Date of Graduation

12-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Biological and Agricultural Engineering

Advisor

Dharmendra Saraswat

Committee Member

Andrew N. Sharpley

Second Committee Member

Rodney D. Williams

Third Committee Member

Michele L. Reba

Fourth Committee Member

Xuan Shi

Fifth Committee Member

Thomas A. Costello

Abstract

For the first objective, predicted impacts of selected Mississippi River Basin Initiative (MRBI) conservation practices (CPs) on sediment and nutrient loss were assessed. The study area was L’Anguille River Watershed (LRW), a priority focus watershed of the MRBI program and the simulated CPs were filter strip, critical area planting, grade stabilization structure, irrigation land leveling, irrigation pipeline, irrigation water management, and nutrient management. The Soil and Water Assessment Tool (SWAT) model was calibrated (1998 – 2005) and validated (2006 – 2012) for flow, sediment, total phosphorus (TP), and nitrate-nitrogen (NO3-N) at the Colt site (503 sq. km. drainage area) and for total flow, surface flow, and base flow at the Palestine site (784 sq. km. drainage area). The statistical results for the calibration and validation were found to be satisfactory or better except a few root mean square error – standard deviations ratio (RSR) values for the calibration period. The SWAT model results were predicted from 2013 – 2017 for assessing the performance of CPs. Out of the CPs used in the LRW, critical area planting was the most effective in reducing the predicted nutrient (58% TP and 16% total nitrogen (TN)) and sediment (80%) loads, followed by filter strip, irrigation land leveling, grade stabilization structure, irrigation pipeline, irrigation water management, and nutrient management. Results such as these could help inform watershed planners and policy makers in selecting appropriate CPs that will most effectively bring about desired nutrient and sediment load reductions.

For the second objective, a CP tool was developed with Python programming language for integrating a user-defined target area utilizing either a single or multiple selection criteria with the SWAT model. The tool uses open source packages such as Geospatial Data Abstraction Library (GDAL) and Matplotlib. The tool is standalone and was designed in such a way that it simulates CPs at the lowest simulation level (hydrological response unit) of the SWAT model by building a new targeting procedure for SWAT applications and decision-making. The tool automates the process for simulating CPs on a target area and analyzing differences between the baseline and CP scenario. The tool was evaluated for the Cache River Watershed (CRW). A target area was selected in the CRW and irrigation land leveling CP was simulated. A 22% decrease in sediment losses, 20% decrease in TP losses, and 12% decrease in TN losses were predicted. The tool provides a quick approach to address the water quality impacts on a specific target area.

For the third objective, the Python-based CP tool developed for objective 2 was further updated to simulate CPs at user-defined locations using an interactive simulation approach. The tool allows the user to select the target area with mouse-clicks in a user-friendly and interactive environment. The LRW located in northeastern Arkansas was used as the test area. A target area was selected interactively in LRW and filter strip and irrigation land leveling CPs were simulated. A 70% decrease in sediment losses, 68% decrease in TP losses, and 47% decrease in TN losses were predicted.

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