No, these aren’t the ruins of an ancient amusement park in Western China. These two water wheels on the Tashkurgan River are part of the irrigation system that helps keep the 13,000 or so residents of Tashkurgan supplied with fresh water even though the region receives less than 3 inches of precipitation each year. That reliable access to fresh water is one of the reasons this area has been inhabited for thousands of years and made it an important stop on the ancient Silk Road trade route. Highlighting the importance of fresh water is the goal of World Water Day, which falls on March 22 every year. This year’s theme is "Leaving no one behind." With over 2.1 billion people living without safe water at home, it’s one of the most ambitious of the UN’s Sustainable Development Goals.