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Shedekar Dissertation Dec012016.pdf (5.88 MB)

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Developing an integrated, multi-scale modeling system for assessing conservation benefits in subsurface drained watersheds

Shedekar, Vinayak Shamrao
http://orcid.org/0000-0003-2028-2108
http://rave.ohiolink.edu/etdc/view?acc_num=osu1480606965301556

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Food, Agricultural and Biological Engineering.
An integrated modeling framework was developed by linking the relevant features of DRAINMOD-NII, a field scale hydrologic simulation model with SWAT-2005, a watershed scale simulation model. The uncertainty associated with rainfall measurements as an input parameter common to field as well as watershed scale modeling was assessed by conducting static and dynamic calibration of three tipping bucket raingauge models. Rainfall data measured in a subwatershed (B) of the Upper Big Walnut Creek were then corrected using the calibration equations. A sensitivity analysis using uncorrected versus corrected rainfall data showed significant potential biases in model predictions due to errors in rainfall measurements. The second phase of study involved calibration and validation of DRAINMOD-NII for drainage discharge and nitrate (NO3-N) loads from two subsurface drained fields monitored within the watershed-B. DRAINMOD-NII predicted the monthly, seasonal and annual hydrology and NO3-N loads with good accuracy. Effects of drainage water management (DWM) on annual water and NO3-N budgets were predicted fairly well. However, the hydraulic interdependence of the two fields may have affected the nutrient balance, and hence the estimates of reductions. In the third phase, SWAT-2005 was used to simulate hydrology and nitrogen transport at watershed scale. Overall, SWAT significantly under-estimated the stream discharges at daily, monthly and annual scales. The model performance was relatively better for monthly simulations (NSE of 0.64 and R2 value of 0.67). The total watershed yield on annual basis predicted by the model showed a systematic under-estimation, especially during winter and spring months. Nitrate load simulations by SWAT were unsatisfactory at daily, monthly, as well as annual basis (negative NSE values and slope values close to zero). The nitrate loads and concentrations were several folds lower than those observed during the study period. The errors in simulation of nitrate loading were primarily due to the under-estimation of watershed yield, and also likely due to the combined uncertainty associated with management inputs. Overall, SWAT-2005 posed some major limitations for modeling agricultural watersheds dominated by subsurface drainage. The final phase of study involved integrating DRAINMOD-NII with SWAT-2005 in order to facilitate better representation of field-scale processes and management within the watershed. The integrated model helped improve the sub-watershed scale prediction accuracy of SWAT with respect to daily, monthly and annual drainage discharges and nitrate loads. The improvements in drainage discharges were more prominent during wet years than during dryer years. The integrated framework was able to predict more realistic magnitudes and variations of daily, monthly and annual drainage outflows. The nitrate flows were predicted with a greater accuracy by the integrated model, compared to those by SWAT-based approach. The integrated framework may be further used to evaluate the effects of implementation field-scale management practices, such as DWM, sub-irrigation, and waste-water application.
Larry Brown (Advisor)
Kevin King (Committee Member)
Alfred B.O. Soboyejo (Committee Member)
Khandakar Rafiq Islam (Committee Member)
Norman Fausey (Committee Member)
322 p.
Agricultural Engineering; Environmental Studies; Hydrology; Soil Sciences; Water Resource Management
DRAINMOD, SWAT, Drainage Water Management, Raingauge calibration, Hydrologic Modeling, Watershed, Water Quality

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Citations

  • Shedekar, V. S. (2016). Developing an integrated, multi-scale modeling system for assessing conservation benefits in subsurface drained watersheds [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480606965301556

    APA Style (7th edition)

  • Shedekar, Vinayak. Developing an integrated, multi-scale modeling system for assessing conservation benefits in subsurface drained watersheds. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1480606965301556.

    MLA Style (8th edition)

  • Shedekar, Vinayak. "Developing an integrated, multi-scale modeling system for assessing conservation benefits in subsurface drained watersheds." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1480606965301556

    Chicago Manual of Style (17th edition)

osu1480606965301556
570
© 2016, some rights reserved.Creative Commons License Developing an integrated, multi-scale modeling system for assessing conservation benefits in subsurface drained watersheds by Vinayak Shamrao Shedekar is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by The Ohio State University and OhioLINK.