How to find normal water level in a stormwater pond or wetland
Each stormwater pond or wetland has some sort of device to control the water levels between and during storms. The picture below shows one such device. The horizontal part of the small PVC pipe marks the "normal" water level (a.k.a. permanent pool) where the water is supposed to stay most of the time.
Survival of the plants depends upon installing them at the right elevation relative to this "normal" water level.
Plants used in stormwater systems naturally group themselves into 4 categories of preferred water level: at normal water level, from normal water level up 12 vertical inches, from normal water level down 6 vertical inches, and more than 6 vertical inches below normal water level.