The public and their elected representatives want to see whether they get Value-for-Money from investment in preventing pollution.For many rivers, the achievement of good water quality is a matter of regulating the discharges from wastewater treatment plants. The effective audit of the quality of such discharges is a good basis for measuring progress in controlling pollution.To prove that control is effective, the techniques which underpin the following tasks must be sound and consistent: - the standards for rivers must be devised so that the environmental objectives are met with the required reliability; the form of the standards will be constrained by the procedures available to monitor compliance; - the standards worked out for effluents must have the correct mathematical relation with the river targets, and they too must be consistent with the options available for auditing performance; - the assessment of compliance must be objective; and, - statistics used to summarise the performance of a region (or a Nation) must be simple, stable, clear, and consistent with the results for individual sites.