WFD Ecological flows: Using Art. 5 information for the gap analysis (AT)

WFD Ecological flows: Using Art. 5 information for the gap analysis (AT)

Executive summary

For pressure and impact analysis Austria first of all defined the main typical pressures which are impacting the hydrological regime: water abstraction, impounding/ damming, water storage/hydropeaking, (river regulation/channelization). Their relevant “impact” parameters which had proven to be most important for the biological elements are alterations of quantity of flow, saisonal flow dynamics, daily flow fluctuations, flow velocity, water depth /wetted area. These parameter are seen as the relevant ones for eflow definition. In a first rough estimation a panel of experts set values for the parameters mentioned above which would ensure good ecological status for the biological elements with very high confidence and which would mean a failure of GES in any case. In the 1st pressure and impact analysis 2004 information was collected on the main pressures and pressure parameters mentioned above to define water bodies “not at risk”, “at risk” and “possibly at risk”. This also allowed to design the monitoring programme in a most efficient and cost-effective way. In preparing the 1st river basin management plans the biological monitoring results were compared to the environmental objective GES (GAP Analysis).

Austria in the meantime had developed biological assessment methods with specific metrics which are sensitive to hydrological and morphological alterations in addition to metric sensitive to physic- chemical impacts. Guide values for the eflow parameters (quantity of flow, seasonal flow dynamics, daily flow fluctuations, flow velocity, water depth /wetted area) were set for GES for all water body types, limit values for high status.

In the GAP analysis first of all water bodies are checked whether “good biological status” is failed. In case of a failure the next step is to compare the results for the different metrics to find out whether they indicate a hydrological, a morphological or a physic-chemical impact. In case that the hydromorphology sensitive metrics are responsible for a classification worse than good ecological status the hydromorphological information/data of the pressure & impact analysis are used to clarify the reason for failing good status and to carve out the responsible hydrological alteration. This type of procedure in Austria ensures the identification of the water use(r) causing the failure of GES, the designation of tailor-made and cost effective technical restoration programmes. It also ensures basic information/data needed for the Art. 4(3) test, the objective setting / application of exemptions acc. to WFD Art. 4(4) and 4(5).

For the 2nd pressure an impact analysis the values for the hydrological pressure/impact parameters were refined taking into account the limit/guide values set for HES and GES in the National Ordinance on Ecological Quality Objectives – Water Status Assessment. 

General information

Member State(s): Austria
RBD(s): Danube (AT1000), Rhine (AT2000), Elbe (AT5000) Location: nationwide
Time period (start/end): 

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The full case study is available at: https://circabc.europa.eu/w/browse/764dcfed-6e09-4683-be61-951647df760a 

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