Choosing a Model for Your Watershed Modeling Project with BASINS 3.0

The Better Assessment Science Integrating point and Nonpoint Sources (BASINS) system, developed by the U.S. EPA, uses a geographic information system (GIS) framework to integrate national environmental databases with data management utilities, reporting and assessment tools, and watershed and water quality models. The BASINS System can be used to address the technical aspects of a number of EPA regulatory programs, including: TMDLs, NPDES stormwater permitting, watershed management planning, watershed modeling over a range of scales and number of pollutants, monitoring program design, and land use planning. This paper is designed to illustrate to watershed engineers and managers how to best select a model from the suite of models in BASINS for a specific set of watershed conditions and problems. We will outline a decision process that focuses on defining the requirements of the modeling project in light of typical project constraints such as deadline or budget, for use in conjunction with the detailed model analysis in the paper. The remainder of the paper will compare and contrast characteristics of the model considered important in model selection. The set of issues/factors to be discussed include: domain and scale of application; outputs and their relationship to water quality monitoring parameters; necessity and/or benefits of calibration; input data needs and relationship to measurable environmental quantities; associated tools to improve usability such as interfaces and data management and post-processing utilities; modeling approach/ model type including representation of key environmental processes; ability to simulate control scenarios and relation to input parameters; and tradeoffs between accuracy/certainty and application cost. Since advantage and disadvantages are typically in the eye of the modeler, and likely depend on the specifics of the application and requirements of the problem/situation, this paper is designed to provide an open-ended process, and accompanying data, to assist in selecting a model for your own watershed project.