Page 22 - Freshwater-Biology-and-Ecology-Handbook

DEVELOPMENT

River habitat improvement is a fundamental component One of the more important early attempts to enumerate
of river restoration. Often, the chemical pollution has been biological quality in the UK was the Trent Biotic Index,
improved, but habitat remains unfavourable. Significant developed by Woodiwiss in 1964, to assess the quality of
progress is being made into options for river restoration the River Trent and other rivers in the British Midlands.
(7)
and habitat improvement. Many rivers were widened and This assessed the presence and absence of sensitive
deepened (resectioned), straightened and river banks invertebrates to polluted environments and allowed the
stabilised with concrete or other material, to promote environment to be described as an index ranging from
drainage. In the UK about 10% of the Environment Agency’s one to ten, one being the most polluted and ten the least
engineering budget is now spent on restoring river channels polluted. This and similar biotic indices were utilised
by removing these structures and recreating natural extensively by biologists and river managers for many
meanders to restore ecological quality. Weirs and other years. However, the Trent Biotic Index was insensitive
impoundments to fish migration are being removed to not to a number of situations and pollution types and more
only restore fish populations, but also to meet specific sensitive systems have since been developed.
legislation, such as the Eel Regulation 2007 (5)
In 1970 Chandler took these concepts and added a semi-
The River Restoration Centre based in the UK at Cranfield quantitative component or weighting which transferred
University, holds significant resources and expertise on this. presence and absence of indicator organisms into a scoring
(8)
system – The Chandler Score. This provided a numeric
Regulators have been slow to adopt biological assessment basis for the classification of polluted waters and is the
methods, possibly because of the cultural links to precursor of the current biological monitoring and evaluation
engineering and chemical disciplines of developing industrial scoring systems. The Chandler score was sensitive to both
and regulatory organisations. In addition, the complexity organic pollution from sewage, and toxic pollution from
of biological systems is difficult to communicate to wider industrial discharges and acidic mine drainage.
audiences and to link directly to cause and effect. Translating
complex indicators of water ecosystem health into simple One of the most established systems of biological
indexes and regulatory tools has been problematic. assessment is the Biological Monitoring Working Party Score
(BMWP), which underlies river invertebrate assessment
One of the earliest significant attempts to systematically methods in the UK and many European countries today
(9)
assess river health was the Saprobic Index developed (BMWP, 1978 ; Hawkes, 1997 (10) ). This index was designed
(6)
by Kolkwitz and Marsson in the early 1900s. This was as a national system suitable for the biotas of all types of
a system of categorising water quality through levels of rivers in the UK, being devised for the National River Quality
organic waste (pollution) in rivers and streams. It was based Surveys. Like the Chandler Score on which it was based, it
upon the abundance and distribution of biological species in was sensitive to a wide range of pressures.
four saprobic zones. This methodology has been extensively
developed in continental Europe and is still used for Water
Framework Directive assessment in Austria and Germany.

22 | Freshwater Biology and Ecology Handbook
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