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Bijukshe FINAL 7 14 23 with cert.pdf (4.66 MB)

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Monitoring, Modeling and Implementation of Best Management Practices to Reduce Nutrient Loadings in the Atwood and Tappan Lake Watersheds in Tuscarawas Basin, Ohio

Bijukshe, Shuvra
http://rave.ohiolink.edu/etdc/view?acc_num=ysu1689340221146465

Abstract Details

2023, Master of Science in Engineering, Youngstown State University, Department of Civil/Environmental and Chemical Engineering.
Water quality in lakes and reservoirs has been significantly degraded due to anthropogenic activities including point and non-point source pollution. Agricultural practices, particularly excessive fertilizer application, have been consistently identified as a major contributor to water contamination in the lakes and reservoirs. The escalation of nutrient loading into water bodies has raised serious concerns regarding eutrophication in lakes, as well as the potability of drinking water and other consumptive use of water. In order to address these problems, Best Management Practices (BMPs) have been implemented globally to reduce nutrient loadings and improve water quality in lakes and reservoirs. This study aims to assess the effectiveness of BMPs in reducing nutrient levels in the Atwood and Tappan Lakes of the Tuscarawas basin in Ohio by monitoring the sites for water quality sampling and using the Soil and Water Assessment Tool (SWAT) for watershed modeling. Stream flow data from five USGS gauge stations were gathered for multi-site calibration and validation of the model, whereas water quality data from five representative stations within the watersheds were monitored to calibrate the model for nutrients. The performance of the model for streamflow calibration at various USGS gauging stations was satisfactory with Nash-Sutcliffe Efficiency (NSE) values ranging from 0.54 to 0.79 during calibration, and 0.50 to 0.89 during validation. However, due to limited availability of water quality data, the calibration of nutrient was not as good as hydrological calibration. Subsequently, a scenario analysis was carried out using the calibrated SWAT model to assess the effectiveness of different management practices in reducing nutrient levels from the sub-watersheds. The selection of management practices, such as filter strips, grass waterways, fertilizer reduction, crop rotation, and cover crops, were considered for analysis based on active consultation with local stakeholders involved in nutrient reduction initiatives in each watershed. The analysis encompassed 12 subwatersheds of Atwood Lake and 10 sub-watersheds of Tappan Lake, evaluating the performance of these BMPs in both watersheds. The analysis revealed a remarkable outcome, demonstrating that a synergistic implementation of cover crops (rye), grass waterways, and a 10% reduction in fertilizer usage caused the most substantial reduction in nutrient flow by 88%. On the contrary, only 10% reduction in fertilizer application without the incorporation of other BMPs resulted in a small reduction (9%) of nutrient levels. These results underscore the significance of implementing a comprehensive and integrated approach to effectively combat nutrient pollution while maintaining agricultural productions. The overall analysis suggested that notable reductions in total nitrogen and total phosphorus could be achieved, ranging from 8% to 53% for nitrogen, and from 7% to 88% for phosphorus, depending upon the specific combination of Best Management Practices (BMPs) implemented in the watersheds. The study emphasizes the efficacy of employing grass waterways with cover crop and fertilizer reduction to mitigate nutrient losses in both nitrogen and phosphorus. Since the water quality model was not well calibrated, the comparison of calibrated and uncalibrated was accomplished to report the discrepancy in modeling outcome with less calibrated models. When comparing the efficacies of BMPs with the calibrated and uncalibrated water quality models, the calibrated model demonstrated a slightly higher reduction in nutrient load but not a significant difference in nutrient load reduction compared to the uncalibrated model. Furthermore, when the rankings of BMPs in terms of nutrient load reduction were compared, both the calibrated and uncalibrated models demonstrated a similar pattern and retained their relative effectiveness with a consistent order in terms of rankings despite the absolute changes in overall nutrient reduction levels between the two models. The same order of rankings from both calibrated and uncalibrated models affords credibility to the findings and imply that the relative efficacy of different BMPs in decreasing nutrient loads could be independent of model calibration. Also, the study explored on the significant impact of cattle grazing on nutrient loads within the watersheds. It was observed that allowing cattle to graze freely on pastureland resulted in a substantial increase in total nitrogen and total phosphorus. However, by reducing the grazing rate to 50% and 25%, the model predicted less increment in nutrient levels suggesting the sensitivity of cattle grazing in nutrient loadings from pastureland. The research findings also suggested that the effectiveness of implemented BMPs could rely on the specific characteristics of each site, including the land cover, local land use pattern, and climatic conditions. This study emphasizes the selection and implementation of BMPs are site-specific and the BMP efficacy reported in this study are not simply transferable to other regions rather rely based on the unique land use and land cover characteristics of each area. By adopting the suggested BMPs in this study, significant improvement can be made in curbing nutrient runoff and its detrimental impacts on water quality in the study area. Also, this study underscored the challenges of monitoring and calibrating the SWAT model for nutrients at a small sub-watershed scale. Nonetheless, the findings provide valuable insights for stakeholders involved in the restoration of the Atwood and Tappan Lakes watersheds.
Suresh Sharma, PhD (Advisor)
Sahar Ehsani, PhD (Committee Member)
Peter Kimosop, PhD (Committee Member)
77 p.
Civil Engineering
SWAT Model; Calibration; Validation; Nutrient; Nitrogen; Phosphorus; Stakeholders

Recommended Citations

Citations

  • Bijukshe, S. (2023). Monitoring, Modeling and Implementation of Best Management Practices to Reduce Nutrient Loadings in the Atwood and Tappan Lake Watersheds in Tuscarawas Basin, Ohio [Master's thesis, Youngstown State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1689340221146465

    APA Style (7th edition)

  • Bijukshe, Shuvra. Monitoring, Modeling and Implementation of Best Management Practices to Reduce Nutrient Loadings in the Atwood and Tappan Lake Watersheds in Tuscarawas Basin, Ohio. 2023. Youngstown State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ysu1689340221146465.

    MLA Style (8th edition)

  • Bijukshe, Shuvra. "Monitoring, Modeling and Implementation of Best Management Practices to Reduce Nutrient Loadings in the Atwood and Tappan Lake Watersheds in Tuscarawas Basin, Ohio." Master's thesis, Youngstown State University, 2023. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1689340221146465

    Chicago Manual of Style (17th edition)

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This open access ETD is published by Youngstown State University and OhioLINK.