Planet WGSW-24010 User Manual page 51

Box 4 Non-standar d sur vey lengths
1. Exceptions to the standar d 100m sur vey length
If it is absolutely impossible, in a large river, to find two 100m sites of comparable
character within close proximity of a discharge being assessed then choose 50m
reaches of similar character, provided that the river is at least 10m wide (so that the
survey area will be >500m
2. Optional sur veying of 500m sur vey lengths, in addition to the 100m length
Where extra information would assist in the interpretation of data, the surveyor has
the option to undertake a 500m survey in addition to the standard 100m length survey.
The 500m (which must include the original 100m survey length) is surveyed in its
entirety as a separate survey, using a 5-point scale for recording macrophyte
abundance rather than the 9-point scale used for 100m surveys (see 4.5.5 for
abundance scales). It is not possible to convert the data collected from the initial 100m
to the 5-point scale and combine this with data collected for an additional 400m. The
MTR is not affected by the use of the 5-point scale in place of the 9-point scale but
more information and more resolution of abundance changes can be gained by using
the 9-point scale.
The additional 400m can be placed at either end of the initial 100m or split either side
of it according to site circumstances to give a continuous 500m survey length. Gaps
between the survey lengths are not allowed.
The aim of carrying out the 500m survey is to obtain a fuller species list in order to
verify the interpretation of trophic status from the 100m survey. In many cases the
500m survey will act as a 'quality check' on the location of the 100m survey length. In
such cases, a 'working' MTR may be calculated from the 500m survey data, but this
must only be used to compare with other 500m 'working' MTRs (eg upstream-
downstream pairs) and to verify that the interpretation of trophic status from the 100m
survey(s) is correct. In most cases, the MTR calculated from a 500m survey will not
be significantly different from that derived from a 100m survey. As a precautionary
measure, however, 'working' MTRs from 500m surveys SHOULD NOT BE USED
for reporting purposes.
If a 500m survey is carried out, this does not need to be re-surveyed every year but
may be repeated every 5 years for comparative purposes IF great changes in the 100m
survey data occur.
R&D Technical Report E38
2
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