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Is Kentucky Limestone Water Indispensible for Bourbon?

Water is an essential ingredient in bourbon. And many local distillers have long said the commonwealth’s unique limestone water distinguishes Kentucky bourbon from competitors. But how important is it really?To legally be called bourbon, the spirit has to be made of mostly corn. It has to be aged in new charred-oak barrels. And it has to be made in the United States. There's no rule that dictates what type of water is used, but many local distillers say no matter what the law says, bourbon isn't bourbon unless it's made with limestone water.It's a stipulation that goes back to the early days of bourbon. University of Kentucky geology professor Alan Fryar says it was easy access to limestone water that played an integral role in launching the bourbon industry here centuries ago.“I found intimately connected with the emergence of bourbon-making in this part of the country that limestone water was what we had in the late 1700s when people started making bourbon in this area,” he says.The allegiance to limestone water isn't just superstition. It has a high pH, which promotes fermentation. The limestone adds minerals, like calcium. It filters out impurities, most importantly iron, which gives liquor a bad taste.Kentucky’s limestone water was perfect for those early distillers who developed bourbon, and it explains why the industry is centered here. But is it still a necessity for modern distillers?At the Maker's Mark Distillery in Loretto, there’s a spring of limestone water running through the property. It once turned the distillery’s grist mill and provided the water for bourbon.Today, Maker's Mark draws its water from a lake on its bucolic Marion County campus. It's part of the brand's ties to its home. As Master Distiller Greg Davis begins telling me about all of the company’s wildlife management practices on the property, a large buck appears on the hill, almost like it's staged.“Oh, he’s just giving us the flag,” Davis whispers, pointing to the buck’s white tail. “He kind of came back this way. He’s right at the roof tip of that warehouse.”Maker's Mark owns nearly 700 acres around the lake, in an effort to protect the water from agricultural runoff. They actively manage the wildlife habitat around the lake—and Davis says the company is committed to maintaining the water's integrity.“You know, it’s not about taking raw water and then trying to treat it or trying to do something with it,” he says. “That’s what Mother Nature is for. And she’s already filtering it and doing all the work through the limestone for us, let’s help her by helping what we have here.”But other distillers don’t have access to a perfect water source, or they produce too much bourbon to rely on a lake or spring.Louisville-made Old Forester uses city water to make its bourbon. Brown-Forman master distiller Chris Morris says the company used to use alluvial limestone water that ran beneath the city, but it's been contaminated for years. Now, the water from the Louisville Water Company is treated with a process called reverse osmosis before it ends up in a bottle of Old Forester.Morris says for his bourbon, limestone water isn’t necessary.“Well limestone water is wonderful to have if you can use it, if you have it,” he says. “But it is not essential.”Gable Erenzo agrees. He’s a distiller at Tuthilltown Spirits, which makes liquor—including bourbon—in New York’s Hudson River Valley. There’s actually some limestone in that region, too. But Erenzo says the water is only one small part of a bourbon's flavor profile. Think of the concept of terroir, often used with wine: this idea that geography, geology and climate all come together to create a unique product.“So I think the three main things that will create a specific regional flavor profile for whiskey or for bourbon in general would be the water, the grain and the yeast,” Erenzo says.And bourbon brands have adjusted to create their own special flavors—whether that’s dependent on limestone water or not.Alan Fryar of UK says even if special Kentucky water isn’t exactly essential to bourbon production anymore, the myth adds to the overall effect.“I think that’s where the concept of terroir comes in, where it’s not just physical factors, but it’s also what the consumer perceives as the place, the origin of the spirit that gives it value,” he says.“So it’s branding?” I ask.“Yeah, basically.”Greg Davis of Maker's Mark says for his company, using limestone water is about more than branding—it’s a key ingredient. But that doesn’t mean other distillers don’t successfully create bourbon by placing less emphasis on the water.“It’s just not going to be steeped in the history of what is traditional bourbon,” he says.This story is part of WFPL's Food & Drink Week. We'll be exploring dining and libations in the Louisville area ahead of Thanksgiving. You'll find new stories  hereeveryday through the holiday.