At the Pelican Hill golf resort in Newport Coast, Calif., water conservation is an obsession. Yuki Shimazu/Flickr hide caption

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Workers pick asparagus in early April at Del Bosque Farms in Firebaugh, Calif. This year, some farmers in the state will get water, others won't, based on when their land was first irrigated. David Paul Morris/Bloomberg/Getty Images hide caption

itoggle caption David Paul Morris/Bloomberg/Getty Images

Students at the Pennsylvania College of Technology are learning a technique called "tripping pipe," moving a pipe from a stack into a horizontal position and lowering it down into a well. The students train on a practice drilling rig to learn how to be roustabouts. Jeff Brady/NPR hide caption

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An undated file photo provided by the Wisconsin Department of Natural Resources of a northern long-eared bat. A fungal disease has devastated the species, now listed as threatened. AP hide caption

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Poland's second-largest city is also a major tourist destination. Krakow (seen here at night from the Krakus Mound) is suffering some of the worst air pollution in Europe. Arek Olek/Flickr hide caption

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The Mariposa border crossing, as seen from Nogales, Ariz., September 2013. This land port serves as the main point of entry into the U.S. for fresh produce from Mexico. A lot of that produce gets rejected just past the border, even though it's perfectly tasty and edible. David Kadlubowski/Corbis hide caption

itoggle caption David Kadlubowski/Corbis

Fields of carrots are watered March 29, 2015, in Kern County, Calif. Subsidized water flowing in federal and state canals down from the wet north to the arid south helped turn the dry, flat plain of the San Joaquin Valley into one of the world's most important food-growing regions. Frederic J. Brown/AFP/Getty Images hide caption

itoggle caption Frederic J. Brown/AFP/Getty Images