Effectiveness of streamside management zones on water quality: pretreatment measurements
The objective of this paired watershed study is to quantify the effects of upland forest harvesting and Streamside Management Zones (SMZs) on stream water quantity and quality in North Carolina. Four watersheds ranging from 12 to 28 hectares (i.e., two on Hill Forest and two on Umstead Research Farm) with perennial stream channels were gauged for flow monitoring and water quality sampling. We are also monitoring two additional larger (i.e., 32 and 46 hectares) watersheds at Hill Forest. The study started in 2007 and the first two years will be used to calibrate watershed runoff and stream water quality. During year three, one watershed from each pair will be treated. The treatment watersheds will be completely harvested with the exception of the SMZs, which will be maintained according to the NC ‘Neuse River Buffer Rules’ (a mandatory 50-foot buffer along streams in the Neuse River Basin). The two remaining watersheds will remain undisturbed as controls. A severe drought in 2007 caused one of the streams in the Umstead watershed to stop flowing, so it was excluded from analysis. Pretreatment daily runoff (measured in mm/day) from the two smaller paired and two larger watersheds at Hill Forest were significantly correlated (r2 0.93, p = 0.0001 and r2 0.96, p = 0.0001, respectively). We also found that turbidity, total suspended solids, and discharge were generally related to precipitation. We will continue to monitor the watersheds to document SMZs influence on water quality and understand the hydrologic process of headwater piedmont watersheds.