Rivers – Reference sites validation

INHABIT project

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Rivers – Reference sites validation

The procedure for reference sites verification, according to Italian legislation, 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 has to 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 not, the site cannot be considered as reference. If more 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. 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.
The document IRSA-CNR Notiziario dei Metodi Analitici, Numero speciale 2008 (in Italian) contains more specific information on reference conditions.
According to reference sites validation performed in INHABIT, all potential reference sites considered in the project has been confirmed. Namely, 2 reference sites have been confirmed in Piedmont HER 6 (Po plains) and 4 in Piedmont HER 1 (Western Alps). In Sardinia an overall number of 16 reference sites has been confirmed, including both sites directly investigated in INHABIT Project and in previous research projects (i.e. MICARI).