Browsing by Author "Inamdar, S. P."
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- BMP impacts on sediment and nutrient yields from an agricultural watershed in the coastal plain regionInamdar, S. P.; Mostaghimi, Saied; McClellan, P. W.; Brannan, Kevin M. (American Society of Agricultural and Biological Engineers, 2001)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 ammonfication 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 BMIs are necessary to achieve significant reductions in all forms of N and P.
- Relationships between drainage area, slope length, and slope gradient for riparian slopes in VirginiaInamdar, S. P.; Dillaha, Theo A. III (American Society of Agricultural and Biological Engineers, 2000)Surface runoff and interflow generated on riparian hillslopes concentrate along rills or topographic depressions as they move downslope. This runoff concentration is an important factor that determines the effectiveness of conservation practices such as vegetated filter ships and riparian buffers and needs to be accounted for while designing such practices. Currently, routinely available DEMs are not detailed enough to capture the runoff concentration that occurs at the hillslope scale. This article investigated the possibility of developing simple relationships that could be used to quantify specific or total contributing areas in terms of hillslope attributes such as slope length or gradient. Riparian hillslopes in the Ridge and Valley region of Virginia were surveyed. The bounds of the survey were defined by the size of dissected hollows and spurs for these hillslopes. Surface elevations were recorded at a resolution of 0.5 to 2 m. Catchment areas which were used as a surrogate for runoff concentration were determined using digital elevation models. Results from this study suggest that although some of the measures of runoff concentration could be expressed in terms of slope length and gradient, it is unlikely that complete probability distribution of catchment areas could be derived based simply on slope gradients and lengths.