Browsing by Author "McClellan, P. W."
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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.
- Effects of forest harvesting best management practices on surface water quality in the Virginia coastal plainThompson, Theresa M.; Mostaghimi, Saied; Frazee, J. W.; McClellan, P. W.; Shaffer, R. M.; Aust, W. Michael (American Society of Agricultural and Biological Engineers, 2000)Three small watersheds located in Westmoreland County, Virginia, were monitored to evaluate the impact of forest clearcutting on surface water quality and to evaluate the effectiveness of forestry best management practices (BMPs) for minimizing hydrologic and water quality impacts associated with timber harvesting. One watershed (7.9 ha) was clearcut without implementation of BMPs, one watershed (8.5 ha) was clearcut with the implementation of BMPs and a third watershed (9.8 ha) was left undisturbed as a control Forest clearcutting without BMP implementation reduced storm runoff volume and did not significantly change peak flow rates. Following site preparation, both storm flow volumes and peak flow rates decreased significantly. For the watershed with BMP implementation, storm flow volume decreased significantly following harvest, while peakflow increased. Site preparation did not change storm flow volumes over post-harvest conditions, bur did significantly reduce storm peak flow rates. Disruptions in subsurface flow pathways during harvest or rapid growth of understory vegetation following harvest could have caused these hydrologic changes. Harvest and site preparation activities significantly increased the loss of sediment and nutrients during storm events, Storm event concentrations and loadings of sediment, nitrogen, and phosphorus increased significantly following forest clearcutting and site preparation of the No-BMP watershed. Both the BMP watershed and the Control watershed showed few changes in pollutant storm concentrations or loadings throughout the study. Results of this study indicate forest clearcutting and site preparation without BMPs can cause significant increases in sediment and nutrient concentrations and loadings in the Virginia Coastal Plain. However these impacts can be greatly reduced by implementing a system of BMPs on the watershed during harvesting activities.
- Factors Influencing the Amount of Time Spent By Cattle In Streams: Implications for TMDL DevelopmentMasters, Amanda Lynn (Virginia Tech, 2002-07-08)The amount of time cattle spend standing in streams is one input parameter needed by computer models when total maximum daily load (TMDL) plans are being developed. This input parameter is estimated using professionals' best judgment because experimental data are not available, and estimations are generally inconsistent. The goal of this study was to gain a better estimate of the amount of time cows spend in streams, since this has a significant impact on direct fecal coliform loadings to streams. Significant factors influencing the amount of time cattle spend in streams were identified, and a relationship was developed for predicting the amounts of time cattle spend in streams. Five farms were studied in southwest Virginia from August 2001 through February 2002. Camera surveillance systems were set up on two beef farms and three dairy heifer operations, and cattle activity in streams was recorded during daylight hours. Climatic data, pasture characteristics, feed characteristics, and farm management practices were collected from each site, and their relationships with the amount of time cattle spend in streams were investigated. No significant difference (p=0.82) was found between the amount of time beef cattle and dairy heifers spent in streams. Overall, cows spent an average of 10.12 min day-1cow-1 standing in streams during the observation period. Throughout the study period from August to February, cows spent the highest amount of time in streams during the month of November (14.3 min day-1cow-1). Feed, climatic, and pasture parameters were found to influence the amount of time cattle spent in streams. These significant parameters were used to develop an empirical equation for predicting cattle presence in streams. This model may not accurately predict the amount of time spent in streams by cows during warmer summer months, since data was collected during fall and winter months. Other limitations may be encountered when using the model to predict the amount of time lactating dairy cows spend in streams when streams are their sole water source, since they have a much higher water requirement than those cows studied.
- Impact of agrichemical facility best management practices on runoff water qualityShukla, S.; Mostaghimi, Saied; Lovern, S. B.; McClellan, P. W. (American Society of Agricultural and Biological Engineers, 2001)Water quality effects of structural and managerial BMPs implemented at an agrichemical mixing and handling facility, located in an agricultural watershed in Virginia, were investigated in this study. The measured water quality parameters include two commonly used pesticides (atrazine and metolachlor), nitrogen (N), and phosphorus (P). BMPs implemented include: pesticide mixing and loading concrete pad with a sump and pump fitting; a variety of runoff diversion structures to divert the rooftop runoff away from the critical areas; structures to contain transport of chemicals to the drainage leaving the facility; and recycling of rinsate by applying it on the agricultural land. Concentration of pesticides and nutrients were measured at the facility outlet as well as the outlet of the main watershed in which the facility was located. Implementation of BMPs resulted in drastic reduction in mean concentrations of the two pesticides in the stream leaving the facility as well as in the main watershed stream. Maximum atrazine concentrations in the drainage leaving the facility reduced from 17,389 mug/l during the pre-BMP period (1986-1988) to 1,452 mug/l during the post-BMP period (1989-1996). The post-BMP mean concentrations of atrazine and metolachlor at the facility outlet were reduced by 94% (2690 mug/l to 166 mug/l) and 91% (4579 mug/l to 402 mug/l), respectively. The corresponding post-BMP reductions in concentration at the main watershed outlet were 52% and 78% for atrazine and metolachlor, respectively. Nonparametric trend tests results indicated statistically significant downward trend and reduced post-BMP concentrations of the two pesticides at the facility as well as the watershed outlets. Impact of BMPs on the nutrient concentrations were not clear due to large nutrient contributions from animal production activities in upland areas of the watershed Results from this study will provide needed impetus for implementation of BMPs at other agrichemical mixing and handling facilities in Virginia as well as other states to drastically reduce the transport of pesticides and nutrients to surface water bodies.
- Methods for Measuring and Assessing Nonpoint Source Pollutant Control at a Regional Stormwater Management FacilityKibler, David F.; Mostaghimi, Saied; Lovern, Sharla Benjamin; Karch, E.; McClellan, P. W.; Voshell, J. Reese Jr. (Virginia Water Resources Research Center, 1998-12)This report summarizes work completed on the installation of water quality monitoring equipment and the assessment of initial baseline conditions at the Virginia Tech Regional Stormwater Facility located on the main campus in Blacksburg, Virginia. The long-term goal of the research is to assess the pollutant removal efficiency of the regional stormwater facility,consisting of an upper wet pond and a lower dry pond in series. It was constructed in September 1997. Results collected thus far indicate that the biological condition of the pond area was impaired prior to the construction disturbance at the site and remained so after construction. There is evidence of excessive sedimentation during construction and in the post-construction period. However, there is also some limited evidence that the biological condition in the lower ponding area is beginning to recover, although this is expected to take place at a very slow rate. Again, severe sedimentation and the delivery of attached pollutants is the primary cause of degradation. At this time, all four water quality samplers and flow stations have been installed at the regional pond facility and a complete weather station has been built atop the lower pond dam. The collection and analysis of longer-term data on pond performance can now begin.