Investigating Explicit and Implicit Decisions of Modelers Across Three Watershed Models

Abstract:

Scientists utilize watershed modeling tools as a way to better understand and combat nutrient pollution on a large scale. Chesapeake Assessment Scenario Tool (CAST), SPARROW (SPAtially Referenced Regression On Watershed attributes), and Soil & Water Assessment Tool (SWAT) are modeling tools that allow for the simulation of nutrient loads in the Chesapeake Bay Watershed (CBW). Scientists, like all humans, make both explicit and implicit decisions guided by values, beliefs, and principles in everyday life including in their daily research activities. Explicit modeling decisions are often articulated in journal and conference papers, although implicit decisions driven by value judgements are typically ignored or under prioritized in scientific discourse.

The influence of these decisions on modeling tools has been investigated in climate change modeling, however, these theories have not been applied to watershed science modeling. The purpose of this study is to investigate both ethical and epistemic choices regarding the three aforementioned watershed models. The research question guiding this study is, “What are the preferences, values, and beliefs that influence a scientist’s decision to select a particular watershed model over another watershed model?” We hypothesize that the primary users of SWAT, CAST and SPARROW will be most influenced by the popularity of a model among their peers and access to the model by their workplace when describing model choice. We also expect to uncover a variety of values choices laden within and across the three watershed models. To answer this question, we will utilize both an online survey and expert interviews. The survey results will highlight scientist preferences and will utilize factor analysis to associate correlation between a subset of variables. During interviews, ethical concepts relating to value choices associated with modeling efforts will be elicited. These results will be analyzed using a qualitative process where ethical and epistemic concepts will be coded using a Values Informed Mental Model framework. The goal of this research is to provide insight into the tradeoffs associated with assumptions within these models, so that modelers can make an informed decision before generating nutrient loading forecasts to guide watershed policy decisions for the CBW.