Ecoregion typing

• Ecological classification or typing will allow the grouping of rivers according to similarities based on a top-down nested hierarchical approach.

• The purpose of this approach is to simplify assessments and statements on ecological water requirements.

• One of the advantages of such a system is the extrapolation of information from data rich rivers to data poor rivers within the same hierarchical typing context.

Taken from: Dr N. Kleynhans

EcoregionsIn this approach, ecoregions are regions of relativehomogeneity in ecological characteristics or inrelationships between organisms and theirenvironments.

 

Level I: This level of typing is based on the premise that ecosystems and their components display regional patterns that are reflected in spatially variable combinations of causal factors such as climate, mineral availability (soils and geology), vegetation and physiography (Omernik, 1987). In South Africa, physiography, climate, geology, soils and potential natural vegetation, have been used as the delineators of Level I. Level II: The same characteristics as for the Level I typing is used, but in more detail. Level II typing will produce regional or sub-catchment scale ecotypes. Level II will be a suitable stage to link to stream classification.   Taken from: Dr N. Kleynhans

 Omernik's (1987) approach is based on patterns of terrestrial RIVER TYPING

ECOREGION TYPING

LEVEL I ECOREGION ATTRIBUTES

PHYSIOGRAPHYCLIMATEGEOLOGY AND SOILSPOTENTIAL NATURAL VEGETATIONHYDROLOGY

LEVEL II ECOREGION ATTRIBUTES: SAME AS LEVEL I, BUT MORE DETAIL

PHYSIOGRAPHY (Terrain morphology, relief altitude)CLIMATE (Rainfall (MAP), Rainfall seasonality and variation, Temperature)GEOLOGY AND SOILS (Lithology, Rock types, Soils)POTENTIAL NATURAL VEGETATION (Vegetation types (Low & Rebelo)HYDROLOGY (MAR, Median runoff, variation)

STREAM CLASSIFICATION

GEOMORPHOLOGICAL SEGMENTS

LONGITUDINAL ZONES

BIOLOGICAL SEGMENTS:

Fish Habitat SegmentsInvertebrate Habitat SegmentsRiparian Vegetation

Taken from: Dr N. Kleynhans

River Complexity

physicalsystem

biologicalsystem

geomorphology

hydrology

botany

zoology

ecology

Management of aquatic systems

Species distribution

Abundance

Community structure

Resource use

Consumption

Distribution

Cultural value

Beauty

“sense of place”

Economic development

Social/human welfare

Evironmentalprotection

Adapted from Roux, 1999

Lazorchak et al., 2002

Lazorchak et al., 2002

Fish as bio-indicators

• The relative health of fish communities are sensitive indicators of direct & indirect stresses on the entire aquatic ecosystem (Karr, 1981).

• Fish are useful indicators for biomonitoring and flow assessment studies. (See Karr, 1981; Fausch et al., 1990; Karr & Chu, 1999, Kleynhans, 2003; Louw, 2003).

• A biological index integrates and summarises the biological data within an indicator group.

• Biological indices therefore quantify the condition of river health with a numeric output (Karr, 1999).

Fish Assemblage Integrity Index (FAII)• Karr’s Index of Biotic Integrity (IBI) detects divergence from

biological integrity caused by human actions by using fish community parameters.

• FAII developed by Kleynhans (1999) for SA rivers.• Compares aspects of expected & observed fish assemblages• This index categorises fish populations according to an

intolerance rating which takes into account trophic preference and specialisation, flow requirements and association with specific habitats and unmodified water quality.

FAII cont. – Results of the FAII expresses as a ratio of observed vs. expected

conditions

• FAII(EXP)=IT((F+H)/2; FAII(OBS)=IT((F+H)/2• Relative FAII=FAII(OBS)/FAII(EXP) x 100

– Interpretation of FAII scoreTable 3.2 Fish Assemblage Integrity Index assessment classes (Murray, 1999).

FAII Score Class Description90-100 A Unmodified or approximates natural conditions closely80-89 B Largely natural with few modification60-79 C Moderately modified40-59 D Largely modified20-39 E Seriously modified0-19 F Critically modified