This photo was taken in Washington State, in the Cascade range. The mountain you are looking at is called Mt. Baker, and it is actually a volcano.  This picture was taken in mid-July while on a hike around the lake. While I couldn’t manage to find a photo of one of the rivers in the area, Mt. Baker is a glacier, and produces large amounts of runoff. It stands at almost 11,000 feet, and the elevation in this picture was around 3,000 feet, so the elevation gain from the lake to the top is massive.