was a body of water between Sumas
mountains, midway between the present-day cities of Chilliwack
, British Columbia
. Its name means "a big level opening" and is a reference to the site of the lake, which lay between Sumas Mountain
and its American counterpart, Sumas Mountain
, Washington, part of the foothills of the Cascade Mountains
. The lake extended into Whatcom County
, Washington, necessitating a railway trestle of the British Columbia Electric Railway
across it from Huntingdon
to the foot of Vedder Mountain remains today as a dyke.
Originally, the lake occupied 40 km² (15 mi²) and swelled to 120 km² (47 mi²) during flooding. The lake was drained in order to create more farmland in the fertile region of the Fraser Valley and also to reduce mosquito infestations in the region. The flow from the Vedder (Chilliwack) River was redirected into the Vedder Canal in 1924 under a plan developed by engineer Fred Sinclair, effectively draining the lake. Another drainage channel, the Sumas Lake Canal, runs along what is now Sumas Prairie's northwest side at the foot of Sumas Mountain.