DEVELOPMENT OF A TECHNIQUE FOR
LAKE HABITAT SURVEY (LHS):
PHASE 2
WFD42
June 2006
EXECUTIVE SUMMARY
This research project reports the second phase of
development of the Lake Habitat Survey (LHS) method, building on the
results of the Phase 1 project (SNIFFER Report WFD40, 2004).
The need for the work arose from the recognition that within the UK and
across Europe more generally, no standard methods existed for assessing
the hydromorphological condition of ponds, lakes and reservoirs, or for
assessing the physical condition of standing waters in sites designated
for conservation. The European Water Framework Directive (WFD),
introduced in 2000, has acted as an important driver for LHS,
especially because the WFD places a high premium on the development of
international standards (e.g. those produced by the European Committee
for Standardization). The utility of LHS to provide input
data into decision-support systems required for environmental standards
was therefore fundamental. However, from its inception,
because of the limited choice of available methods, it was recognised
that there was scope for this new scheme to be multi-purpose, providing
data for management and conservation applications, systematising
environmental impact assessment and supporting restoration programmes
for degraded lake ecosystems.
The protocol underwent some minor revisions following an expert
workshop in March 2005, with further amendments made following training
workshops held at four lakes across the UK. The final
July-2005 versions of the field form and manual were tested both by
contractors and partner environmental agencies (EA, EHS and SEPA)
during the 2005 field season (available from the SNIFFER website).
Field trials were also conducted in several European countries
including Ireland, Finland, France, the Netherlands, Poland and
Serbia-Montenegro. Dialogue between surveyors and contractors
proved vital for refining the protocol, improving the consistency of
field results and improving surveyor confidence.
In terms of methodological development the two main areas considered
were the sampling strategy (i.e. the number and siting of Hab-Plots)
and further consideration of the role of remote sensing. For
selected sites (Loch Lomond, Loch Earn, and Barton Broad) large numbers
of Hab-Plots were collected (38, 15 and 18 respectively), allowing
surveys of various size to be simulated with the data. It is
demonstrated that the uncertainty in Hab-Plot summary data diminishes
with sample size, but it was concluded that minor gains in precision do
not necessarily outweigh the benefits of a standardised procedure,
particularly when considered in tandem with the perimeter survey
results. Viewed in the context of a hierarchical monitoring strategy it
is concluded that the standard protocol of 10 evenly-spaced Hab-Plots
should be the default method. Where surveillance monitoring
suggests particular issues or complexities within a system,
investigative monitoring can pursue further samples (in increments of
10 and maintaining the principle of even spacing). Further
consideration was given to the use of remote sensing and GIS tools. The
use of aerial photographs and high resolution digital maps were
complemented by an airborne hyperspectral survey of Torside Reservoir.
It was concluded that remote sensing is best considered as a
complementary method, rather than as an alternative, to a field-based
assessment. Analytical and sampling uncertainties, however,
are minimised in the field when surveyors have access to high quality
maps and appropriately-scaled air photographs.
Following the 2004-05 field seasons the LHS database now contains c.
200 lake surveys (comprising c. 1400 constituent Hab-Plots). Useful
summaries relating to engineering practices as well as the range and
intensity of specific pressures can inferred, with the caveat that
these data do not comply with the statistical requirements of a
probability-based, area-weighted sample (though this is desired in
future). Summary metrics, such as the Lake Habitat
Modification Score (LHMS) and the Lake Habitat Quality Assessment
(LHQA) were also derived. LHMS scores of zero were recorded
at c. 5 % of sites within the UK, indicating that these would qualify
as being at reference condition with respect to hydromorphological
quality elements. A useful distinction was made between
hydrologically ‘regulated’ and
‘un-regulated’ sites, with the former showing
consistently higher LHMS scores and a much wider range of specific
pressures. LHQA results were more equivocal, and demonstrated
strong scale-dependency, with larger sites such as Loch Lomond having
high levels of hydromorphological alteration, but by virtue of their
large size they also still contain extensive and diverse natural
habitats giving them a higher assimilative capacity with respect to
pressures. Analysis of LHS data showed links between
macrophyte structure (serving as a proxy for functional groups) and
substrate characteristics, which in turn was related to geology and
effective fetch. It is concluded that there is considerable
potential in analysing the structural data within the database to make
inferences about lake habitats. However, further investigations into
the linkages between hydromorphological alteration and ecology were
constrained by limited access to appropriate biological data.
In terms of the next steps in LHS development, it is concluded that the
key challenge remains in more fully exploring the relationships between
LHS metrics and comparably scaled biological data. It is
noted that integrated field campaigns where macrophyte,
macroinvertebrate and fish data have been collected at the same time as
LHS surveys offer particular opportunities to advance in this
direction. The need for further training and an accreditation programme
that will ensure consistency of approach in both field data collection
and metric calculation is also recommended. Further innovations
relating to the development of electronic field forms, negating
database transcription errors and permitting real-time generation of
summary metrics inclusive of uncertainty, are further targets for the
Phase 3 development of the LHS assessment tool.
Key words: Lake Habitat
Survey, Hydromorphology, LHMS, LHQA, Water Framework Directive,
Habitats Directive
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