As we find water resources becoming increasingly scarce, there is, without a doubt, a need to conserve water resources like other valuable resources that we are now slowly learning to conserve and use better. Once again, here, a major failure as far as South Asia and particularly India is concerned, shows up: Hydroponic cultivation of vegetables, something that works very effectively for vegetables like tomatoes for example, was something that was actively experimented with by British scientist James Sholto Douglas in India in what came to be known as the "Bengal System" of agriculture. I have no idea how many tomatoes or any other vegetable are hydroponically grown in India but the percentage cannot be very high.
Hydroponics is basically a method of growing vegetables in a nutrient solution and without soil in tanks either built for the purpose or adapted from other use like old car batteries etc. There is some rough aggregate, usually gravel laid out at the bottom of the tank for the plant's roots to hold on to. The system is considered environmentally friendly because it reduces the possibility of soil borne diseases in plants as there is no soil used. Also, in conventional agriculture, water that is poured into the soil to water plants gets wasted to a greater extent than the water that is stored in tanks for hydroponics. Finally, better utilization is made of the nutrient fertilizer as some of it cannot leach away into the soil as can happen in conventional agriculture.
There are several websites dedicated to hydroponics as a hobby and someone who is interested could grow vegetables for home consumption on a domestic terrace if they wished to. Some websites taken from the net at random include: http://www.hydroponicsonline.com/ and http://www.ext.vt.edu/pubs/envirohort/426-084/426-084.html There are also somewhat more advanced sites like http://ag.arizona.edu/PLS/faculty/MERLE.html this one which discusses the early failures and problems with hydroponics and the current successful methods of using hydroponic cultivation.
For those who want to try this out, please check the following links: http://www.growingedge.com/basics/start.html and http://www.simplyhydro.com/whatis.htm In any case, a Google search should throw up tens of thousands of websites on hydroponics as well as communities from which information could be received.
Hydroponics will NEVER replace conventional agriculture because grain crops, the most important ones as far as food is concerned, cannot be grown hydroponically. But in parts of the world like S0uth Asia where as many as 7 in 10 people traditionally work in agriculture, there is a strong possibility of maximizing efficiency in the use of water by training more people in the use of hydroponic techniques especially in growing vegetables.
As a final note, I buy hydroponically grown tomatoes at DOminicks and Jewel-Osco whenever they are available. Those who know me know how finicky I am as far as taste is concerned. I have never found any problem with taste or texture in hydroponically grown tomatoes. Their considerably lower cost does not hurt either!