The Long-term Response of Nutrient and TSS Loads to an Agricultural Stream Restoration in Coastal plain of North Carolina

A growing number of restoration projects have been undertaken to counteract the adverse effects of stream degradation in United States. However, there is a lack of research and understanding on the immediate, mid-, and long-term effects of stream restoration on water quality due to 1) no or very partial data on the hydro-chemical footprint of a stream before and after restoration; 2) large uncertainties associated with existed infrequent measurement techniques on material loads. To characterize precise hydro-chemical signature of the stream, we applied the state-of-the-art in-situ sensor, i.e., ultraviolet-visible (UV-Vis) spectrophotometers and Doppler velocity meters, to capture high-frequency water quality and flow data at three monitoring stations upstream (UP), middle (MD), and downstream (DN) pre- and post-restoration along a 2.2 km long stream at Goldsboro, NC. To avoid counting the effects of load entering at UP station, we treat UP station as the reference, MD and DN stations as the treatment. The absolute changes in cumulative loads between treatment and reference stations are indicative of restoration effects on water quality.

The results indicated that there is a remarkable downward inflection of 66% and 62% in the expected nitrate loads at the MD and DN stations, respectively, 6 months after restoration. We hypothesize that these large benefits are due to the fact that the stream has become a flowing wetland. We hypothesize that the immediate water quality benefits would continue beyond this.