Birch Lake has a surface area of 32 acres and is two miles downstream of Bone Lake. Nielsen Lake's landlocked watershed discharges groundwater flow towards Birch Lake. Birch Lake is considered a shallow lake or wetland with 100% littoral area shallow enough to support emergent and submerged aquatic plants. Birch Lake is identified in name as a lake but was determined by the State to be a wetland due to its physical characteristics. Therefore it is not listed for a water quality impairment. The lake has been identified by CLFLWD to be a key factor influencing the water quality of School Lake and Little Comfort Lake. A survey in 2008 identified a diverse plant population in Birch Lake with little curly-leaf pondweed present.