Reference conditions

CNR-IRSA activities related to INHABIT

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Reference conditions

According to WFD indications the selection and testing of reference sites is a key step in all the processes involving a comparison between observed and expected conditions. At national level in Italy criteria for reference sites verification has been established within a dedicated working group coordinated by MATTM (Ministry of Environment, Territory and Sea Protection). Verification criteria are described in details in Notiziario IRSA-CNR, Numero speciale 2008 (in Italian) and have been subsequently included in the national legislation (DM 56/2009). At the moment the process is in progress, with a first phase completed in several regions of the country.
The National procedure for the validation of river reference sites  consists in a set of questions or ‘criteria’ to be addressed. Questions are related to pressures acting on sites at different spatial scale and are organized in a table (‘check table’). Validation process consists in the completion of the check table that includes 57 criteria, dedicated to the quantification of a specific anthropic pressure. To each criterion a different weight is assigned according to its relevance: Necessary (IR: weight 1), Important (IM: weight 0.6) and Ancillary (AC: weight 0.2). To each criterion a reference threshold and a rejection threshold are set.
The first step of the testing process must assess if:

  • more than 2 IR criteria fall above the rejection threshold
  • more than 4 IR criteria fall above the reference threshold
  • more than 3 IM criteria fall above the rejection threshold
  • more than 6 IM criteria fall above the reference threshold.

If one or more of the four statements above are met, then the site cannot be considered as reference. If more than one criteria fall above any threshold, then the maximum allowed is 6 criteria above any threshold or 3 criteria above rejection threshold.
A score of 1, 0.5 or 0 is then assigned to each question if it falls, respectively, below the reference threshold, between the reference and the rejection threshold or above the rejection threshold. The assigned score is then multiplied by the relative weight. According to the type of alteration identified the questions are distinguished in 7 categories: Point source pollution (score A); Diffuse source pollution (score B); Riparian vegetation (score C); Morphological alterations (score D); Hydrological alterations (score E and F); Biological pressures (score G); Other pressures (score H). Partial scores obtained by summing up the questions within the same category are divided by the maximum possible score within that category. Scores obtained from the single category are then mediated (weighted mean considering the number of questions per category) to obtain the final score. The total score of 0.9 is set as threshold for rejection.