Jacob's Well is a perennial karstic spring in the Texas Hill Country flowing from the bed of Cypress Creek, located northwest of Wimberley, Texas. The twelve foot (four meter) diameter mouth of the spring serves as a popular swimming spot for the local land owners whose properties adjoin Cypress Creek. From the opening in the creek bed, Jacob's Well cave descends vertically for about thirty feet (ten meters), then continues downward at an angle through a series of silted chambers separated by narrow restrictions, finally reaching a depth of one hundred and twenty feet (forty meters). Until the modern era, the Trinity Aquifer-fed natural artesian spring gushed water from the mouth of the cave, with a measured flow in 1924 of one hundred and seventy gallons per second (six hundred and forty liters per second) discharging six feet (two meters) into the air. The spring is the greatest source of water recharging the Edwards Aquifer.

A sign advising to pray for rain hangs above an exhibit area at the 47th Annual World Ag Expo in Tulare, February 12, 2014. About a hundred years ago, when urban water systems were being developed throughout the state, the city of Sacramento wrote protections from metering into its charter, vowing that residents would always have the right to use as much water as they needed. But on Tuesday, the state's top water regulators released a framework for enforcing California's first statewide mandatory restrictions on urban water use – cuts of 25 percent for non-agricultural users ordered last week by Democratic Governor Jerry Brown as a devastating drought enters its fourth year. (Photo by David McNew/Reuters)

An emu runs to escape an approaching wildfire as it burns near Potero, California, U.S. June 20, 2016. (Photo by Mike Blake/Reuters)

Chelsea Hughes, 25, sings at the first annual Underwear Karaoke, an event that pairs two common fears: being seen in your underwear and singing in public, in Los Angeles, California March 12, 2015. (Photo by Lucy Nicholson/Reuters)

This Sunday, September 7, 2014 photo provided by Rachel Kirk shows smoke from a fire rising above Little Yosemite Valley near Yosemite National Park, Calif. (Photo by Rachel Kirk/AP Photo)

These are incredible pictures of skilled aircraft pilots flying through raging infernos to put out enormous flames. Daredevil Italian photographer Antonio Grambone, 46, jumped up close to the blaze to capture the incredible images of forest fires in the National Park of Cilento and Vallo di Diano, in the province of Salerno in Italy. At great risk to himself, Antonio captured these incredible shots making them appear like Italian masterpieces.

Photo: On target: Brave pilots are on a course straight into these enormous flames as they release tonnes of water onto the fire. (Photo by Antonio Grambone/Caters News Agency Ltd)

Sunset is seen through smoke from the Wallow fire June 8, 2011 in Springerville, Arizona. Hundreds of thousands of acres have burned in eastern Arizona prompting evacuations by residents. Smoke loomed over the twin towns of Eager and Springerville, home to about 7,000 people north of the fire. (Photo by Eric Thayer/Getty Images)

These spectacular landscapes may look like something from another planet – but they are in fact colorful salt ponds which stretch for miles. Despite being better known for tech companies and expensive property – San Francisco, California is also home to this vibrant quilt of color spanning the South Bay Area. From eerie green pools to gothic shades of red the surreal landscapes are caused by the organisms or micro-algae living within them. Photo: Aerial view of the salt ponds in San Francisco, California. (Photo by Cris Benton/Caters News)