Comparisons of the Quantification of Hydro-Climatologic Uncertainties in Recent Risk Assessments Affecting Basin Scale and Global Scale Hydrologic Phenomena

The field of Climatic - Hydrologic Uncertainty Quantification (CHUQ) has a vital history within the various modes of risk assessments to which it has been applied. This paper highlights notable historic examples of CHUQ with regard to their respective strategies in addressing reducible and irreducible uncertainty (IU) towards policy-driven risk assessment goals. The author reviews three past research projects based on his direct participation in two geologic nuclear repository programs. These relate to paleo, current day, and predictive future climatic - hydrologic modeling investigations. Key hydrologic aspects of those projects which address the field of CHUQ are then considered in light what can be inferred concerning IU. Accordingly, the three sample hydrologic cases are compared in ways that highlight and clarify differences in risk assessment goals, hydrogeologic conceptualizations, stochastic and deterministic modalities, data traceability, model validation, model sensitivity, model uncertainty, and alternate conceptual models. For the more quantitative aspects of the evaluations, basic statistical metrics, including variances and root mean squared errors, are produced which summarize the comparisons.