How do you define a good state

The assessment of the water status

With the EU Water Framework Directive, the system of water assessment was fundamentally changed. Previously, the assessment assessed the effects of material discharges into the water and was presented in four quality classes.
In contrast, the entire ecological and chemical status of a body of water is now assessed. For this purpose, a state is first described in which a body of water would be without any significant human impact. This condition is referred to as "very good condition". Depending on how far a body of water has been changed by human influences, it is assigned to four further status classes from "good" to "moderate" to "unsatisfactory" or "bad". The EU Water Framework Directive stipulates that all bodies of water should at least achieve a good status and that no existing status may be deteriorated.

The determination of the ecological status is based on various so-called quality elements. These are fish, invertebrates (e.g. insect larvae or worms), algae and aquatic plants, but also the water balance or the construction of bodies of water. These are either examined directly in a water section or the results of such studies are transferred to water sections that are comparable with regard to the water type and the existing pollution. The deciding factor for the overall assessment is the worst quality element, with the water balance or construction only being decisive for the very good condition.

Significantly modified water bodies
Some surface water bodies have already been changed so much by humans that a good ecological status could only be achieved if measures are taken that "would have significant negative effects on the environment or on certain uses such as energy generation or flood protection". If in these cases alternatives are technically not feasible or would result in disproportionately high costs, the EU Water Framework Directive provides for these water bodies to be designated as "heavily modified water bodies". The target status is then no longer the good ecological status but the good ecological potential. This is not determined on the basis of the biological quality elements but is defined by measures. Put simply, these are structural measures that can be implemented with reasonable effort and that bring about an ecological improvement without significantly impairing the existing use. This exception clause refers exclusively to structural changes such as damming, but not to changes due to water discharge or material inputs.
The assessment methods are described in detail in the Water Information System Austria (WISA). Various guidelines are also available there.

Additional information