A large natural lake just to the north of the town of Anmore. Only the south end of the lake is accessible for vehicles but there are extensive hiking trails all around the perimeter.
Lake where Laura's body is found in episode #512 "Dual Spires".
Source: Psych Forums
Lake where the strange drownings are occurring in episode 1x03 "Dead in the Water".
Liv wakes up inside a body bag on the beach after the ill-fated boat party in pilot episode.
A young girl disappears while her family is camping by the lakeside in episode 1x04 "Conduit".
Source: XF Marks the Spot
Carter and Stark go to talk to Dr. Todd while he is fishing on the lake in episode 2x02 "Try, Try Again".
The SG teams are evacuating the inhabitants of this planet during a Goa'uld assault in episode 2x02 "In the Line of Duty".