Rapid Validation of WFD83
Standards for Freshwater Flows to Estuaries
WFD83 Ext.
February 2008
Introduction
Background
The WFD 83 project (SNIFFER 2007) proposed a set of freshwater flow
standards transitional waters in the UK. These have been defined to
protect estuaries from modifications in freshwater flows resulting from
pressures in theupstream catchments (abstraction). The flow standards
aim to support Good Ecological Status as well as Moderate Ecological
Status.
The standards assigned to transitional water bodies depend on the
sensitivity of the estuary to abstraction impacts. This sensitivity has
been defined in WFD83 using factors such as freshwater inflow and
estuary volume (tidal prism). Each set of standards (i.e. for each
level of sensitivity) allow a net level of abstraction from the major
(Code 1) freshwater inflows (i.e., in the upstream catchment) for flows
of >Qn60, >Qn70, <Qn95 and >Qn95. Code 2
inflows are given a generic set of flow standards regardless of estuary
sensitivity, again for each of >Qn60, >Qn70, <Qn95
and >Qn95.
Aims
One of the recommendations from WFD 83 was to validate the proposed
flow standards with actual measured data. As a result this project
presented here has firstly tested where these standards pass or fail in
estuaries, i.e., based on influenced (to approximate actual) flows; and
then assessed these results against pressures and specific ecological
data. In doing this, the results (i.e., pass or fail in flow standards
defined for a particular estuary) have been compared to available
environmental information to see whether these are in support. I.e., in
a failure we would expect to see environmental impacts of degradation
whilst for a pass, we expect a healthy environment.
Report Chapters
The work carried out has been divided into the following chapters:
- In Chapter 2 an account of flow standard pass / failure is
given as part of the hydrological assessment;
- Chapter 3 provides a comparison of these flow standard
results against WFD pressures data;
- Chapter 4 reports on the comparison of flow standard
results with WFD monitoring pilot studies;
- Comparisons between flow standards results and fish data
are given in Chapter 5; and Chapter 6 provides a conclusion and
recommendations from the study.
Copies of this report are available from the Foundation, in electronic
format on CDRom at £20.00 + VAT or hard copy at
£25.00, less 20% to FWR members.
N.B.
The report is available for download from the SNIFFER Website