Evaluating the Scalability of a Process-Consistent Hydrologic Model

English Abstract:

Hydrologic models often fail to generate simulations that are consistent with internal watershed processes, despite commonly being able to match streamflow dynamics (following calibration). This shortcoming is particularly attributed to simple, conceptual models due to a lack of physical realism. At the same time, hydrologic model simulations are confronted with complications caused by a potential shifting of dominant processes with scale. In this study, we explore the scalability, sensitivity, and transferability of the parameters of the Catchment Connectivity Model (CCM). The CCM was developed following a dominant process conceptualization based on empirical hillslope hydrologic connectivity observations at the Tenderfoot Creek Experimental Forest (TCEF; Montana, USA). The three-parameter CCM is a spatially explicit model structure that has been validated against extensive field observations of hillslope hydrologic connectivity (an internal process simulated by the model) to demonstrate its internal consistency, in addition to a traditional assessment to the external streamflow dynamics. Specifically, we explored the variation in model parameterization across multiple scales across seven nested TCEF watersheds. A diagnostic model calibration analysis was considered where the role of a priori parameter ranges was explored in relation to both external (streamflow) and internal (hydrologic connectivity) model performance. This investigation allowed us to develop a more in-depth understanding of the model structure, its scalability, its sensitivity, and its transferability from one watershed to the next.