Page 50 - Freshwater-Biology-and-Ecology-Handbook

CHAPTER 1 4.4 4.4 Typology

Typology, or surface water type, describes the physical and physico-
chemical characteristics of a water body that determines the sorts of
plants and animals that would be present under natural conditions.

Water body typology therefore defines the biotas at reference
conditions and therefore the reference values against which biological
quality is measured.

Different types reflect the geology, morphology, climate and Typology is an essential component of surface water
altitude of water bodies, all of which define the reference classification systems. For each surface water type an
flora and fauna. In this way, a typology map of each river estimation can be made of what the biology would be
basin can be built up, using Geographical Information if there were no (or very minor) alterations to the water
Systems, if possible, to inform the distribution of the body resulting from human interference. This allows the
monitoring network. Results from early monitoring can be fundamental concept of ‘Reference Conditions’ to be
used to build up an initial assessment. This typology can be established around which the classification systems will
refined as information increases. be developed.
The aim of river (or stream) typology is explained in the The WFD provides two methods for Member States to
(16)
AQEM project (AQEM consortium, 2002). River typology define their national typology:
is defined as:
A river type is an artificially delineated but potentially
ecologically meaningful entity with limited internal biotic and System A
abiotic variation and a biotic and abiotic discontinuity toward Eco-regions and some obligatory factors.
other types.
System B
River types might serve as ‘units’, for which an assessment No eco-regions, but obligatory factors are altitude,
system can be applied. A river type should always be defined latitude, longitude, geology and size; and there are
on the basis of natural or near-natural reference sites, since also optional factors. See Tables 1.6 and 1.7.
the comparison with undisturbed sites of a certain river type
allows defining and classifying different states of degradation.
Biological assessment requires sufficiently stable, integrated
river typologies, which consider both abiotic and biotic criteria.
The most prominent abiotic factors are river morphology,
geo-chemistry, altitude, river size and hydrology.

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