Abstract values for problematic substances in waterways cannot be passed on to the public without a framework of reference. Correlating measured values with the legally required threshold values enables compliance with the water protection regulations to be communicated. It is thus easy to evaluate the message conveyed by the indicator (values that exceed the threshold values are negative).

The new formulation will enable the indicator to round out the information provided by E13 to give an overall picture of the way problematic substances are developing in waterways.