10.3 Assessing performance: long-term evaluation of monitoring

The systematic review of monitoring results over an extended period of time (typically 12 months) is necessary to evaluate whether existing system management practices are effective in reducing risk, and to identify opportunities for improvement. The long-term evaluation of performance provides an essential feedback loop and comparison to the hazard identification and risk assessment process, and assists in corroborating or modifying assumptions and increasing system knowledge (see Figures 9.1 and 9.2).

The long-term evaluation of microbial, health-based chemical and aesthetic performance includes the assessment of all available monitoring information from catchment to consumer, including observational activities. The assessment should compare the monitoring information against objectives and criteria, such as guideline values, the microbial health-based targets or agreed levels of service.

Mechanisms should be developed for the long-term evaluation of microbial, health-based chemical and aesthetic performance. Useful tools to facilitate analysis of data sets include graphs, trend charts and, where appropriate, statistical evaluation.

The results from the long-term evaluation of performance should form an input to the senior management review (see Element 11 of the Framework, Section 3.11). Some aspects will be reported externally to consumers, stakeholders and relevant health authorities or drinking water regulators in accordance with requirements. It is an important due-diligence function that provides assurance that data are reviewed regularly and improvements are made in response to identified problems. Such assurance contributes to consumer and stakeholder confidence in the quality of the water being supplied and the actions being taken to manage the water supply system proactively.