 Indian states lies Naujhil block, a few kilometres west of Yamuna in UP's Mathura district. You would think this is a blessed location with plentiful water all round.With its 17 tributaries, including the Yamuna, Ganga's catchment area has about 525 billion cubic metres (bcm) of surface water and about 171 bcm of groundwater On average, it receives a million cubic metres of rainfall on every square kilometre. But Naujhil block is a declared “dark zone“, that is, its groundwater extraction far exceeds the recharging rate and use of electricity for pumping water is not permitted.Because of heavy withdrawal, the groundwater is very saline now.Subhash Nauwar , a farmer from Managarhi village in the area, says, “About 35-40 years ago, there was no problem. This is the khadar (floodplain) of the Yamuna and its water would recharge the groundwater sources. But people wanted more crops, so a bund was built to prevent flooding. Now there is no water.“It's bizarre. Most residents of Managarhi use bottled water for drinking and cooking, as if they were living in a desert and not in one of the world's most water-rich plains.This water scarcity is spreading across India, smothering idyllic villages and high-rise city habitats in equal measure. No Indian city supplies 24x7 drinkable water to all of its residents. In many cities, including Bengaluru and Chennai, water scarcity has reached crisis levels and in pampered Delhi, every summer brings intense water scarcity for the disadvantaged sections. Meanwhile, in rural India, zooming agricultural production over the years has mostly been fuelled by heavy use of groundwater because not enough investment was made for using surface and rainwater through canals and reservoirs.Now, take a look at India's water equation: after accounting for losses due to evaporation and unusable water like brackish water or swamp water, the total usable water available in the country is 1,123 bcm, while the total water consumption in 2006 was 829 bcm, projected to rise to 1,093 bcm by 2020. So, in just a few years, India will reach its limit of water consumption because water supply cannot be increased. It is a definite, finite resource.Increase in population has, of course, contributed to the situation reaching these dire straits, but a closer look will reveal gross mismanagement and neglect by governments, coupled with an unbridled destruction of resources as if there is no tomorrow.Take rainwater for instance. Just 18% of rainwater is used effectively while 48% enters the river systems, most of which just flows into the ocean, according to Narayan Hegde , a water expert with the BAIF Research Development Foundation.“Farm ponds, percolation tanks, water reservoirs and small and medium-sized dams can help retain more sur face water while increasing the groundwater recharge,“ he told TOI.This would ease some of the pressure off groundwater usage that has pushed 29% of the country's blocks into the “over-exploited“ category , that is, where groundwater withdrawal is more than the possible recharge. This indiscriminate withdrawal, as in Naujhil, has led India to showing an annual groundwater usage that is more than the combined usage by the US and China. Studies by Nasa using satellite imagery show that the Indus basin, which includes the high food producing states of Punjab and Haryana, is one of the most stressed aquifers in the world. If the current trends continue, by 2030 nearly 60% of Indian aquifers will be in a critical condition.This means that some 25% of the agricultural production will be at risk -a devastating scenario.India's cities are teetering on the brink of an unimaginable water crisis because of unplanned growth and low priority to provision of safe drinking water. Loss due to leaks in the supply systems and wasteful consumption practices pose a serious and untackled problem. Cities also symbolise the injustice of water distribution with well-heeled localities getting as much as 6-8 times more water than the poorer localities.Here, too, rainwater harvesting can play an important role in supplementing municipal supplies and taking the load off precious groundwater resources.Take the example of Delhi. It receives a mindboggling 690 billion litres of rainfall every year. Harvesting even 25% of this would yield 172 billion litres. With an average demand of about 5 billion litres per day , this could just be sufficient to tide over a hot, waterless summer month.A mix of traditional and modern technologies needs to be urgently put in place to tackle India's impending water crisis, argues Hegde. This includes watershed development programmes, increasing the efficiency of irrigation by replacing the prevalent flood irrigation with drip or sprinkler systems and creation of desalination plants to convert seawater into drinkable sweet water.