China has an incredible number of mouths to feed, and even with food imports from the U.S. booming, those hungry mouths require a whole lot of farmland. That farmland, meanwhile, requires the second-largest irrigation network in the world.Now, it’s pretty intuitive to worry about the environmental impact of all that water use, especially considering we’re drying up worldwide. But there’s another problem afoot: China is the world’s largest carbon emitter, and according to new research, the pumping equipment for its irrigation network puts out a ghastly 33 million tons of CO2 per year.A team led by Professor Jinxia Wang of the Centre for Chinese Agricultural Policy published a paper in Environmental Research Letters that drops some big numbers: 70 percent of China’s grain comes from agriculture, and the amount of wheat required for a "small loaf of bread" requires 500 liters of water on its own. Country-wide, that’s an absurd amount of water, much of which gets pumped out of deep wells that have an average depth of 70 meters in some areas.“Improved access to pumping technology, cheap energy and the ability to directly control water availability has led to a massive expansion of groundwater pumping across large parts of Asia, particularly in China and India," Wang said. "The small scale of pump operations makes regulation and control of use extremely difficult.”According to the report, the amount of groundwater used for irrigation has increased from 10 billion cubic meters in 1950 to more than 100 billion today. All that water pumping requires a ton of energy."Generally, there is a surprising gap in research knowledge about the energy required for water use," Professor Declan Conway, an author of the report, said. "Irrigation is fundamental to food security in China as it is the world’s second largest irrigator. It is vital that we understand the sources of greenhouse gas emissions in agricultural water use to design and implement sustainable policies for the future."Agriculture is responsible for about 17 percent of China’s carbon emissions yearly. The pumping infrastructure itself was responsible for 0.5 percent of China’s total carbon output. While that may not seem like a lot as a proportion of China’s prodigious output, it’s still a massive amount in total. It highlights the fact that, as the world grows, intelligent decisions have to be made in terms of water usage and clean infrastructure to minimize the downsides of compromise."Water scarcity in China is already driving policies to improve water conservation so it is crucial to identify water-energy trade-offs and potential co-benefits," Sabrina Rothausen, another author of the paper, said. "Our results suggest that an integrated policy approach could promote considerable water and energy savings."Follow Derek Mead on Twitter.
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