9.4.2 Target criteria

Target criteria (operational objectives) should be set for each operational characteristic included in the monitoring program. The target criteria, which reflect the effectiveness of each process or activity, can be quantitative (numerical), for example, having a turbidity target for post-filter water, or qualitative (descriptive), as in setting acceptable levels of human activity in a catchment or reservoir.

Operational monitoring results are compared with these target criteria to assess if anything unusual is occurring within the water supply system. Any deviation from established targets should be regarded as a trend towards a potential loss of control over the system, and should result in appropriate investigations or corrective actions to ensure control is maintained and/or mitigate potential problems.

For some operational monitoring, particularly that undertaken upstream of treatment, target criteria and objectives for characteristics are often based on a more subjective assessment of what is considered normal or acceptable in the light of the water system analysis / risk assessment process (e.g. E. coli numbers in feeder streams and raw water). Monitoring of these characteristics provides an indication of changes from background levels that may influence the reliability of the original estimated challenge and consequently, the adequacy of subsequent downstream processes. The long-term review of monitoring results provides an opportunity to validate these criteria, and adjust preventive measures and associated criteria as required.