Paper No. J06109 of the Journal of the American Water Resources Association (JAWRA). © 2008 American Water Resources Association. Discussions are open until August 1, 2008.
Nitrate Removal in a Restored Spring-Fed Wetland, Pennsylvania, USA1
Article first published online: 10 JAN 2008
JAWRA Journal of the American Water Resources Association
Volume 44, Issue 1, pages 222–234, February 2008
How to Cite
Woltemade, C. J. and Woodward, J. (2008), Nitrate Removal in a Restored Spring-Fed Wetland, Pennsylvania, USA. JAWRA Journal of the American Water Resources Association, 44: 222–234. doi: 10.1111/j.1752-1688.2007.00149.x
- Issue published online: 10 JAN 2008
- Article first published online: 10 JAN 2008
- Received August 7, 2006; accepted July 9, 2007.
- hydraulic retention time;
ABSTRACT: In 2001, the 1.04-ha Hornbaker wetland in south-central Pennsylvania was restored by blocking an artificial drainage ditch to increase water storage and hydraulic retention time (HRT). A primary goal was to diminish downstream delivery of nitrate that enters the wetland from a limestone spring, its main source of inflow. Wetland inflow and outflow were monitored weekly for two years to assess nitrate flux, water temperature, pH, and specific conductivity. In Year 2, spring discharge was measured weekly to allow calculation of nitrate loads and hydraulic retention time. Surface runoff was confirmed to be a small fraction of wetland inflows via rainfall-runoff modeling with TR-55. The full dataset (n = 102) was screened to remove 13 weeks in which spring discharge constituted < 85% of total inflows because of high precipitation and surface runoff. Over two years (n = 89), mean nitrate-nitrogen concentrations were 7.89 mg/l in inflow and 3.68 mg/l in outflow, with a mean nitrate removal of 4.19 mg/l. During Year 2 (n = 47), for which nitrate load data were available, the wetland removed an average of 2.32 kg N/day, 65% of the load. Nitrate removal was significantly correlated with HRT, water temperature, and the concentration of nitrate in inflow and was significantly greater during the growing season (5.36 mg/l, 64%) than during the non-growing season (3.23 mg/l, 43%). This study indicates that hydrologic restoration of formerly drained wetlands can provide substantial water quality benefits and that the hydrologic characteristics of spring-fed wetlands, in particular, support effective nitrogen removal.