Before revision: The lower picture shows the same lake, but with a outlet barrier and an installed Olszewski tube, the upper end of which passes through the barrier into the outlet and the lower end of which is at the lowest point of the lake.
After revision: The lower picture shows the sanme lake, but with a outlet barrier and an installed Olszewski tube, the upper end of which passes through the barrier into the outlet and the lower end of which is at the lowest point of the lake.