East of Devils Lake is Stump Lake. It becomes part of Devils Lake at a water level of about 1,447 feet (441 meters) above mean sea level. By the 2011 image, a channel connects the two water bodies.
When Devils Lake reaches a level at which it overflows, 1,458 feet (444.4 meters) above mean sea level, water would spill from Stump Lake through Tolna Coulee into the Sheyenne River. The U.S. Army Corps of Engineers completed a control structure at Tolna Coulee in 2012.
The Tolna Coulee control structure is essentially a dam designed to prevent uncontrolled overflow from Stump Lake. An uncontrolled overflow could cause significant flooding damage downstream. Furthermore, water in Stump Lake has more sulfates than the water in western Devils Lake. Large volumes of water flowing uncontrolled through Tolna Coulee could cause water quality problems for communities downstream.