ASSESSING THE WATER QUALITY DYANMICS IN RESTORED AND NATURAL CHANNELS DURING BASEFLOW AND STORMFLOW IN A SUBURBANIZING S.E. PIEDMONT WATERSHED

As part of a 10 year monitoring study a residual mass balance approach was applied to assess the instream transport and retention dynamics of sediment, nutrients, and organic carbon (OC) in two restored and two unaltered or “natural” stream reaches in a developing SE Piedmont watershed during different flow regimes. The restored stream reaches indicated the net retention of: total suspended solids (TSS), particulate, total dissolved, dissolved organic and total nitrogen (PN, TDN, DON, TN), particulate and total phosphorus (PP and TP), and organic carbon (OC) during baseflow monitoring periods. Whereas, the restored stream reaches exhibited a net export of TSS, NO₃-N, PP, TP, and particulate organic carbon (POC) during storm events. A predominately forested and unaltered stream reach exhibited a net retention of ortho-P and a decline in per unit flux of most of the other water quality constituents during baseflow and storm runoff events. The suburban unaltered stream reach with significant engineered stormwater control measures (SCMs) indicated the downstream mobilization of most the water quality constituents during baseflow and storm events. Our results indicate that channel restoration practices were successful in reducing nutrient and sediment transport during baseflow periods but six years after restoration these channel segments displayed net losses of sediment and some nutrient species in relation to unrestored "natural" channels.