Lake Hemnessjøen is located in the Aurskog-Høland Municipality in Akerhus County and Trøgstad in Østfold County. The lake is surrounded by a superb traditional landscape, including several exciting wetland reserves with rich bird communities.
The lake is located in the northern end of the Haldenvassdraget lake district and offers especially good pike fishing. It has varying depths, but is dominated by shallow sections filled with fish. Housing is spread out in small group along the waterway. Farming is concentrated in the Aurskog-Høland Municipality, while in Trøgstad the lake is framed by forests. The deepest part is 35 metres and the average depth is around 8 metres.