New Morton County lake fills unexpectedlyRunoff from heavy winter snowfall has filled a new manmade lake north of Mandan at least a year ahead of schedule. Harmon Lake in Morton County is part of a flood control operation. Known technically as Dam No. 6, it is part of the Square Butte Water Shed plan. The lake will operate as both a recreation area and spillway/dam for runoff from the watershed west of state Highway 25.