Effects of uncertainty in hydrologic model calibration on extreme event simulation

Anthony David Roche
2005
Computer models representing the hydrologic cycle as a simplified system have become a preferred tool for estimating floods. However, scientific understanding of the uncertainty inherent in these models has not kept pace with their development and application. In many cases it is incorrectly assumed that all uncertainty in model structure, input data, and parameters is minimized or eliminated through calibration. The end result is a ubiquitous but unknowable degree of model predictive
more » ... y that may or may not significantly affect the outcome of any given application. Extrapolation o f a model beyond its calibration range (i.e., for extreme event simulation) invariably results in a substantial increase in this uncertainty. This work aims to promote qualitative and quantitative understanding of model predictive uncertainty in extreme event simulation. It therefore begins with a review of the many sources contributing to model predictive uncertainty, an analysis of their origins and interdependencies, and a synthesis of various methods for analyzing uncertainty. As a pre-requisite step towards the larger goal of reducing overall model predictive uncertainty, this work investigates the variability in estimates of extreme floods (e.g., peak flow, timing, and volume) introduced by subjective decisions made during calibration. Multiple automatic calibrations of a conceptual hydrologic model are conducted using different objective functions to evaluate calibration performance, resulting in a collection of non-inferior parameter sets. Each parameter set is then used to simulate an extreme event based on hydrologic data for the Coquitlam Lake watershed in British Columbia, which is developed for hydropower by BC Hydro. The combined output of these extreme event simulations characterizes the relative variability in the hydrographs. Simulations are conducted using the University of British Columbia Watershed Model (UBCWM), which is widely used to describe and forecast watershed behaviour in mount [...]
doi:10.14288/1.0063331 fatcat:qf5unna3hnelvofnt5rvtgyymi