Risk Assessment for Safe Drinking Water Supplies - Global Drinking Water Management and Conservation - page 115

Table 6.1 Steps involved in a watershed ecological risk assessment framework (USEPA 2007 )
Step 1: Problem formulation
Translate proposed use into a goal and objectives
Develop conceptual model
Identify assessment endpoints and measures of impacts
Step 2: Risk analysis
Evaluate stressors, pathways, and measures of impacts
Use reference conditions and watershed data to determine effects on assessment endpoints
Step 3: Risk characterization
Compare stressor levels and physicochemical regimes with minimum thresholds or criteria for
assessment endpoints
Determine relevant causes of nonattainability; stressor identi cation evaluation
Step 4: Risk management
Identify control options if applicable
Consider feasibility of speci c controls
Conduct stakeholder discussions and management option evaluation
Modify the plan if necessary

Fig. 6.1 Elementary
conceptual model (USEPA
2007 )

As an example, Table 6.2 shows the application of the assessment endpoints to
respond to the stressors in the Waquoit Bay watershed. 1 A scoring approach is
applied to evaluate the priority of stressors in the Waquoit Bay assessment. Pro-
fessional judgment is used to rank the effects of stressors on identi ed assessment

endpoints (Serveiss et al. 2004 ). Through the matrix given in Table 6.2 , the risks
associated with various stressors and their impacts can be estimated in a quantitative
manner. Assessment endpoint can translate environmental management goals into a
measurable system of attributes.

1

See http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=162845 for a further description.