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Multi-Variable Sensitivity Analysis, Calibration, and Validation of a Field-Scale SWAT Model: Building Stakeholder Trust in Hydrologic and Water Quality Modeling

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASABE. 63(2): 523-539. (doi: 10.13031/trans.13576) @2020
Authors:   Ritesh Karki, Puneet Srivastava, David D. Bosch, Latif Kalin, Jasmeet Lamba, Timothy C. Strickland
Keywords:   Agricultural BMPs, Field-scale SWAT, Multi-variable calibration, SWAT, SWAT-CUP.

Highlights

SWAT can adequately simulate runoff, soil moisture, cotton and peanut yields, and nitrate at field scale.

Muskingum routing and adjusting DIS_STREAM are important to simulate fields as watersheds rather than HRUs.

Crop yield calibration is critical for improving SWAT model robustness in nutrient transport simulations and for building stakeholder trust.

SWAT can quantify the impacts of different management scenarios at the field scale.

Abstract. Multi-variable calibration of a field-scale Soil and Water Assessment (SWAT) model is critical for understanding the true impacts of irrigation and nutrient best management practices (BMPs) on hydrology, water quality, and agricultural productivity and for building stakeholder trust for eventual BMP implementation at the watershed scale. This study evaluated the ability of SWAT to simulate runoff, soil moisture, cotton and peanut yields, and nitrate in conventionally tilled and strip-tilled plots while also evaluating the differences in hydrological and nutrient simulation parameters for the two tillage practices. Modeling results showed that SWAT adequately simulated runoff, soil moisture, cotton and peanut yields, and nitrate at the field scale and that calibrated values for the curve number of operation (CNOP) were different for the conventionally tilled and strip-tilled plots and critical to runoff calibration. It was also important to change the routing method from variable storage to Muskingum and to adjust DIS_STREAM for runoff simulation if the field was to be simulated as a watershed rather than as an HRU. Sequential calibration of surface runoff, soil moisture, crop yield, and nitrate showed that crop yield can be an important consideration for improving SWAT model robustness in nutrient transport simulations. Soil moisture calibration did not have a significant effect on runoff simulations. Evaluation of the impacts of different management scenarios showed that soil moisture sensor-based irrigation, cover crop, and strip tillage had the highest potential for reducing nutrient loss and conserving water while maintaining agricultural productivity in southern Georgia. This study also demonstrated to stakeholders that the SWAT model can successfully quantify the impacts of different management scenarios on their farm fields.

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