Aspects of Aquatic Ecological Risk in Resource Management and Point Source Control

Generally, ERA, like most risk assessment methodology, is founded on the need to address uncertainty in the decision process. Management decisions regarding the aquatic ecosystem have to deal with both epistemic (knowledge base) uncertainty and innate variability pertaining to both the biotic and abiotic components of the ecosystem. Conventional ERA methodology depends on a statistical approach to address both uncertainty and variability. A case can be made to deal with uncertainty and variability by a possibilistic (fuzzy) rather than a probabilistic approach. Fuzzy ERA requires a formulation and assessment of a) how likely a stressor is expected to impact on the ecosystem (i.e. how likely a specific undesired “event” is) and b) How likely any given level of stressor is expected to occur. The former is an expression of the hazard pertaining to the stressor and when combined with the latter, and expression of risk is obtained.