BMP Impacts on Sediment and Nutrient Yields From an Agricultural Watershed in the Coastal Plain Region

Abstract

The goal of the Nomini Creek watershed monitoring study was to quantify the effectiveness of BMPs at the watershed scale and to determine if the improvements in water quality could be sustained over a long-term period. Information on the long-term effectiveness of BMPs is critical since BMPs are being implemented under the state cost-share program to reduce nonpoint source pollution (NPS) to the Chesapeake Bay. The Nomini Creek project started in 1985 and was completed in 1997. A pre-versus post-BMP design was used. A combination of managerial and structural BMPs was implemented. Major BMPs implemented in the Nomini Creek watershed included no-tillage, filter strips, and nutrient management. The data collected at the 1463 ha Nomini Creek watershed consisted of land use, hydrologic, water quality, soils, and geographical information.The BMPs implemented at Nomini Creek reduced average annual loads and flow-weighted concentrations of nitrogen (N) by 26% and 41%, respectively. Average annual total-N loads discharged from the watershed were reduced from 9.57 kg/ha during the pre-BMP period to 7.05 kg/ha for the post-BMP period. Largest reductions were observed for dissolved ammonium-N, soluble organic-N, and particulate-N. In contrast, nitrate-N loads increased after BMP implementation. Increase in nitrate exports was likely due to ammonification and nitrification, and subsequent leaching of particulate-N species that were conserved on the field. In comparison to N, reductions in phosphorus (P) loads and concentrations were not significant. BMP implementation resulted in a mere 4% reduction for total-P with a corresponding 24% reduction in flow-weighted concentration. The average annual total-P loads exported from the watershed were 1.31 and 1.26 kg/ha for the pre-and post-BMP periods, respectively. Reductions in total-P loads were due to decreases in particulate-P. Exports of ortho-P and dissolved organic-P increased after BMP implementation. It is likely that some of this post-BMP increase in dissolved P fractions was associated with dissolution and leaching of particulate-P, and higher rainfall-runoff activity in the watershed during the post-BMP period. In comparison to nutrients, there was no significant change in suspended solids discharged from the watershed. Overall, the findings of this study indicate that the BMPs were effective in reducing the losses of some forms of nutrients, such as ammonium-N and particulate-P, from the Nomini Creek watershed, but additional BMPs are necessary to achieve significant reductions in all forms of N and P.

Effect of Coal Combustion By-products on Phosphorus Runoff from a Coastal Plain Soil

“…It is important to note that the rates of erosion observed in the current study, although substantial, were not uncharacteristic for coastal plain soils in the region. Elsewhere, Inamdar et al (2001) reported annual erosion rates of only 0.9-1.1 Mg ha −1 from a row-cropped watershed on the coastal plain of Virginia.…”

Hydrologic Response Unit Routing in SWAT to Simulate Effects of Vegetated Filter Strip for South-Korean Conditions Based on VFSMOD

“…Vegetative Filter Strip (VFS) is one of most effective BMPs to reduce sediment load and pollutants from agricultural fields [3][4][5][6][7][8]. VFS is usually installed at the edge of agricultural areas or the areas along streams, and it is designed to remove not only sediment load but also other pollutants, such as nutrients from runoff by filtration, infiltration, adsorption, absorption, deposition, decomposition, and plant uptake [4].…”

The Stream and Its Altered Valley: Integrating Landscape Ecology into Environmental Assessments of Agro-Ecosystems

“…Most of these studies, however, have only measured the effectiveness of specific project types at small scales (e.g. Sheiffield et al, 1997;Cey et al, 1999;Weigel et al, 2000) and only a few have measured the aggregated effectiveness of a variety of project types at a watershed scale (Cook et al, 1996;Edwards et al, 1996;Inamdar et al, 2001;Inamdar et al 2002). These watershed scale studies have generally been conducted on a single watershed.…”