August 2013 health advisory due to high algae levels. For more information: www.healthoregon/hab. Fern Ridge Lake is a popular recreation area for water sports, such as windsurfing, sailing, water skiing, flat water kayaking, stand up paddling, swimming and fishing. Extensive wetlands provide opportunities to view waterfowl and other wildlife. Fern Ridge is southern Willamette Valley's largest reservoir at 9,000 acres. It was created for flood control in 1941 by damming the Long Tom River. In the summer it is maintained at its maximum and in the winter it is drawn down.