A city is celebrating St Patrick’s Day – by dying their river green. Tampa in Florida has transformed its Hillsborough River to mark the annual celebration of all things Irish. Kick-started with the so-called River O’Green Fest held last Sunday, the stretch of water will retain its hue until the big day on Thursday. Ashly Anderson, of the Tampa Downtown Partnership, explains: “The river is going to turn a bright Kelly Green to celebrate St. Patrick’s Day."It’s a food safe dye and it’s done by the city of Tampa’s water department. “Hundreds of gallons of biodegradable food safe dye will be put into this river to make it a bright shade of green.” The dye is reportedly safe for humans and wildlife, and is usually used in food and in eye surgery to trace blood vessels. The biodegradable dye will gradually dilute and wash away.