Pac-Man farming and the disappearing Ogallala aquiferAt first glance, this 2000 Landsat 7 image of G

Pac-Man farming and the disappearing Ogallala aquiferAt first glance, this 2000 Landsat 7 image of Garden City in Kansas looks like an overly ambitious game of Pac-Man. But these rigid, circular patterns are actually crop fields, with tan circles representing harvested crops, and the red circles denoting healthy, irrigated crops. Central pivot irrigation created the Pac-Man motif of Garden City’s agriculture, and has transformed the local economy into America’s breadbasket powerhouse.Garden City is in the middle of the High Plains, a region in the Midwest known for its dry summers and winters with less than 45 cm of rain a year. When central pivot irrigation was first developed, it shifted Garden City from its dependence on sporadic rainfall to groundwater from the Ogallala aquifer. Farming in the High Plains now relies fully on the Ogallala aquifer, one of the world’s largest groundwater sources that spans from Wyoming to Texas.You’ve likely seen the equipment for central pivot irrigation before — a water pump that is extended down to an underground aquifer in the center of a crop field is connected to a wheeled pivot hooked up with sprinklers. The pivot slowly rotates around the field, spraying and irrigating the crops with fresh groundwater, creating the circular Pac-Man motif that is now synonymous with groundwater-dependent farming.Despite once having enough water to cover all fifty American states by half a meter, the Ogallala aquifer is slowly running dry. Annually, about one-fifth of the crops in the United States are grown using fresh groundwater from the Ogallala aquifer, a volume of water equivalent to that of 18 Colorado Rivers. The semi-arid climate of the High Plains doesn’t supply sufficient rainfall to naturally recharge the aquifer, and in some counties, the water table has decreased by as much as half a meter in one year. Researchers estimate that agricultural production using water from the Ogallala aquifer will begin to decline after 2040, but if farmers could lower groundwater usage by just 20 percent, the decline will only begin after 2070.But here is the real question — can the aquifer be sustained forever? Researchers estimate that it would take 6000 years for the aquifer to be naturally recharged. But for that to happen, farmers would immediately need to reduce their groundwater usage by 80 percent, which would dramatically lower crop production. That possibility is as realistic as beating the world record in a perfect game of Pac-Man — the Ogallala aquifer is an indispensable component of a $20-billion industry that exports crops and crop products to many parts of the world.So the original question remains — how much more can the Ogallala aquifer be preserved as a finite resource? Many farmers are already preparing for that day of reckoning by growing crops don’t need irrigation and require less water. Other farmers are developing new methods that don’t depend on groundwater: instead of completely plowing fields after harvest, new crops are planted in the residual stems, which helps to lower soil erosion and moisture loss from the soil. Federal programs also offer incentives to farmers who help conserve grasslands — 25 million acres of which have been converted to crop fields since 1982 — that can be used to graze cattle and buffalo. But at the same time, subsidies for irrigation-dependent crops, such as corn, soybeans, and cotton, are higher than that for grassland conservation, with national and worldwide demand for irrigation-dependent crops remaining as high as ever.So for many farmers, the choice to continue irrigating their crop fields with Ogallala groundwater is a straightforward one. However, the federal government and agricultural industry will eventually have to come to terms with the future of farming in the High Plains — farming using a water source that will not depend on the seemingly infinite Ogallala aquifer.-DCPhoto credit: https://earthobservatory.nasa.gov/images/2510/garden-city-kansas?src=veMore reading:http://on.doi.gov/1JszwjpMore on center pivot irrigation:http://bit.ly/1T1VSechttp://bit.ly/1FCuutmMore on the Ogallala aquifer:http://bit.ly/1Qxwedlhttp://wapo.st/1dk7QiDhttp://bit.ly/1Iq68dhIf you feel like trying against the world Pac-Man record:http://bit.ly/1eTY0VH -- source link

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