of hydro-morphological improvement targets for surface water bodies
Background to research
One of the aims of the Water Framework Directive (WFD) is to achieve ‘good ecological status’in all surface water bodies by 2015 and also to prevent deterioration in the status of these water bodies. This project concentrates on water bodies which may be at risk of failing to achieve good ecological status due to man-induced hydro-morphological pressures and, as a result, theworks may have to be carried out to remove or mitigate those pressures.
The classification of the ecological status of a surface water body is based on: biological elements, hydro-morphological elements supporting the biological elements and chemical and physico-chemical elements supporting the biological elements. The hydro-morphological quality elements must be taken into account when assigning water bodies to the high ecological class and the maximum ecological potential class. For other status/potential classes, the hydro-morphological elements are required to have 'conditions consistent with the achievement of the values specified for the biological elements’. Thus the assignment of water bodies to the good, moderate, poor or bad status/ecological potential classes may be made on the basis of the monitoring results for the biological quality elements. This is because, if the biological quality elements relevant to good, moderate, poor or bad status/potential are achieved then, by definition, the condition of the hydro-morphological quality elements must be consistent with that achievement and would not affect the classification of the ecological status/potential.
For the purposes of the WFD the categories of surface water bodies are: rivers, lakes, transitional waters and coastal waters. If water bodies are seen to be at risk of failing environmental objectives, actions have to be taken by 2015 to ensure that they meet the appropriate standards. In this report these actions are referred to as ‘measures’ or ‘programmes of measures’.
the implementation of the WFD, guidance documents have been prepared on
analysis of pressure and impacts within the characterisation of water
(Guidance for the analysis of Pressures and Impacts in accordance with
2003 and Analysis of Pressures and Impacts, 2003). This
already been carried out for Scotland (SEPA, 2005). That study reviewed
following pressures and assessed their impacts on water bodies:
The present project is concerned with water bodies that are considered to be at risk of failing to achieve good ecological status due to hydro-morphological pressures and the measures that may need to be taken to mitigate these pressures.
The objective of the project was to identify the potential restoration and mitigation targets which could be achieved to meet the requirements of the Water Framework Directive (WFD).
This project reviewed the water resource and morphological risk assessment preliminary results and identified what potential restoration targets may be achievable when assessing improvement measures for those water bodies that are seen to be at risk of failing environmental objectives as a result of significant hydro-morphological pressures. The project assessed potential mitigation measures required to achieve good ecological status. The project assessed potential costs of carrying out the proposed measures.
findings and recommendations
Key words: Water Framework Directive; Hydro-morphology; Surface waters, Rivers, Lakes, Transitional waters, Coasts
This project is concerned with the measures that will need to be taken for water bodies that are considered to be at risk of failing to achieve good ecological status or good ecological potential due to hydro-morphological pressures. SEPA has already carried out a study of the Pressures and Impacts on Scotland’s Water Environment (SEPA, 2005). The results of that study have been reviewed as part of the present project. There was general support, from the project, for the earlier review that had been carried out. The Pressures and Impacts Study identified water bodies that are at risk of failing to achieve Good Ecological Status (GES) due to the presence of one or more pressures. It is possible, however, that when each water body is considered in further detail, a number of these water bodies will be considered to be achieving GES, despite the presence of the pressures. For these water bodies no action will be required to mitigate or remove the pressures for the water body to achieve GES.
project has detailed potential measures that may be carried out to
remove the identified hydro-morphological pressures. These measures
assessed in terms of:
A literature review has been carried out to identify evidence for the impact of the proposed measures. This showed that much of the scientific work that has been carried out relates measures to their impact on the river morphology but there are very few studies which relate measures to their impact on the ecology. For some measures there is scientific support for the impact on ecology but the impact of other measures have not been studied and so there is no underpinning scientific support for these measures. This may reflect the lack of research in these areas rather than suggest that these measures are ineffective.
A series of field visits to selected sites were carried out to validate the measures that had been proposed to address the identified pressures. These site visits confirmed that the proposed measures were appropriate. The field visits also confirmed that some water bodies that have been identified as being at risk of failure to achieve GES due to hydro-morphological pressures may still be achieving good ecological status.
The time scales for achieving ecological improvement is also of importance. In some systems there may be a significant time between measures being carried out and the impact on the hydro-morphology being fully achieved. This delay may depend upon the nature of the measure and upon the nature of the water body. Once the hydro-morphological improvement has been achieved there may be a further delay before there are changes in the ecological system. Thus, it may take a significant period of time before Good Ecological Status is achieved.
The project has developed a procedure for assessing the likely costs of implementing the measures. For each measure a ‘unit’ cost has been derived which is normally expressed as a cost per metre or per square metre of water body. These unit costs have been derived from published data or the experience of project team members.
The water bodies considered where those that were thought to be potentially at risk of failing to achieve Good Ecological Status, excluding Heavily Modified Water Bodies, Artificial Water Bodies and those pressures that may fall under Q and S III. Using the unit costs, the cost of addressing the identified pressures for all the above water bodies has been estimated.
Costs have been estimated on the basis of an average cost for each measure taking into account the potential size of the water body and the length or area affected. In reality the costs for particular locations will vary widely depending upon the particular circumstances. The estimated cost reflects an estimate of the average cost averaged over a large number of sites. Thus the unit costs should not be used to assess the costs for individual schemes, which may be larger or smaller. Where a number of measures may be used to address a particular pressure an assessment has been made of the relative mix of different types of work based on experience and published data. To determine the overall costs, the costs for each water body were then summed to determine the total cost for each water body. This data is presented separately in a series of spreadsheets.
A number of the hydro-morphological pressures may cause water bodies to fail to meet good ecological status arise from current agricultural practises, such as, intensive land use adjacent to the water body. It may be that the measures required the remove or mitigate these pressures will not have to be funded and carried out by SEPA but may be addressed by others, such as the local landowner. To motivate others to do such work, however, SEPA may need to embark on suitable programmes of education and training. If SEPA wish to adopt this approach then it is recommended that an allowance should be made for the costs of providing suitable education and training programmes.
To implement the requirements of the WFD there will be a need for setting targets andmonitoring with respect to hydro-morphological pressures. The problems of doing this are discussed and recommendations made. Using an assessment of habitat is based on the belief that habitat sets the context for the biological communities and that the physical habitat sets the framework for ecological systems. There are a number of existing methods based on an assessment of the geomorphic character of a river or stream, for example, geomorphic River Styles and the Rosgen classification. In addition there are methods which directly address the physical nature of the habitat, such as the US EPA method HABSCORE and the River Habitat Survey (RHS). These are based on the assumption that the quality and quantity of available physical habitat has a direct influence on the biotic community. At present the understanding of the linkages between ecology and geomorphology for water bodies within Scotland does not seem to be sufficient to support methods which concentrate on geomorphology, such as Geomorphic River Styles or Rosgen. There is not the evidence, however, to suggest that methods that are based on detailed surveys of biological communities, such as RIVPACS, take sufficient account of the physical influences. This tends to support that use of methods such as HABSCORE or RHS. A recently approved CEN standard on river hydromorphology (EN 14614) has been developed to enable surveys of rivers to be carried out using a common set of features in Europe. The RHS approach conforms to this standard. This system may offer potential for use by SEPA.
An existing approach to setting targets for rivers is provided by the River Habitat Objectives(RHOs), which are based on the premise that improvements in river habitats will produce ecological benefits.
It must be recognised that setting well-informed habitat objectives requires a good information base. To set targets one needs a method to assess what habitat character is required to achieve Good Ecological Status. The use of RHS cluster analysis provides a means of achieving this.
In the future there will be a need to assess if measures that have been implemented have been successful in improving the ecological status of a water body. For rivers the RHO approach may provide a quantifiable means of achieving this through the use of the River Habitat Quality scores.
Account Should be taken of the fact that there is currently a process underway to extend RHS to Geo-RHS. By explicitly taking account of geomorphology this may be an appropriate approach to assessing hydromorphological processes.
It has to be recognised that whatever approach is adopted it will be necessary to set up a system of accurately recording data, developing standard recording methods and implementing appropriate QA procedures.
Less work has been done on approaches for lochs, transitional waters and coasts. The lake equivalent of the RHS, a Lake Habitat Survey (LHS), is currently under development. It is expected to provide a basis for providing an approach to lakes.
In transitional and coastal waters there is no equivalent to the RHS. The existing classification systems applied by SEPA in transitional and coastal waters primarily focus on the achievement of water quality objectives and ensuring that biological quality is not impaired. The closest existing regime is probably the setting of conservation objectives for European Marine Sitesunder Regulation 33 of the Habitats Regulations. There is a need to develop monitoring tools that can detect changes in ecological elements related to hydromorphological modifications. Such tools should, therefore, as a minimum, be able to assess and be sensitive to:
between types of ecological
element within a water body,
Changes in extant (absolute abundance) of ecological elements within a water
Changes in composition an abundance of all ecological elements within a water
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