by O.P. Sabherwal AMIDST the hefty energy crunch, let us not forget the equally pressing water problem. India's water problem is acute and growing - in three directions. In large parts of rural India, as also in many urban localities, water pollution, brackish water and water contamination with chemical effluents are a major cause for disease. Second, there is a growing water shortage in urban areas, especially the big metropolitan centres such as Mumbai, Delhi, Kolkata and Chennai. Third, entire pockets like Saurashtra and Kutch, coastal areas of Tamil Nadu and some landlocked areas of Rajasthan and Madhya Pradesh with scanty rainfall face perennial water scarcity. Add to this the growing population, and the shortage of potable water becomes ever more a serious challenge. A holistic approach is called for to cope with the twin problems of water pollution and fresh water needs of the country in the coming decades. India's nuclear technology comes to the rescue and is already playing a significant role. The good news is that water has become a technology mission for Atomic Energy R&D centres, with BARC in the forefront. Though hardly known, nuclear technology is already cutting into the problem of water management on both aspects - water pollution and augmenting water supplies. Nuclear technology is in action with significant innovation and projects that are grappling with this dual water problem. First the problem of pollution: a major contribution by BARC in this area is development of Reverse Osmosis (RO) technology. Now fully developed and tested, RO technology has been transferred by BARC to a dozen or more competent companies which are already manufacturing and supplying RO units and plants on a large scale, and RO technology has spread country-wide. BARC is actively participating in the Rajiv Gandhi National Drinking Water Mission and has set up a number of reverse osmosis plants in several villages during the last two decades. Another notable contribution in tackling water pollution accruing from BARC's R&D is what is termed "Online Domestic Water Purifier'. This technology too has been fully developed and tested, and has been transferred to several companies for commercial manufacture and countrywide distribution. Next, the challenge of augmenting potable water resources: this requires a national effort. Nuclear technology is already making a significant contribution in this challenging task. Intensive R&D at BARC has focused on developing water desalination technologies, including seawater desalination. This R&D know-how is being harnessed in several projects, paving the way for a chain of desalination projects. Ongoing, a major project for augmenting potable water resources being undertaken by BARC, is the sea water Nuclear Desalination Demonstration Project (NDDP) at Kalpakkam, coupling heat released by the two reactors of the Madras Atomic Power Station into a hybrid - reverse osmosis-cum-multi-stage flash - technologies plant of 6300 cubic metre per day capacity. MSF technology is producing 4500 m3/d quantity and SWRO technology 1800 m3/d. This hybrid technology seawater desalination plant has been in operation for over two years, and its experience could be multiplied at a large number of locations where waste heat could be coupled with water desalination projects to produce potable water. BARC efforts are now being focused on design and development of very large-size MSF-RO hybrid plants for seawater desalination. Enough expertise is available at BARC for this project. Prospects are of putting up a number of large-sized plants of a million gallons a day capacity for brackish and sea-water desalintion and treatment for water reuse. If BARC R&D could be joined with similar work being undertaken by other national institutions, these plans could have a big impact on the acute water situation in the country. In some respects, an even greater contribution, using isotopic nuclear technology in meeting water shortage, is related to the scarce water resources of hilly areas. Now in the process of development, the project harnesses what is known as Isotope Hydrogeochemical Techniques, a nuclear technology, for the recharge of drying springs in mountains. A major breakthrough has been attained in the project to recharge drying springs in mountainous region of Gaucher in Uttarakhand. The Gaucher project is a sort of prototype for similar projects for the recharge of drying springs in mountainous areas elsewhere. In the mountainous region of Uttarakhand, springs are the only available source of water for domestic and agricultural use. Insufficient spring water due to low discharge causes a lot of hardships to the inhabitants there in summer. So, when the Principal Scientific Adviser to the Government of India, Dr R Chidambaram, was requested for help in dealing with the problem of drying springs in the Gaucher mountainous area of Uttarakhand, this prototype project was set in motion. Dr Chidambaram harnessed the BARC Isotope Applications Division for initiating this model project, fully keeping in view its vast potential. Dr Anil Joshi of Himalayan Environmental studies and Conservation also joined force. The project was initiated in December 2003 with first visit of BARC scientists to the Gaucher mountainous area. The project has been intensively researched. The first part consists of identifying the recharge zones related to the respective drying springs in the Gaucher mountainous area. These studies entail mapping out the entire area, locating the sources of spring water, testing the quality of spring water, and the direction of water flow through the mountainous region. It had to be ascertained first as to which catchment area or water body was actually recharging the useful springs or wells within a location. To find out the exact recharge characteristics and relationship between the catchment areas and downstream wells and springs, the isotope hydrology technique was used. Based on the findings, the second part of the project was undertaken, namely, to build up infiltration tanks/check bunds at suitable zones for the collection of rainwater. A catchment area development programme was taken up and structures such as check dams, infiltration wells and contour trenches were constructed to ensure revitalization of the water bodies in higher reaches and also sufficient recharge for the wells and springs downstream. Using the stored water for recharging these drying springs in summer has been a remarkable success - drying springs have been rejuvenated, discharges have gone up by two-three times and new springs have emerged. Based on the success of this project, a replication programme has now been taken up in 10 locations: five in Uttarakhand, three in Himachal Pradesh and two in J&K