Free-water Depth As A Management Tool For Constructed Wetlands

• Published in: Journal of aquatic plant management 2002-01, Vol.40 (1), p.43-45
• Main Authors: Borst, M, Riscassi, AL, Estime, L, Fassman, EL
• Format: Article
• Language: English
• ISSN: 0146-6623

The EPA's National Urban Runoff Program (Athayde 1982) conducted several decades ago clearly showed contaminants exist in urban runoff and more recent research shows that constructed wetlands can lower the concentration of unwanted compounds in stormwater runoff (Stockdale 1991, Wu 1995, Watanabe 1997). Although wetlands constructed to treat stormwater runoff are increasingly-used to help meet environmental goals, the understanding of this application lags behind the understanding of wastewater treatment. As stormwater applications increase, the need to understand internal wetland processes and the management options becomes proportionally more important. Studies are underway in our laboratory to gain a more thorough understanding of selected operating processes within a constructed stormwater wetland. Early experiments in our lab failed to produce desired vigorous plant growth within the test wetland cells, although the selected water depths were well within the established ranges for the mature species (Woodland 1991). One suspected cause of the inhibited growth was the freestanding water in the cells during the sprouting stage. Wetland plants which are able to establish themselves in the same water depths as the mature parental strain are known to have shared responses to the environmental gradient. On the other hand, plants that cannot establish themselves in the same water depth as the mature parental strain have some distinct responses to water depths (Keddy and Ellis 1985). Wetland species are further classified into two major groups based on the water depth establishment requirements. Drawdown species establish themselves when there is no standing water, and standing water species establish themselves when water is present (Keddy and Ellis 1985). This study was conducted to compare the growth of three wetland plant species grown in three different water depths. Management techniques for an established wetland are somewhat limited, but matching the free water depth with selected species is a potential technique to control specific plant communities. The design of the wetland can incorporate features enabling users to control or select water depth. Plant attributes affected by the water depth can be indirectly controlled using these wetland design features.