Walton Dune Lakes

The coastal dune lakes of Walton County are among the rarest kinds of lake on Earth. Fifteen named lakes lie behind the dunes along roughly 26 miles of the county's Gulf shore, and lakes of the same kind are otherwise known in only a handful of places, among them Madagascar, Australia, New Zealand and the Pacific Northwest. Western Lake, beside Grayton Beach State Park, is one of the largest of them. What makes them unusual is that they are neither fully fresh nor fully salt. Rain, groundwater and streams fill the lakes with tea-colored fresh water until the level rises high enough to break through the dunes. The lake then drains to the Gulf through a channel called an outfall, and at times the tide pushes seawater back in. The outfall may stay open for days or months before sand closes it again. Because the balance shifts constantly, a single lake can hold freshwater fish on one visit and saltwater species on the next, and the plant and animal communities along its shore change with it. The lakes sit among some of the most expensive coastline in Florida, and their outfalls pass under beach houses and between resort towns. Their shallow basins and slow-flushing water make them sensitive to runoff from lawns and roads, and Walton County and the Choctawhatchee Basin Alliance monitor their water quality.