Interpretation Of Mtr Results; Interpretation For The Purposes Of The Uwwtd - Planet WGSW-24010 User Manual

6

INTERPRETATION OF MTR RESULTS

This chapter provides guidance on presenting and interpreting results from MTR surveys. It
focuses mainly on interpretation for UWWTD purposes but also considers other applications.
6.1 Inter pr etation for the pur poses of the UWWTD
6.1.1 Gener al
The aim of using the MTR in the context of UWWTD monitoring should be borne in mind at all
times when interpreting MTR results and preparing these results for presentation. This aim is
to provide evidence of:
i) eutrophication impact on macrophyte communities in order to support designation of
reaches as SA(E); and
ii) the specific impact of qualifying discharges on such reaches.
MTR assessments are only one aspect of the considerations needed to identify SA(E)s and all
other supporting data should be evaluated before final recommendations are made regarding
potential candidates. These data can include overall percentage macrophyte cover, other
biological data (such as TDI/DQI), chlorophyll data and chemical data. Account should be taken
of known management practices and impacts on the site(s).
6.1.2 Pr esentation of Results
Results from MTR monitoring undertaken for UWWTD purposes will comprise a number of
surveys over a period of years at each site (usually 3 or 4 surveys over 4 years) and a minimum
of two sites per QD, one upstream and one downstream. Each group of surveys carried out at the
same time, ie within a few days but at different sites, is termed a 'set' of surveys, for the purposes
of this guidance.
Information from MTR surveys should be presented in a concise, accurate and consistent format.
To achieve this, a standard approach to data presentation and interpretation should be adopted.
For UWWTD purposes, this approach should comprise the following elements.
1. Present results as actual MTR scores (to one decimal place), together with the percentage
downstream change in MTR downstream of a qualifying discharge. Present results for
each set of surveys; do not average results to obtain a mean for the period monitored.
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