According to U.N.E.P Global 2000 Report, if present trend continue, by 2025, 2/3 of the world's population will live in water stressed areas.
With 40% of the worlds food supply being grown on 17% of the cropland that is irrigated, there the need for irrigation is unquestionable. In many countries sources are already over-allocated.
The Nile, the Ganges, the Indus, the Colorado, and many other rivers have been diverted so that at some time during the year they do not reach the ocean.
The situation is even worse with ground water supplies. As the water table falls, the cost of deepening wells and pumping becomes prohibitive, and land is taken out of production. Since the peak in 1978, the amount of land irrigated by the aquifer has fallen by 20% with a predicted drop of another 20% by 2020.
With water deficits estimated to be 200 billion cubic meters per year globally, it is clear that either a significant amount of land will come out of production, or will be switched from grain crops to less water thirsty crops. At a normal ratio of 1000 tons of water to one ton of grain this implies that up to 10% of the world's grain harvest is being produced with deficit water. So not only do we need to find a source for water to increase the production of food for the growing population, but we need to replace the water that is already being consumed at an unsustainable rate.:
