Quantifying the Water Quality Functions of Wetlands

A recent Supreme Court ruling has put thousands of small, seemingly isolated wetlands at greater risk and accelerated the loss of coastal freshwater wetlands. Although each wetland is small, their cumulative benefits are most likely highly significant. It has been demonstrated, primarily with studies involving constructed treatment wetlands, that wetlands improve water quality and reduce levels of a wide array of pollutants. However scientifically based methods for predicting how well a particular wetland will improve water quality are limited. Furthermore, such estimates are rarely verified by field sampling. We outline a method for estimating the water quality function associated with wetland characteristics (hydraulic detention time, vegetative density, catchment land use, etc.) that is based on a combination of functional analyses and field sampling. This method incorporates what is known about the fate and transport of pollutants in wetlands with landscape characteristics that influence the opportunity and significance of each wetland's functional capacity.