Hydrology and nutrient biogeochemistry in a created river diversion oxbow wetland

A better understanding of the function of riparian wetlands is needed. In this study, hydrological, successional, and water-quality dynamics are documented for a whole-ecosystem study involving a 3-ha created riparian wetland at the Schiermeier Olentangy River Wetland Research Park at The Ohio State University in Columbus, Ohio, USA, during 2003 and 2004. This wetland typically receives seven or eight natural weeklong flood pulses each year from the Olentangy River. Of 21 species planted in 1997, only Scirpus americanus and Juncus effusus remained as important macrophyte species during the study 6–7 years after planting. Typha spp., a naturally colonizing species, was the dominant macrophyte in most of the wetland. Mean retention rates per flood pulse for nitrate-nitrite, total Kjeldahl nitrogen (TKN), soluble reactive phosphorus (SRP), and total phosphorus (TP) were 0.71 g-N m−2, 0.92 g-N m−2, 0.016 g-P m−2, and 0.08 g-P m−2, respectively. The annual reductions of N-NO3−, TN, P-SRP, and TP were 74%, 41%, 46%, and 31% by mass. A greater attenuation of NO3− and TP occurred in the emergent marsh section of the wetland than the open water section. Conversely TKN increased through the emergent marsh and decreased through the open water section. Overall, the oxbow design is successful in ecological terms and we recommend that similar diversion wetlands be created in other locations to examine their function under different climatic and hydrological conditions.