Flat Reservoir   Be the first to submit input for Flat Reservoir. If you have info on Flat Reservoir, Carter County, Montana please submit it here to improve this web site.          These outdoors activities are available near Flat Reservoir.   Public Lands Near Flat Reservoir: Medicine Rocks State Park, Montana, 23 miles away   Camp Grounds Near Flat Reservoir: Lantis Spring Campground, Carter County, 7 miles away   Ski Areas Near Flat Reservoir: Terry Peak, South Dakota, 74 miles away       1100 foot drop, 6 lifts, 24 runs