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HER

Hydro-Ecoregions (HER) - The French way to river typology and the definition of Hydro-Ecoregions (HER)

In order to better understand the rationale of the adopted typology for Italian rivers, some concepts related to the definition of European Hydro-Ecoregions (HER) are here briefly presented. The HER approach is derived from the French experience and was originally developed  by CEMAGREF in order to establish a WFD compliant river typology for France. The approach did involve two levels of analysis:

  • the definition of Hydro-Ecoregions (HER), i.e. areas characterized by a limited variability in chemical, physical and biological features;
  • the definition of river types to be defined within the HER, based on a limited number of variables not included in the definition of HER.

The concept of Hydro-Ecoregion (HER) is derived from the concept of terrestrial ecoregion and focuses on aquatic ecosystems and their characteristics in relation to terrestrial ecosystems. It is based on a top-down approach where control factors regulate local observed conditions in rivers. The natural diversity of the rivers is considered to be the result of a combination of two factors: upstream-downstream gradient and regional heterogeneity, i.e. differences between the HER. The concept is based on theories of hierarchical control of hydro-systems. Main factors defining hydro-systems are geology, topography and climate.     These three drivers regulate morphodynamics and hydrochemical parameters at river reach and, therefore, ecosystem and biotic communities. Geology, topography and climate are considered the main factors shaping water ecosystems at catchment scale. Basic assumptions of Hydro-Ecoregions approach are: a) within each HER, running water ecosystems should have a limited variability for chemical, physical and biological features, as well as a similar pattern of longitudinal variation b) ecosystems from different HER must differ for at least one of the main abiotic parameters and these differences must reflect a consistent and significant effect on the biological structure. The use of a regional based approach (such as HER approach is) does offer significant advantages:

  • ease in the attribution of each river section to a given type
  • automatic allocation options for types throughout the country
  • strong coincidence between HERs and territorial management units
  • good compromise between ecosystem features and management needs
  • integration of some of the descriptors required for WFD system B ensuring simplification of interpretation and full normative compliancy 
  • HERs are a good basis for the definition of type-specific reference conditions.

Furthermore, the use of Hydro-Ecoregions as an intermediate step in the definition of river types ensure high comparability between different parts of Europe (France, UK, Austria etc).
For more details on the approach HER [News December 2006]: http://www.cemagref.fr/le-cemagref/lorganisation/les-centres/lyon/ur-maly/Hydroecologie_Cours_dEau

Main publications (in italian)
Wasson J.W., A. Garcia Bautista, A. Chandesris, H. Pella, D. Armanini & A. Buffagni 2006. Approccio delle Idro-Ecoregioni europee e tipologia fluviale in Francia per la Direttiva Quadro sulle Acque (EC 2000/60). Notiziario dei Metodi Analitici IRSA-CNR 2006 (1): 20-38.