Coul Den's industrial past is tied to the Haig's Distillery in Markinch and Wemyss. The reservoir was built in 1900 to supply water for the distilleries bottling plants. The original dam had a surface area of 14.2 acres (5.75 Ha), a maximum depth of 42 feet (12.9 m) and a capacity of 75,135,200 gallons. When the Haig plant closed in 1989 the reservoir was closed and the water level reduced.
Coul Den has become an important site for breeding birds including Mute Swans, Tufted Ducks, Little Grebe and Common Sandpipers who have successfully bred around the edge of the loch. The site also provides a safe haven for migrant birds during the winter months.
The loch is surrounded by a variety of habitats, including, Swamp, Willow Carr, Tall Ruderal and Neutral grasslands.