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ARS Home » Midwest Area » Columbus, Ohio » Soil Drainage Research » Research » Publications at this Location » Publication #253286
Title: Importance of Crop Yield in Calibrating Watershed Water Quality Simulation Tools

Author
item SUJITHKUMAR, SURENDRAN - The Ohio State University
item King, Kevin
item WITTER, JONATHAN - The Ohio State University
item SOHNGEN, BRENT - The Ohio State University
item Fausey, Norman

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2011
Publication Date: 12/1/2011
Citation: Sujithkumar, S., King, K.W., Witter, J.D., Sohngen, B.L., Fausey, N.R. 2011. Importance of crop yield in calibrating watershed water quality simulation tools. Journal of the American Water Resources Association. 47(6):1285-1297.

Interpretive Summary: Natural resource computer models are used to identify gaps in research knowledge, aid in design of hydrologic structures, project the environmental responses of land management practices, and guide water quality policy. Thoroughly calibrating the model prior to application is necessary for attaining high levels of confidence in model predictions. A rigourous four step calibration procedure was outlined and demonstrated for one of the most widely used natural resource simulation models. Following the proposed calibration procedure produced more accurate results compared to using a one phase or two phase calibration approach. Extension educators, design engineers, regulators, and policy makers that rely on accurate natural resource predictions can more confidently predict hydrology and water quality impacts using this calibration procedure.

Technical Abstract: Watershed scale water quality simulation tools provide a convenient and economical means to evaluate the environmental impacts of conservation practices. However, confidence in the simulation tool’s ability to accurately represent and capture the inherent variability of a watershed is dependent upon high quality input data and subsequent calibration. A rigorous calibration procedure is outlined and demonstrated using data from Upper Big Walnut Creek (UBWC) watershed in central Ohio, USA. A four stage iterative calibration process was proposed: 1) parameter selection, 2) hydrology calibration, 3) crop yield calibration, and 4) nutrient loading calibration. Progressive calibration that integrates crop growth and yield predictions with stream flow and nutrient loadings resulted in increased prediction efficiencies for both calibration and validation time periods. Improved efficiencies for stream flow were realized for all temporal scales examined (daily, monthly, and annual). Following the four stage calibration, 10-year stream flow validation prediction efficiencies were 0.5 for daily, 0.85 for monthly, and 0.87 for annual time periods. Prediction efficiencies for crop yields during the validation period were 0.54 for corn 0.69 for soybeans and 0.61 for wheat. Nitrogen loading prediction efficiency was 0.65. Using this four stage calibration procedure will provide a greater level of confidence in the predicted results.