Long parallel lines of bubbles are often seen on the lake surface when the wind speed exceeds about 11 km/hr but is less than about 45 km/hr (when the pattern breaks up). Judging by the sparcity of white caps in the pictures, below, the wind speed was likely between 20 to 30 km/hr.
The wind drags on the surface waters of the lake and causes helical rolls to form in the upper layers of the lake. The axes of these rollers lie more or less along the wind direction. Pairs of rollers turn in opposite directions rather like the wringers on old–fashioned washing machines. Surface water flows inward and sinks between a pair of adjacent rollers, but the bubbles (and other floating debris) are left as lines on the surface.
This pattern of wind–driven helical rolls in the surface waters of the lake is called a Langmuir Circulation, after Irving Langmuir who first explained its structure after observing similar lines of seaweed during an ocean crossing in 1938.
A good place to observe Langmuir Circulation on Kootenay Lake is from the Nelson Bridge during a brisk westerly wind.
While walking along the highway in early September I noticed even more distinct parallel lines of white water-bubbles [Langmuir Circulation] on the water’s surface about 2km east of the bridge. A very intriguing phenomenon.
Although I have seen the pattern many times on the Lake, it was your September observation which prompted me to try to take a picture of it. I know it can be much more spectacular than the pictures I show here, so I will continue to watch with camera in hand. I imagine that another good viewing platform would be the Main Lake ferry mid crossing when there is a brisk southerly wind.