While the country is in the throes of the \u201cworst water crisis in its history\u201d, water-scarce states are more efficient than others in managing the resource. According to a Composite Water Management Index developed by NITI Aayog, Gujarat topped among states in efficiency of water management in 2016-17, followed by Madhya Pradesh, Andhra Pradesh, Karnataka and Maharashtra. However, among the \u201clow performers\u201d are the populous northern states including Uttar Pradesh, Bihar and Rajasthan, which are home to over 600 million people or 50% of the country's population. \u201cThese (low-performer) states also account for 20-30% of India\u2019s agricultural output. Given the combination of rapidly declining groundwater levels and limited policy action, this is also likely to be a significant food security risk for the country going forward,\u201d the think tank said. The water index scores for FY17 vary from 76 (Gujarat) to 26 (Meghalaya), with the median score being about 49 for non-Himalayan states and about 31 for others. Worryingly, 60% of states (14 out of 24) have achieved scores below 50 and have been classified as low performers. By 2030, the country\u2019s water demand is projected to be twice the current available supply, implying severe water scarcity for hundreds of millions of people and an eventual ~6% loss in the country\u2019s GDP, it said. Among northeastern and Himalayan states, Tripura has been adjudged No. 1 in effective water management in FY17 followed by Himachal Pradesh, Sikkim and Assam. In terms of incremental change in index (over the FY16 base), Rajasthan was the top performer among non-Himalayan states and Tripura among the other states. The index comprises nine broad sectors with 28 different indicators covering various aspects of groundwater, restoration of water bodies, irrigation, farm practices, drinking water, policy and governance. With data collected from multiple national and state stakeholders and a robust third-party data validation process, it has FY16 as the base year. It is reckoned that the index would be useful annual tool to assess and improve the performance in efficient management of water resources. As per the report of National Commission for Integrated Water Resource Development, the water requirement by 2050 in high use scenario is likely to be 1,180 billion cubic metres (bcm) in India, whereas the present-day availability is 695 bcm. The total availability of water possible in country is still lower than this projected demand, at 1,137 bcm, NITI Aayog said.