Water Level Fluctuation and the Great Lakes Wetlands

Water levels in Great Lakes coastal wetlands fluctuate over several time scales: yearly, seasonally, and daily. Each lake's hydroperiod- the signature of water-level rise and fall- is composed of several superimposed cycles with varying predictability. The great range of water-level fluctuations in the Great Lakes is unique among freshwater wetlands and is due to the enormous size of these basins and their watersheds as well as their locations in snow-producing latitudes. As with all wetlands, however, hydrodynamics control wetland properties, including habitat structure and ecosystem functions. Thus, decisions about controlling lake levels should also consider how curtailing natural water-level fluctuations would affect wetlands.