INHABIT project

  • Increase font size
  • Default font size
  • Decrease font size
Home The INHABIT project Environmental problem targeted

Environmental problem targeted

Among the aims of the WFD, preventing deterioration of the status of surface water bodies and protecting, enhancing or restoring surface water bodies is central. More in details, good surface water status should be achieved by 2015. Therefore, for each river basin district, the WFD requires a River Basin Management Plan (RBMP) to be prepared, which must be reviewed every six years. The plan aims at setting out the environmental objectives for all water bodies in the district and presents a summary of the measures that are being used to achieve such objectives.

To derive cost-effective measures and assessing their success, some key points must be considered.

1) The WFD brings Biological Quality Elements to the core of ecological status evaluation. This is quite an innovative approach but leads into additional problems to be managed for effective monitoring and classification. For instance, biological communities show an intrinsic variability, which can affect quality evaluations, whose effects the WFD attempts to limit by introducing a type- or site-specific approach. In other words, to understand what happens at a water body, methods for monitoring must be designed to reduce the influence of natural variability, so that the variation observed in biological communities is correctly attributed to the effects of the pressures acting. To do this, types must be defined in the best possible way and with adequate detail. This will ensure that impact on communities is precisely assessed and catchment management can be cost-effective. This leads to the assumption that more types are better for a successful river management of rivers. Obviously, if a high number of types is derived, catchment management will be more strenuous in terms of resources employed i.e. more ‘reference conditions’ will have to be described and a higher number of water bodies be obtained. Therefore, only major water body types are recognized by typologies, which therefore account for most important differences among types to be removed only and for large-scale constraints to species distribution e.g. biogeographical, regional and longitudinal zonation (for rivers). As a consequence, natural variation of communities within a type will remain potentially high, affecting any quality estimations and evaluation of efficiency of measures in RBMPs.

2) The effect of any errors in monitoring results and information used for classification and data interpretation is more dramatic when allied to the one-out all-out principle, whose adoption is required by the WFD. This is because monitoring results for only one BQE or chemical need to wrongly suggest an impact on the water body in order for it to be assigned a lower class than its ‘true’ class. The probability of placing water bodies wrongly in a lower class than their true class increases as more quality elements are brought into the classification process. Therefore, in many cases the tendency will be to limit to one only BQE the collection of monitoring data, which might not be optimal for a sound WFD implementation. Nonetheless, it is important that this risk of misclassification is managed to reduce the danger of wasting resources on unneeded improvements in ecological status. As a consequence, to avoid competent Authorities will limit to one BQE only WFD operational monitoring, uncertainty in classification should be reduced.

3) Once we exclude the potentially high influence of water pollution, for which management actions are comparatively well known and implemented, physical habitat conditions are the most relevant aspect affecting aquatic taxa presence and distribution. The WFD refers to such habitat conditions under the term ‘hydro-morphology’. According to EC guidances, hydro-morphology is ‘the physical characteristics of the shape, the boundaries and the content of a water body’. In fact, local hydro-morphology e.g. presence, distribution and feature of micro- and meso-habitats, local flow conditions, substrate characteristics and stability, erosional or depositional character of a site, the degree of lake burial, is what defines directly or indirectly overall habitat conditions. Hydraulic and morphological i.e. hydro-morphological features are crucial in structuring the habitats of aquatic organisms in rivers and lakes. The importance of hydraulic conditions at the site scale in influencing freshwater biotic communities is historically recognized by the scientific community and water depth, lake level, residence time, velocity, turbulence, shear stress and flow types are among the major hydraulic parameters affecting biota distribution. As well, channel substrate for rivers and features of riparian and shore zone for lakes obviously affects invertebrates, fish and macrophytes distribution. Not only such habitat aspects will determine presence and distribution of species, but will also finely tune abundance of most taxa, aspect that has to be statutorily considered for WFD monitoring and assessment. Therefore, it is clear how ‘local hydro-morphology’ i.e. habitat should always be considered in the key steps of water body characterization, classification and setting of measures, due to its unquestionable relevancy for BQEs. This will support a reliable interpretation of biotic response to pressures and, therefore, of ecological status classification, simultaneously providing evidence on sources for what is often generically called ‘uncertainty’ in biological results. Such uncertainty can be, to a relevant degree, related to habitat conditions, which can be quantified and taken into account for classification issues and while setting measures to restore/maintain water bodies in a good ecological status.

4) Local hydro-morphology will affect not only BQEs but also nutrients dynamics. For instance, nitrogen and phosphorous removal along the longitudinal river axis mainly depends on the sequence and characteristics of in-stream habitats (i.e. highly relevant for management of point-source pollution). As well, transversal processes in nutrients removal depend on banks features and structure (i.e. highly relevant for management of non point-source pollution). Also, substrate characteristics and organic matter distribution on the local scale i.e. down to the micro-habitat level, can strongly affect microbial activity and nutrients removal. The combination of such factors, along the three spatial dimensions (lateral, vertical and longitudinal), will result in efficient self-depuration or rivers and lakes or not. On turn, this also implies a direct or indirect relation with processes acting in the groundwater zone.
In summary, habitat conditions and local hydro-morphology in rivers and lakes have impressive concern for aquatic ecosystems functioning and, therefore, will affect any methods applied for monitoring and classification, unless their influence on biota and processes is explicitly addressed and quantified. In the overall context presented above, aim of the project is to bring into real WFD world i.e. RBMPs scenarios, habitat-related information, so that biological uncertainty in classification can be assessed, efficiency of existing measures checked and innovative restoration measures proposed for application.