Nutrient enrichment of water bodies continues to be a significant risk globally to human health and ecosystems. Stream restoration is sometimes considered a best management practice to control nutrients. Regenerative Stormwater Conveyance (RSC) is a restoration approach based on engineering stream channels to incorporate shallow pools, riffles, and grade controls to increase storm water retention and control erosion, and adding a carbon layer to the stream bed (e.g. wood chips) to enhance microbial processes like denitrification. This study examines RSCs effects on nutrients (P and N) and trace metals at two RSC sites 5 and 7 years post-construction, using combined field and lab measurements.
Field measurements showed that RSCs usually had lower DO and pH relative to nearby untreated stream reaches, but did not have consistently different P, N, dissolved organic carbon (DOC) or trace metals (Fe and Mn). No consistent longitudinal change in any water quality parameter was observed across sites. In lab experiments, we observed consistent removal of N and P when sediment was amended with wood chips and leaf litter suggesting that organic matter additions to stream substrates are important drivers of nutrient transformation in RSCs. The effects of RSCs in the field appeared to be swamped by seasonal leaf litter inputs where N was extremely low in the RSC site that had more extensive riparian area and more visible leaf litter biomass. Nutrient management effectiveness in RSCs may depend upon quantity and quality of organic matter added to the stream bed but also as supplied from the adjacent riparian zone.