By Tina Casey •
May 19, 2009
Mom always said to take your vitamins, and now it looks like she was right. A good dose of vitamin B12 could be the key to cleaning up thousands of sites contaminated by solvents, particularly industrial degreasers and dry cleaning chemicals known as trichloroethylene (TCE) and tetrachloroethylene (perc). These are two of the most common ground contaminants in the U.S., and when they get into aquifers, they are among the most difficult to remediate. All that may be about to change.
By Lester R. Brown
With water shortages emerging as a constraint on food production growth, the world needs an effort to raise water productivity similar to the one that nearly tripled land productivity during the last half of the twentieth century. Worldwide, average irrigation water productivity is now roughly 1 kilogram of grain per ton of water used. Since it takes 1,000 tons of water to produce 1 ton of grain, it is not surprising that 70 percent of world water use is devoted to irrigation. Thus, raising irrigation efficiency is central to raising water productivity overall.
In surface water projects—that is, dams that deliver water to farmers through a network of canals—crop usage of irrigation water never reaches 100 percent simply because some irrigation water evaporates, some percolates downward, and some runs off. Water policy analysts Sandra Postel and Amy Vickers found that “surface water irrigation efficiency ranges between 25 and 40 percent in India, Mexico, Pakistan, the Philippines, and Thailand; between 40 and 45 percent in Malaysia and Morocco; and between 50 and 60 percent in Israel, Japan, and Taiwan.” Irrigation water efficiency is affected not only by the type and condition of irrigation systems but also by soil type, temperature, and humidity. In hot arid regions, the evaporation of irrigation water is far higher than in cooler humid regions.
In 2004, China’s Minister of Water Resources Wang Shucheng outlined for me plans to raise China’s irrigation efficiency from 43 percent in 2000 to 51 percent in 2010 and then to 55 percent in 2030. The steps he described included raising the price of water, providing incentives for adopting more irrigation-efficient technologies, and developing the local institutions to manage this process. Reaching these goals, he felt, would assure China’s future food security.
