Eighty-three Mile Lake contains sodium carbonate-rich brine, and is located 500 metres west of Highway 97, 25 kilometres south of 100 Mile House.
The lake is is a semi-evaporitic playa lake. It is located in the "Green Timber Plateau" area (EMPR Bulletin 4), a semi-arid plateau area averaging 1130 metres elevation which is part of the Cariboo Plateau. The area is underlain by alkaline plateau basalt flows of the Miocene to Pleistocene Chilcotin Group, mantled by a thin cover of glacial till and glaciofluvial sediments. Annual precipitation averages between 300 and 400 millimetres (EMPR Paper 1991-1).
Eighty-three Mile Lake in 1937 (EMPR Bulletin 4) covered an area of approximately 12 hectares and contained brine to a maximum depth of about 60 centimetres. At 16 degrees celsius, the brine had a density of 1.085 and contained 4.85 per cent solids. The solids were composed of 97.2 per cent sodium carbonate and 2.8 per cent sodium chloride. No "winter crystal" (crystalline sodium carbonate minerals) is known to precipitate in the brine.