Engineered headwaters can act as sources of dissolved organic matter and nitrogen to urban stream networks

Improved management of urban stream water quality requires identification of sources contributing excess nutrients and organic matter. While soils and lawns are potential nonpoint sources characterized by large pools of carbon (C) and nitrogen (N), their hydrologic connectivity to streams is often low relative to impervious surfaces. In contrast, engineered headwaters (gutters and pipes) retain smaller pools of C and N, but efficiently process litter into dissolved organic matter and are highly connected to streams during storms. We found that engineered headwaters have the potential to provide more than enough dissolved C and N to account for streamflow fluxes during storms. This finding suggests that engineered headwaters can act not only as stormwater conveyances, but as important proximate sources of dissolved carbon and nutrients to streams during storms. A nested mass balance approach like the one used here can further understanding of the contributions of previously overlooked subsystems, such as engineered headwaters, to biogeochemistry and element flux in urban catchments.