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Title: Framework to parameterize and validate APEX to support deployment of the nutrient tracking tool

Author
item Moriasi, Daniel
item King, Kevin
item Bosch, David
item Bjorneberg, David - Dave
item Teet, Stephen
item GUZMAN, JORGE - University Of Illinois
item Williams, Mark

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/4/2016
Publication Date: 7/9/2016
Citation: Moriasi, D.N., King, K.W., Bosch, D.D., Bjorneberg, D.L., Teet, S.B., Guzman, J.A., Williams, M.R. 2016. Framework to parameterize and validate APEX to support deployment of the nutrient tracking tool. Agricultural Water Management. 177:146-164.

Interpretive Summary: The Agricultural Policy Environmental eXtender (APEX) model is the scientific basis for the Nutrient Tracking Tool (NTT). NTT is a user-friendly web-based computer program developed to assist farmers or their technical service providers to estimate reductions in nutrient losses to the environment associated with alternative practices locally. However, the absence of a clearly defined, consistent approach to parameterization has raised questions over the reliability and consistency of simulated results. In this paper, a literature review of current parameterization and validation steps and performance evaluation criteria for APEX was performed. The guidelines for parameterization and validation were then developed based on the literature review findings and personal experience. These guidelines are in the form of recommendations covering essential phases of model simulation studies related to parameterization and validation and include: 1) a clear definition of purpose of study and identification of major processes; 2) proper representation of study site when building a project; 3) description of parameterization and validation approaches including ideal, typical, and minimum required categories; 4) validation of scenario results for NTT; and 5) providing detailed documentation and reporting of all steps and the corresponding essential information. These guidelines are intended to serve as the framework for parameterizing and validating APEX to support nation-wide deployment of NTT and can also be adopted for use in other hydrologic and water quality models.

Technical Abstract: The Agricultural Policy Environmental eXtender (APEX) model is the scientific basis for the Nutrient Tracking Tool (NTT). NTT is an enhanced version of the Nitrogen Trading Tool, a user-friendly web-based computer program originally developed by the USDA. NTT was developed to estimate reductions in nutrient losses to the environment associated with alternative practices. The local-project driven approach has provided the opportunity to demonstrate NTT in locations throughout the country; however, the absence of a clearly defined, consistent approach to parameterization has raised questions over the reliability and consistency of simulated results. The goal of this paper was to develop and present guidelines for parameterization and validation of APEX to support NTT. A literature review of current parameterization and validation steps and performance evaluation criteria for APEX was performed. The guidelines for parameterization and validation were then developed based on the literature review findings and the experience of the authors. These guidelines are in the form of recommendations covering essential phases of model simulation studies related to parameterization and validation and include: 1) a clear definition of purpose of study and identification of major processes; 2) proper representation of study site when building a project; 3) description of parameterization and validation approaches including ideal, typical, and minimum required categories; 4) validation of scenario results for NTT; and 5) providing detailed documentation and reporting of all steps and the corresponding essential information. Overall the resulting guidelines are intended to serve as the framework for parameterizing and validating APEX to support nation-wide deployment of NTT. Additionally, the recommended procedures are general and can be adopted for use in other hydrologic and water quality models.